EP1713546A1

EP1713546A1 - Method and devices for fully controlling respiratory protection provided with assisted ventilation and based on the use of filters

Info

Publication number: EP1713546A1
Application number: EP05717543A
Authority: EP
Inventors: Rolland Marais; Gilles Marais
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-02-03
Filing date: 2005-02-03
Publication date: 2006-10-25
Also published as: FR2865654A1; FR2865654B1; WO2005082462A1

Abstract

The invention relates to a method and an assisted ventilation respiratory protection device (1) for controlling (19) the efficiency of filters (2), positive pressure (10) and tightness of a facial piece (22) by peripheral internal sampling (22.4) of a total (9.3, 9) or partial (9.8, 18) air return which is totally exhausted in the atmosphere on the entire device, the air supplied to (8) said facial piece and removed therefrom (9) by a turbine (5), the assisted filter and/or joints replacement during the use of the device by means of the permanent internal turns round part of an air filter (6) and appropriate devices (4, 3.1, 3.10) associated with permanent protection. The filtered air is sampled at the output (8.1) of the turbine or at the full (9.1) or partial (9.2) return towards selecting means (13) for selecting rate measurement means (16, 14), pressure measurement means (12), means for measurement of relatively humid substances (15) between the initial state at the exit from filters and the motion thereof during use and between an exit from filters and the full or partial return. The real efficiency of filters using said method and device corresponds to the efficiency determined by simulation of comparable situations on a test bench.

Description

Method and devices allowing total control of respiratory protection with assisted ventilation based on the use of filters

The present invention relates to a process implemented on a respiratory protection apparatus with assisted ventilation, allowing, in real use, total control of the uses of adsorption filters, of the real positive pressure and of the seal in a face piece; this process and its implementation on such a device also made it possible, in a complementary manner, to cross-check and validate a method of testing the effectiveness and the lifespan of such filters in simulated exposure situations on a bench.

Field of the invention:

The process and the respiratory protection apparatus with assisted ventilation (APRVA), objects of the present invention are applicable in the fields of respiratory protection, preferably with assisted ventilation, requiring a very high level of control of safety and operation taking into account counts the effects of humidity, to protect the health of people against any attack by substances for which there is a filter and, advantageously, detectors allowing the complementary measurement of such substances, including humidity. These areas are all those where the ambient air carries dangerous molecules or particles such as: industries manufacturing or implementing or using such molecules or particles, whether these industries are in a normal or degraded mode of operation or in situation crisis, protection against harmful gases spread by a belligerent (acts of terrorism or state of war), the fight against uncontained fires, certain natural phenomena such as for example volcanic eruptions, etc.

State of the Art Respiratory Protection Devices (RPDs) based on the use of adsorption filters are in common use against the risks linked to the inhalation of chemical substances. The effectiveness of the adsorption filters used varies according to many parameters, the main ones generally accepted are known to those skilled in the art: - the nature of the substances encountered and their physicochemical properties, - the nature of the absorbent used: specific surface or microporous volume, pore diameter, acidity or basicity, behavior with respect to water vapor, etc. - the humidity or the water concentration in the air and the air temperature, - the risk of interference between substances which can be the cause of selective adsorption and desorption phenomena, the case of humidity or water vapor concentration being a particular critical example.

This multiplicity of parameters, and the multiplicity of possible applications in the field, make it difficult to use and control such adsorption filters in respiratory protection. This difficulty is the main reason for the precautionary principle adopted by those responsible for prevention, who hesitate to prescribe them for respiratory protection against the risk of exposure, particularly for the many repetitive situations usually encountered. The guarantees offered by such filters have progressed steadily through the implementation by manufacturers of standardized tests. These tests indicate the general uses of these filters and their compliance with the minimum requirements contained in the standards. However, these standardized tests are carried out under specific conditions (fig. 1), most often very far from the reality of the situations or operating conditions encountered in the field (fig. 2). This way of operating the adsorption filters has many drawbacks, all of which are juxtaposed. The standards, and the manufacturers in an associated way because of the commitment of their responsibility, introduce important safety factors concerning the recommendations for use. In many cases, they refer the determination of the conditions for the actual implementation of these filters to the prescribers and their responsibility. Prescribers, directly confronted with this responsibility as an employer and with their regulatory obligations to provide means, also adopt in addition a "precautionary principle" prohibiting them from taking or managing the slightest risk. In many cases, filter users do not have a simple procedure adapted to the actual conditions of use. They use it anyway and at best throw away the filters after a single use, or at worst, when an odor is perceptible at the exit of the filters or at the end of a period of variable use rarely controlled. The organizations or institutions referent in the matter which, through the conclusions of numerous studies on the subject, set the limits of respiratory protection based on the use of adsorption filters, a fortiori with the masks with free ventilation commonly used. For example INRS in France in ND 2123-178-00 - documentary note book n ° 178, 1 ^st Mm. 2000), Certain referent organizations, in order to improve knowledge on the behavior and performances of filters, in particular in real exposure situations, have plans to carry out various studies. For example, INRS, in France, reports on its website a study project under the title: "Development of a set of benches for tests of compliance with CEN standards for respiratory protection filters gases and vapors "or another under the title:" Determination of exposure profiles to solvents and comparison with short-term limit values "; in these study projects, in addition to the necessary certification, the authors announce that they intend to test the filters by reproducing real conditions of use, on more complex substances or mixtures of substances, at different flow rates, taking into account account for the effect of humidity, certainly to better understand the reality of real exposure situations, certainly with methods comparable to those used in the tests shown in figs. 2 and 3 which are the basis of the process of the present invention. These examples of studies will better correspond to the reality of the situations encountered. It is common in industrial chemical processes to be confronted with the risk of exposure to mixtures of substances or, more simply, to strong variations in the concentration of a substance, this is the case for example during numerous maintenance operations with breach of containment, however, these variables are not taken into account in the standardized tests. This type of study will certainly improve knowledge practices on the real dynamic behavior of adsorption filters using an adsorbent according to physical sorption / desorption or chemisorption processes, however well known and commonly applied in many fields, for example industrial gas treatment and purification, gas sampling for pollutant analysis, etc. Quite paradoxically, the improvement of this knowledge does not necessarily lead to a simplification of the implementation of filters, this for a prescriber or a user whose essential objectives are: ease and safety of use, associated with strong request for operational expertise from organizations providing these filters in this type of respiratory protection. In the state of the art and current ordinary use practices, the finding of impossibility of perfectly controlled use of respiratory protection based on the use of adsorption filters, remains relevant. There is therefore a significant need in all the abovementioned fields to be able to fully use adsorption filters which are particularly effective in respiratory protection suitable for industrial hygiene and easy to use. It is also necessary for any manager, beyond their obligations of means, to show that the protections made available to their staff are effective, controlled and under control. There is, in addition, for intervention personnel or military personnel, the need to ensure maximum protection of the technological possibilities available to guarantee their operational capacity, in the face of the risks and threats of chemical or other attacks, and allow them to carry out their missions in all circumstances. It follows that the way of operating the adsorption filters must be re-examined on the merits. This examination must take into account several aspects of a different nature, sometimes contradictory, for the best possible result and a clear objective, decrease to the technological optimum, or better eliminate totally, the exposures. - professional in the current state of industrial processes, which consequently requires to continue to improve them, - or operational with regard to intervention personnel or military personnel. This implementation must be done according to a process which must be: easy to use, accepted by users, possible to control, economically bearable, and in addition to being discreet. Faced with this problem, the majority of manufacturers offer Respiratory Protection Equipment with Assisted Ventilation (APRVA) regulated electronically or by microcontroller. These devices are based on the use of adsorption filters. The best have, apart from the filters, protective characteristics comparable to those obtained with Self-Contained Breathing Apparatus (ARI), for a weight approximately 10 times lower and often much better ergonomics and average autonomy. An example of this type of APRVA equipped with two filters was used for the tests on the basis of the process of the present invention, its flow rate is adjusted during construction to a minimum value of 120 l / minute. The adsorption filters from a supplier used in the example tests based on the process of the present invention are of the AXP3 type approved for substances with a boiling point <65 ° C. and for a single use, generally in ventilation. free. They contain a charge of approximately 320 cm ³ of activated carbon with a specific surface of about 1200 to 1300 m ^z g, associated with a P3 filter to block dust and / or aerosols. They may however be suitable for a wide family of higher boiling point substances for which "standard" type A2 filters (tested according to class 2) are usually used. A2P3 filters contain approximately 220 cm ³ of activated carbon with a specific surface area comparable to that of AXP3, so they are a priori less effective than AXP3 filters. In general, the purpose of the tests is to guarantee users a minimum time of use under the flow and concentration conditions fixed in the standards, breakdown time after which the breakdown concentration indicated in the standards is reached at the filters outlet. In addition, certain time limits or conditions of use recommended by the supplier will be taken into account. A rule in order of magnitude is usually applied to evaluate, from this breakdown time, a time limit of use as a function of a different mean concentration measured. This rule is roughly established by extrapolation from the results of standardized tests, i.e. on the assumption of a constant concentration of a single substance at the inlet of the filters and the assumption of a total conservation of the mass of this substance on the adsorbent used, in other words the sole capacity of the adsorbent. It does not correctly take into account the dynamic behavior of substance (s) on the adsorbent, in particular concerning the effect of the humidity (water concentration) contained in the air when for example: the duration of use of the filters is increased, or this humidity increases, or that the uses are multiple, or the variations in concentrations of substances of the actual exposure situations, very far in most cases from the limits of the capacity of the adsorbent . The set: device + filters + face piece is normally subject to CE approval according to standards which assigns a classification of minimum performance which varies according to the face piece used and determines a Nominal Protection Factor. Although the performance of these face pieces is different from that of filters, the overall effectiveness of respiratory protection and the Assigned Protection Factor (APF) achievable in real situations largely depend on these performances. It is certain that the use of assisted ventilation significantly improves these factors compared to a Respiratory Protection Device with Free Ventilation (APRVL). This different problem must necessarily be taken into account in a re-examination on the substance of respiratory protection. It is recognized that the standardized tests, as summarized above, are not sufficiently suitable for Industrial Hygiene where the dynamic behavior of the substances on the filters, in particular with APRVA, becomes preponderant. This will be even more true for military uses for example where the concentrations of substances or aggressive agents, by nature very toxic, are most often encountered at low concentrations, even very low and dispersed, circumstances in which the only capacity can no longer indicate the applications of the filters under guaranteed safety conditions. Thus, for example, during dynamic tests carried out on the basis of the present invention with an APRVA and a unit air flow rate of 60 l / minute minimum, such filters have given in actual exposure situations operational performances clearly superior to those indicated in standards or notices. It is therefore above all on adsorption filters that the effectiveness of the implementation of these protections rests, and it is therefore at this level that their uses must be validated in real exposure situations or, failing that or additionally, tested in simulated exposure situations on a bench. It is then by total control of the operating conditions of such filters on devices that operational solutions can be proposed. Finally, it is at the level of a device that all of the means must be integrated to guarantee this efficiency and control. Some inventors and / or manufacturers have proposed solutions in order to better control the performance of filters and / or respirators and to be able to inform users about their necessary replacement. In document US 5 322058, the device described comprises recycling part of the air exhaled in the inspired air as a function of a maximum authorized content of CO2 (5000 ppm) in the mixture: fresh air coming from the filters- * - recycled air, offered to a user; the other part is released to the atmosphere through a three-way valve or continuous discharge valve system. Such recycling is carried out through a separate air return pipe coming from a face piece directly connected to a buffer bag, a conventional face piece always comprising valve and valve systems, generally disposed on said face piece; these valves or flaps remain essential for the proper functioning of the proposed device. On this face piece are conventionally connected an air inlet pipe and a separate air outlet pipe, arrangement notoriously suggested from the description in US Pat. No. 4,016,876, in FIG. 3b, of an example of a comparable device comprising such a separate pipe arrangement on a device, pipes necessarily connected to an identical face piece organized accordingly. The main objective of the proposed invention is to extend the theoretical life of the filters, however such a life is not directly and actively verified in the proposed device. The possibilities offered by such air return are therefore not completely operated with the aim of determining the real lifespan of the filters or of fully controlling the safe operation of the proposed arrangement. The second proposed objective consisting in saving the batteries of such a device is not clearly demonstrated and can no longer be retained in view of the technological evolution of the batteries available in the current state of the art whose autonomy exceeds largely in all cases of those filters that thereby again become the element limiting the duration of possible uses. In document US-6040777, the proposed technique is complex and uses a device independent of an APR worn by a user. Its main objective is to continuously assess a protection time or the supposed capacity remaining available on filters in order to inform a wearer about the replacement of filters. This evaluation is based on methods published by the Ai HA, the device used must be pre-configured on the case to be treated before any use. The proposed device cannot deal with the case of mixtures of substances since it evaluates a priori an unwanted variable at the output of the filters from data relating to a single substance and ambient measurements performed at the input of the filters. Even in the event that these measurements indicate the sum of the concentrations of substances, this would not ensure the desired dependability, each substance having a different complex behavior on filters. In document US 5,950,621, a method of managing breathing apparatus with assisted ventilation is proposed. The description of this method largely refers to means known in the state of the art for: identifying all or part of the components of such devices, operating and controlling these devices using different sensors processed by microprocessor. On the particular point of determining the life of filters, the objective of the proposed method is comparable to that described in document US-6040777. It consists, according to the inventors, by means of an appropriate device which could be placed in a device, to integrate the total volume of air passed over the filters to assess their protection time or their remaining available capacity; the notable difference compared to document US-6040777 is that no measurement is practiced in the ambient atmosphere during the use of the filters what makes even more dependable the desired operational reliability. In document US-6162281, the technique used is complex and requires modification of the filters. Its main object is to anticipate the end of the effectiveness of such a filter by practicing measurements on the air taken from several zones of the adsorbent relative to a concentration measured in the inlet zone, concentration taken as a floating reference with the aim, according to the authors, of compensating for the zero drifts of a detector. Besides the necessary modification of the filters to their construction, such a method can only work if the concentration of substance is moderately stable at the inlet of the filter, which is rarely the case in reality. In another document, a device has been proposed comprising an optical fiber integrated into the construction of the filters to indicate the degree of saturation in substances of such filters. This device, according to its authors, is not very sensitive and has a relatively rapid aging due to the humidity of the air. Document EP-0838243 describes a process for fixing undesirable substances contained in the air on a support previously impregnated with a substance chosen for its odorous and non-harmful properties. The odorous substance is displaced by the undesirable substances to be absorbed above a certain saturation threshold of the absorbent. The odor perceived by a user makes it possible, according to the inventors, to determine the end of life of such a support. In document US Pat. No. 6,575,165, it is essentially a question of a method and devices for the rapid connection of filters between a respiratory device and such filters, physical locking of such a connection and its verification by various means, including one electrically. driver. The inventors suggest that such locking effected by lugs could serve to close a contact as soon as a filter is correctly in position, that the failure to make such a contact could usefully condition the operation of the fan and / or other additional functions mentioned, for example the use of such a contact for hot filter replacement. The mention in this document of the hot replacement of such filters, a delicate operation certainly presenting great risks, cannot be criticized in this document for lack of a device or proposed method. In general, among all the solutions proposed in the state of the art examined, the tightness of the face pieces is always affirmed but never actively or directly verified. In general, the solutions proposed show the current trend towards more complex face pieces, thus making them more fragile, more costly to purchase and maintain, with the consequence that an ATEX classification is certainly more difficult to obtain and a ""lessdiscreet" functional signature.

The object of the present invention is to remedy the majority of the aforementioned drawbacks or to improve certain existing devices. Statement of the invention. The subject of the present invention is a method and a device for implementing this method, integrated into an APRVA, allowing total control of the use of adsorption filters, or filters in general, in particular their real lifespan, total control of the protection offered, total control of the operation of such an APRVA. According to the method of the invention, one collects laterally or peripherally inside a face piece produced for this purpose all of the air preferably sent therein by a respiratory assistance system filtering said air, all of said air collected is returned to said respiratory assistance system in order to reject it entirely to the atmosphere remotely at said respiratory assistance system; said air collected inside such a face piece is returned entirely by an appropriate line to said respiratory assistance system and said total air return is used for the measurement or the control of several operating parameters of said method and said respiratory system by the implementation of operations or means suitable for the measurements or controls operated with the objective of controlling the effectiveness and the duration of use of the filters, the tightness of such a face piece and the safe operation of such a respiratory assistance device. This device is also remarkable in that it preferably comprises a pipe for the total return of air to the APRVA, for example constituted by a concentric pipe internal to the air delivery pipe or by a separate pipe. This device is also remarkable in that, in a variant, said air return can be produced in such a way that it constitutes a partial return, offering however, there is less possibility of controlling such a respiratory assistance system. This device is also remarkable in that it continuously comprises a circle of a portion of said filtered air as close as possible to the discharge and suction points. of the assistance means and a particular point between the filters and the suction of the assistance means and such a circle is used in controlled sequences of safety functions and / or assisted replacement of filters or seals , without losing the benefit of protection. According to the invention, the method is designed to behave in such a way that it performs one or more of the following steps:

- select at the outlet of the filters the said air delivered to such a face piece or the said air return, total or partial, of said face piece, for the purposes of measurements or functional checks on different parameters

- measure, parallel to said selection or independently of said selection, the air pressure on said air return, total or partial, relative to said delivered air or relatively to atmospheric pressure, and the air flow on said total return of air relative to the flow rate of said delivered air,

- Control and adjust the actual positive pressure available in such a face piece, in the case of a total return of air, by acting at the level of said respiratory assistance system on said total return of air;

- measure differentially from said air delivered, in the case of a total air return, on said total air return the instantaneous and / or average air demand of a carrier;

- Differentially calculating between said total return of air and said delivered air, the total leakage rate of air to the atmosphere of such a face piece;

- control and adjust the flow rate of said air delivered so as to maintain a flow rate at least equal to the sum of the flow rates: [air demand from a carrier + total air leakage to the atmosphere + an additional, fixed or advantageously proportional to said air demand];

- Differentially measure the concentrations of substances at the outlet of the filters on said supplied air, between an initial state observed when the filters are put into service and the evolution of this concentration during actual use, in absolute value and / or in drift per unit of time, to determine its efficiency instantaneous and the duration of use limit, said substances comprising the relative humidity of the air, said relative humidity including a temperature measurement;

- alternately measure by means of said selection the concentrations of substances in said total or partial air returns, and said delivered air;

- Differentially calculate the leakage in substance towards the interior of such a face piece, therefore the actual exposure to substances with the wearing of protection, independently of and in addition to the breakdown concentration of substances measured on said delivered air; and controlling this leak by acting on said respiratory assistance means;

- Carrying out a continuous and constant turn around of part of the filtered air between the suction and the delivery of said respiratory assistance means, for example a ventilator, for the purpose of carrying out controlled sequences for securing said safety respiratory support system.

- actively check or control, for example by means of a seal specially made for this purpose: the seal produced by such a seal between a filter and its support, the clamping pressure exerted on such a seal, the manual perception of the end normal clamping of a filter on its support, the normal presence of a filter on its support, through such a seal;

- maintain sufficient protection on a single filter or on the remaining filters, after detection and isolation of a filter and / or such a worn or defective seal in the event of degraded operation of said assistance system involving at least two filters and using said ordered sequences

- inform a wearer without being interfered with by his environment and without signaling him in his environment by the sole use of very low frequencies that are not audible;

- inform a wearer about the only faults relating to the maintenance of his protection with a simple and assisted action request to keep or restore this protection, supplemented for example by a local display and / or the recording of such information

- carry out the optional and assisted replacement of one or more filters and / or one or more filter seals in an emergency situation, while retaining the benefit of protection by using said ordered sequences; - maintain sufficient protection, in said case of said total return of air, in the event of failure of said respiratory assistance system, for example the ventilator, using such a face piece not equipped with valve, valve or other so-called demand devices d 'air;

- supplement respiratory protection with skin overprotection using such a total return of air normally put into the atmosphere in its entirety by capturing it at the outlet of such a respiratory assistance system, by occasionally and locally adapting to said face piece such over-protection of the access or transfer airlock type, for example for drinking, eating, providing care, etc., or more completely a hood or a ventilated suit, establishing controlled ventilation of such overprotection by a like APRVA

- cross-check the determination of the real efficiency of the filters as shown by such a process on such a device, by a method of simulating situations of extreme and average exposures, carried out on a bench; such a method taking into account the effect of humidity can be generalized to respiratory protection without respiratory assistance. The method and the device according to the invention provide numerous advantages. Implemented on such an APRVA, they make it possible to control the effectiveness and the real performances of the filters alone, by the use of detectors of suitable interchangeable substances integrated into the functioning of such an APRVA and the measurement of the concentrations of substances, including including the relative humidity, on the air sent after the filters to a face piece worn by a user, by a differential method between an initial state recorded when an APRVA is put into service and any subsequent state occurring during real uses, measured in absolute value and / or in drift per unit of time; they thus make it possible to determine the end of life of the filters and eliminate the problems of drift of the detector or of the need to use a reference, reported in certain documents of the state of the art. Implemented on an APRVA, they also allow the verification of the tightness of a face piece by the use of the same detector integrated into the operation of such an APRVA by practicing, by means of selection, differential measurements. concentrations of substances between the air sent after the filters to such a face piece and the air returning, totally or partially, from such a face piece to such an APRVA; it is no longer the Assigned Protection Factor which is thus determined, since it is no longer useful to carry out measurements on the ambient air, but the actual individual exposure with protective port, that without accessory or additional device to be worn by a user other than such an APRVA equipped with such a face piece, with better objectification of the reality of the results obtained. Implemented on such an APRVA, they allow not only the measurement, but also, according to the preferred embodiment with total air return, the control and the maintenance of a real positive pressure in such a face piece by such an APRVA which comprises a means for regulating the pressure measured on said total return of air from such a face piece, even in the case of significant leaks on such a face piece; such a face piece comprising no mechanical member, valve or valve is robust in construction and is not subject to regulatory inspection or visit. Such a face piece eliminates the risk of inward leakage associated with the valves or flaps usually located on the majority of the face pieces, in the immediate vicinity of the inhaled air zone and directly in contact with the ambient atmosphere. According to such a preferred embodiment with a total return of air, these risks of leaks are moved to a distant distance on the respiratory assistance system and, if they did occur, could never backscatter into the area of inhaled air, account given the permanent air flow rate applied in such a face piece. Implemented on such an APRVA comprising such a face piece, they also make it possible, according to such a preferred embodiment with total return of air, not only to measure the flow of air delivered to such a face piece but also to measure the air return flow rate of such a face piece, thus monitoring and continuously adapting the operation of such an APRVA to the average, or instantaneous, air demand of a user measured as being proportional to the deviation of the extreme or average flow rates between the inspiration and expiration phases, increased by a heel value which can be fixed or advantageously a function of such air demand, making it possible to achieve maximum periods of use of the filters, in particular in the standby at rest or survival position of a carrier; similarly, the total leakage rate to the outside of such a face piece is controlled by the difference between the flow average measured on the outlet of the filters and the average flow measured on the total air return of such a face piece. Implemented on such an APRVA, they allow, according to such a preferred embodiment with total air return, the maintenance of sufficient protection to be able to leave without risk a risk zone in the event of total breakdown of the ventilation system, even with the use of such face pieces, having neither valve nor valve. Implemented on such an APRVA, they also make it possible, according to the variant embodiments comprising at least two filters, with or without total or partial air return, and comprising a continuous circular motion of a low air flow rate between the fan output and the filter outputs, automatic safety functions and maintenance of the protection in a degraded operating mode on at least one filter if certain conditions are met, for example: substances are detected on the output of the filters, more precisely on a filter and not one (s) other (s) or in higher concentration on a filter compared to one (s) other (s), a tightening fault or the presence of a filter is detected by a tightness sensor and tightening force limiter joint; said automatic locking functions include a timed controlled return to a normal operating mode after correction of the fault and verification of the states. Implemented on such an APRVA, they still allow, according to the variant embodiments comprising at least two filters, with or without total or partial air return, and comprising such a turn in circles, the use of said setting functions. automatic safety triggered by the voluntary manual loosening of a filter for an assisted filter replacement function, or the replacement of such a filter seal which is possible on such an APRVA if, after the replacement of the filters, the substance continues to be detected specifically on the output of a filter, preventing the controlled return to a normal operating mode. As previously, said assisted replacement function includes a timed controlled return to the normal operating mode after correction of the fault and verification of the states. All filters can thus be successively replaced in any emergency situation, without losing the benefit of protection or risking contaminating the lines which remain pressurized and doubly blocked under sweeping air through a deliberately limited leak on a mechanical shutter valve in contact with the outside. Contrary to the method simply mentioned in the document US-6575165, in the said automatic locking functions and / or in the said assisted filter replacement function, the fan is never controlled or stopped by the contact established through the said seal. tightness detector and clamping force limiter, attesting to the presence of the filter on its support. The fan air flow remains controlled and adapted to the air demand of a carrier, it can be reduced or increased according to other programmed or measured parameters. This method and such an APRVA preferentially use a method of informing the user based on the use of a resonator at very low frequencies that are not audible, transmitting such vibrations directly to the column of air sent to the face of the patient. user in such a face piece, or transmitting such vibrations directly to a vibrator connected to such an APRVA and placed as close as possible to the contact of the skin of a wearer. This method, which does not require sight or hearing, resolves the question of users who are visually impaired, hard of hearing or with reading difficulties, whether these disabilities are preexisting or consecutive to an accidental or operational impairment of these capacities; such a method solves the problem of use in noisy areas where the wearing of hearing protection is necessary and also greatly reduces the functional signature, in particular visual and auditory, of the devices of the present invention for military uses. Such a face piece has no connection or electrical or electronic accessory, which makes it possible to envisage an easier ATEX classification for use in zones with risk of flammability. Implemented on such an APRVA, they do not require any modification or transformation of the filter production chains as has been proposed in certain cited documents. The devices and means used are fully integrated into such an APRVA, and are thus effectively protected. Implemented on such an APRVA, they allow, according to such a preferred embodiment with total return of air collected at the outlet of such an APRVA and connected to an overprotection, before being discharged to the external atmosphere to complete the respiratory protection of a wearer by partial skin protection in occasionally and locally adapting such an overhead protection such as an access or transfer airlock to said face piece, for example for drinking, eating, providing care, etc., or more completely a hood or a suit ventilated from such a total return of collected air, establishing controlled ventilation of such overprotection with such APRVA advantageously placed in all cases outside of such overprotection.

The results obtained with such a process applied and tested on real exposure situations are exactly cross-checked by a method of simulating comparable situations on a test bench, according to a claim, from direct injection of quantities of pure substances, separately or in the form of mixtures, without the need to manufacture costly and time-consuming standard mixtures. Such a method and such a bench make it possible to generalize bench tests in all cases of using filters, with or without assisted ventilation, on any type of support and for any substance. Such a test bench makes it possible to examine and take into account the potential consequences of extreme operations, such as for example the effect of high peaks of concentration of substances, the complex effects of humidity or exceeding the durations of recommended use. The invention will be better understood with the aid of the following description relating to a currently preferred form of implementation of the method and of its variants, as well as with the aid of the appended figures making it possible to understand the operating principles thereof. through some examples of implementation. Throughout the description and in all the figures or drawings, the functionally or physically identical parts have the same root and / or the same reference number. It should be understood, however, that the invention is not limited to the examples and the material means described or shown, nor to the number of filters which would be used with a comparable method implemented on a similar device.

FIG. 1 shows an example of recording a drilling curve in the case of a test carried out according to CE standards. Figure 2 shows an example of recording a substance concentration measured on real exposure situations.

Figure 3 is a schematic view illustrating an example of APRVA of the state of the art modified by the addition of two recording detectors to test the efficiency and the real behavior of the filters.

Figures 4a and 4b illustrate examples of state-of-the-art face pieces of the visor and full face mask type.

Figure 5 is a schematic view of preferred implementation of the method and its variants with total or partial air return by a concentric pipe, or total air return by a separate pipe.

Figure 6 is a schematic view of a preferred embodiment of a

APRVA with total air return by an internal concentric pipe, for use with a face piece, produced as shown in fig. 7

FIG. 7 shows a preferred embodiment of a face piece with internal peripheral air collection and its total return by an internal concentric pipe, for use with an APRVA produced as shown in FIG. 6

FIG. 8 shows an example of a preferred embodiment of a face piece with total return of air by a separate pipe, for use with an APRVA produced according to a variant of FIG. 6, in which the total air return is directly connected by means of pressure regulation, as shown in FIG. 5.

FIG. 9a is a detailed view of a schematic nature of the gasket detector and clamping force limiter of the filter on the air inlet in all the examples of preferred implementation of the method and its variants.

Figure 9b is a schematic detail view of the mechanical shutter valve on the air inlet in all examples of preferred implementation of the process and its variants.

Figure 10 shows examples of exit time curves measured in real exposure.

Figure 11 shows an example of overlap of the exit time curve and the resolution of a substance, obtained by a method of simulating real situations.

Figure 12 shows an example of a filter's back-sweep curve after simulated or normal use Figure 13 is a schematic view illustrating a preferred embodiment of a bench for tests in simulated exposure situations made from pure substances, and its main parts, Figure 14 shows an example of resolution curves of an example of a substance on such a test bench in simulated situations, for average concentrations between 2 and 20 times the average exposure value (VME) regulated or recommended not to be exceeded in average value for the example of substance chosen .

Figure 15 shows an example of a humidity and temperature variation curve quickly measured at the outlet of a filter if a significant quantity of substances is more or less suddenly adsorbed at the inlet of the filter, producing an "instant mirror image". "of the quantity of substances adsorbed. Figure 16 shows the phenomenological relationship that exists, in an example dealing with adsorption, between the molar fractions of different substances injected on the filter and the molar fraction of water displaced according to this "mirror" effect.

Reference is made to said drawings to describe interesting but in no way limiting examples of implementation of the method and production of the device according to the invention. In these drawings: - the arrows represented by a single solid line represent, in FIG. 5, the circulation of air, the thickness of the line is approximately in proportion with the air flows conveyed; - the arrows shown by a simple dotted line & strong dashed lines denote the APRVA service orders; - the arrows represented by a simple dotted line represent the data and information processed by a μProcessor which are useful for APRVA service commands; - the arrows represented by a single solid dashed line represent the alarm and information commands intended for the user and / or for deferred supervision; - the arrows shown by a thin continuous thin line and fine dotted line, designate the specific commands and data by means of substance measurement. The following abbreviations are used in the following description, for the sake of brevity:

VME: Average Exposure Value. Regulated or recommended not to exceed in average value for a period of eight hours of work per day and for five days per week.

ELV: Exposure Limit Value, regulated or recommended not to be exceeded as an average value for a period of 15 minutes, and a limited number of times generally between 3 to 5 times for an 8-hour workstation. ppm: part per million part by volume, generally corresponds to cm3 of gaseous substance per m3 of air.

CMR: Carcinogenic substances, Mutagens, toxic for reproduction

APR: Respiratory Protection Device in general except ARI

APRVL: Respiratory Protection Device with Free Ventilation

APRVA: Respiratory Protection Device with Assisted Ventilation

ARI: Insulating Respiratory System

Adsorption or sorption: concerns precisely the phenomena of reversible physical equilibria {adsorption desorption} linked to the trapping of substances on a micro-porous support.

Chemistry Adsorption or chemisorption: Generally involves a first step of sorption of substances, which after having been adsorbed (more or less rapid step), is additionally fixed by an appropriate chemical reaction (more or less slow step). In this case, there is no (or little) reversible equilibrium. Unlike the sorption phenomenon, the chemisorption capacity determined in the standardized tests correctly defines all the uses of such filters, usually called "chemical". In this case, and only in this case, the rule of proportionality between the usage time and the concentration, from of the data indicated in the standards and the actual conditions of use can be applied quite satisfactorily. Absorption: usual generic term improperly applied in the field in respiratory protection which includes the two above-defined phenomena: adsorption and chemisorption

Fig. 1 shows an example of a standardized test result the aim of which is to guarantee, by the manufacturers, protection performance at least equal to the thresholds fixed in standards. These tests are essentially used to determine the times at breakdown concentrations, for a substance or the same group of substances, and the adsorption capacity offered by the filters. In these tests, a constant concentration of substance is continuously sent to the inlet of the filter.

Fig. 2 shows an example of recording the concentrations actually measured on exposure situations typically encountered during packaging operations or loading of substances with breach of confinement, or during maintenance operations on industrial chemical processes, situations generally known to be the most exhibiting. It was recognized by industrial hygienists that a significant portion of average occupational exposures could originate in these short-term exposure situations. This has been completely confirmed in the numerous recordings in real exposure situations made during these tests and affirms the need to be able to have protection adapted to this type of situation.

Fig. 3 gives an example of implementation of the method on the basis of the present invention, carried out with a state of the art APRVA (1) used in a first test phase: an APRVA (1), equipped with a face piece (22) comprising a direct air outlet to the atmosphere, not fitted with valves or flaps (9), has been transformed to receive two separate on-board detectors, one on the intake air (15b) at the inlet of the filter, the other (15a), disposed as a bypass immediately at the outlet (7) of the APRVA (1) on the air at the outlet of the filters (8), supplying, through a pipe (8.1), a cell sample circulation (17) allowing the analysis of the air leaving the filters immediately. This modified APRVA (1) was carried indifferently by different users on several operations deemed to be exhibiting carried out under control, without ever changing the filters (2). Examination of the records (fig. 10) on the intake air (15b) and the discharge air (15a) showed that no trace of substance left the filters (fig. 10), even during very short and very high concentration spikes at the inlet of the filters (several thousand ppm), which validated the effectiveness of the filters used on these strong spikes and allowed us to take the next step. Two separate detectors have been used to eliminate the conventional common mode interference and pollution encountered with a single detector alternately measuring a zero level (filter output) and high concentrations (filter input), as has been proposed in certain prior documents.

Figs. 4a and 4b show two examples among others of the state of the art and of the technique relating to the production of face pieces (visor or mask).

In FIGS. 5 to 9, only the elements having, as a whole, an original character according to the claims, or necessary for understanding the process, are indicated. All the other elements or means or functions necessary for the operation of state-of-the-art APRVAs are known to those skilled in the art and are not indicated or are not detailed in these figures.

FIG. 5 is a diagram of an exemplary implementation of the method of the invention comprising, according to a preferred embodiment, a total return of air by a concentric pipe or by a separate pipe, or, according to a variant, a partial return of air through a concentric pipe, for the purpose of measuring various parameters; an internal continuous circular motion of part of the filtered air for the purpose of carrying out automatic or assisted safety sequences and functions; and using face pieces as shown in figs. 7 and 8 1. an APRVA (1) fitted with filters (2) adapted on their bases comprising an appropriate seal (3.1), an assistance means (5) controlled by a means (19), delivers a flow d air on the outlet of an APRVA (7) towards a face piece (22) by an external concentric pipe (8); 2. such a face piece (22) receives said air delivered at the outlet of the filters (8), delivers it inside said face piece where it is collected laterally (22.4) or on its internal periphery to be returned to such an APRVA, preferably entirely (9) by an internal concentric pipe or separate external pipe before being entirely rejected to the atmosphere (11), or partially (9.2) by an internal concentric pipe connected to a suction means (18) before being completely released to the atmosphere (17). Such a face piece does not include a valve, a valve or a device called "air demand" or "positive pressure";

3. the external concentric pipe (8) of said supplied air derives part of its flow in the pipe (8.1). towards a restriction (16) and the outlet (17), for the purpose of measuring various parameters such as: pressures (12), flow rates (14), concentrations of substances (15), in parallel or independently of the selection means (13) , controlled and processed by a centralized system (19), constituted by a computer system known to those skilled in the art and comprising a microprocessor. The pipe (17) is used to connect an external standard gas for rapid calibration or verification of said detector (15);

4. in a variant with total air return, the internal concentric pipe or the separate external pipe (9) of said total air return opens onto the main pipe (9.3) which derives part of its flow in the pipe (9.1 ) and a restriction (16) towards the outlet (17) for the purpose of measuring various parameters such as: pressure, flow rates, concentration of substances by means of pressure measurement means (12), flow measurement means (14) and means for detecting substances (15), respectively; parallel or independently of the selection means (13) controlled by the centralized system (19);

5. the flow rate values thus measured in the pipes (8.1) and (9.1) allow the respective calculation of the flow rates of said supplied air (8), and of said total air return (9) by the centralized system (19) from flow ratio coefficients [(8) / (8.1)] and [(9) / (9.1)], calibrated during construction on the restriction (16) located in the outlet pipe (17) or on such a pipe acting as a restriction or on the flow measurement means (14) acting as a restriction, coefficients stored on the centralized system (19); in a variant with partial air return, the internal concentric pipe (9.2) of said partial air return is connected to a ventilation means (18) to a restriction (16), for the purpose of measuring various parameters such as: pressures (12), concentrations of substances (15), measurement of flow rates (14). In this variant, the pressure (12) available in the facepiece is measured when the centralized system (19) controls the selection means (13) which connects the pipe (8.1) to its outlet and simultaneously stops the ventilation (18) and conversely, to be able to use the flow measurement in the pipe (8.1); the concentration of substances (15) is measured when the centralized system (19) controls the selection means (13) which connects the pipe (9.2) to its outlet and simultaneously starts ventilation (18), in this position measuring the flow (14) is only used to check the presence of a flow during the measurement of concentration of substances; in such a variant certain functions or determinations cannot be carried out: the regulation of the positive pressure (10) in such a face piece, the determination of the air demand of a wearer, the total leakage to the outside of such a face piece, said main pipe (9.3) of said total air return (9) is connected to a means of control and regulation (10) of the positive pressure in said face piece, controlled by the centralized system (19 ) from the actual pressure measurement available in said face piece (12a) (12b) and / or from the differential pressure between the pressure at the outlet of the assistance means (5) and that available inside such a face piece (12b); such an air return exhausted to the outside by a connection means (11), can be captured for controlled ventilation of an over-protection of the hood type or combination fitted to a carrier. 8. the assistance means (5) of said supplied air establishes a continuous continuous circle by the line (6) of a low air flow equally distributed on either side of the selection and isolation means confirmed filters (4), used in controlled sequences of automatic safety by the centralized system (19) in which they are integrated. Such a low air flow makes it possible, after selection of a filter by the means (4) and its confirmed isolation, to maintain a slight overpressure between said selection and isolation means (4) and the mechanical shutter valve (3.10 ) arranged on the same filter. This provision is reinforced by a slight leakage rate voluntarily created through said mechanical shutter valve, guaranteeing the non-return of substance on said selection and isolation means (4) whose tightness can never be 100% guaranteed;

9. A means of information and alarm of resonator / vibrator type very low non-audible frequencies (20), having sufficient autonomy, is controlled by the centralized system (9) and vibrates the air column (8 ) in communication with the interior of said face piece (22), so that these vibrations are directly perceptible on the face of a user; such a means can be constituted by an external vibrator (20.2) placed as close as possible to the contact of the skin of a wearer and receiving such vibrations. Both variants do not involve the senses of sight and hearing. the information is formatted and limited to be useful for maintaining the protection of a holder and for the simple actions requested of him for this purpose. The modulation of the delivered vibrations is additionally and locally displayed (20.1) in the same format in the form of a timing diagram reproducing the modulation of such information or alarm vibrations. Some examples of activation of such an information method are summarized below.

10. An information storage means comprising a memory area (21) in which the centralized system (19) records directly in real time any information or useful data usable in real time or deferred for the mastery and control of such a process or device. Such a means comprising a memory area is known in the art and can be for example: a remote transmission or a manual or automatic reading by means of a contactless reading method, of the RF-ID type for example, for transferring such information or data on a computer program for operational purposes.

Figures 6, 7 & 9a, 9b show an example of application of the method and preferred embodiment of such an APRVA, in a variant with total air return produced by an internal concentric pipe, usable with a preferred embodiment of such a face piece carrying out such a total or partial air return in such a concentric pipe, and their operating principle. More specifically, these figures show: a) an APRVA (1) fitted with filters (2) adapted on their bases comprising an appropriate seal (3.1), and a fan (5) whose operation is regulated and controlled by a system centralized known in the art (19), delivers an air flow on the outlet of the filters (7) to a face piece (22) by an external concentric pipe (8). b) a face piece (22) detailed in FIG. 7, provided with a very flexible facial seal (22.1) and with a sealed adjoining screen (22.2), is produced so as to receive said air supplied at the outlet of the filters (8) and to distribute it inside said face piece by orifices arranged for this purpose (22.3). The rigid or semi-rigid part of said face piece (22.0), forming a shell, collects laterally or peripherally (22.4) inside such a face piece all of the air preferably to direct it towards an outlet internal concentric (9) constituting said total air return. Such a face piece does not include a valve, valves or a device called "air demand" or "positive pressure". c) the external concentric pipe (8) of said supplied air comprises a connection with the pipe (8.1) to the pipe (17) and the detector (15). d) the internal concentric pipe constituting said total air return (9), protected from any external pollution, is returned to said APRVA on a main pipe (9.3) comprising a connection with the pipe (9.1) to the pipe (17) and the detector (15). e) a means of selection (13) of said total return of air (9.1) or of said supplied air (8.1) to the pipe (17) and the detector (15), is controlled by the centralized system (19) to which said selection is incorporated. f) the conduits (9.1) and (8.1) of said selection comprise static communications with means for measuring differential pressures, processed in parallel or independently of said selection by the centralized system (19): fi), the means (12a) measures the pressure of said supplied air established differently from atmospheric pressure advantageously transmitted through a sealed and deformable buffer capacity (12c). fii). the means (12 b) measures the pressure of said total return of air with respect to the pressure of said supplied air, allowing the evaluation of the real pressure available in said face piece, when the pipe (8.1) is selected (13) towards the pipe (17). The introduction of a restriction (16) in the outlet pipe (17), or such a pipe acting as a restriction or the flow measurement means (14) acting as a restriction, makes it possible to maintain in such a pipe ( 8.1) the actual pressure available in such a face piece independently of the selection (13), therefore the continuous measurement of the differential pressure between said supplied air (8), (8.1) and said total air return (9), (9.1), without being obliged to use a third measurement referring to atmospheric pressure (12a) (12c). g) said substance detector (15) is arranged in a compartment accessible from the outside (15.2) allowing, without dismantling said APRVA, the easy replacement of the type of measuring cell used (15.1) on said detector, which is managed by the centralized system (19) in the operation of which it is completely incorporated. The addition of a restriction (16) in the outlet pipe (17), or the use of such a pipe acting as a restriction or the flow measurement means (14) acting as a restriction, also allows the maintaining a positive pressure on the measuring cell (15), avoiding any external pollution. h) the main pipe of said air return (9.3) is connected to a means for controlling and regulating (10) the positive pressure in said face piece (22), means comprising at least: a diaphragm / shutter valve (10.1 ), a spring (10.2) exerting a low pressure on said diaphragm / valve, means (10.3) for adjusting the tension exerted by said spring on said diaphragm / valve controlled by the centralized system (19) from the measurement of actual pressure available in said face piece (12a) (12b) and / or the differential pressure between the pressure at the outlet of the filters and that available inside such a face piece (12b). i) the pipe (17) comprises a flow measurement means (14), processed by the centralized system (19), controlling the presence of an air flow in the pipes (8.1) or (9.1), supplying said substance detector (15). The flow values thus measured in the pipes (8.1) and (9.1) allow the respective calculation of the flows of said supplied air (8), and said return air (9) by the centralized system (19), from the coefficients reporting of flow rates [(8) / (8.1)] and [(9) / (9.1)], calibrated during construction on the restriction (16) in the outlet pipe (17) or on such a pipe acting as restriction or on the measuring means (14) acting as restriction, coefficients stored on the centralized system (19). j) the line (17) is also used to connect an external standard gas for rapid calibration or verification of said detector (15), without any dismantling and in any position of said selection means (13), as soon as such an APRVA is in normal operation. k) the external part (8) of said supplied air comprises a connection with the pipe (6) establishing a permanent and continuous circle motion with a low air flow rate equally distributed on either side of the filter selection means (4) controlled in automatic safety sequences by the centralized system (19) in which they are integrated. Such a low air flow allows after: selection of a filter by means (4), closing of the corresponding shutter on the other filter and confirmation of this closure by a contact established in the closed position between said shutter and a contact point arranged in the pipe, to maintain a slight overpressure between said shutter shutter and the mechanical shutter valve (3) (3.10) disposed on the same filter. Such safety is reinforced by a slight leakage rate voluntarily created through said mechanical shutter valve, guaranteeing the non-return of substance on said shutter shutter, the tightness of which can never be guaranteed at 100%, in particular in operations comprising removing a filter or replacing such a seal (3.1) in operation.

I) the part (3) detailed in fig. 9a, includes a tightness sensor and tightening force limiter joint (3.1), performing the following functions: first, sealing performed on both sides on the parts (3.1a) and (3.1b); secondly, limiting the compression compression of the seal (3.1) by deformation of the resilient internal part (3.3), with perception of the end of manual tightening by mechanical stop between the two discs (3.2) through the internal contact points (3.4); third and simultaneously, detection of the end of tightening and of the normal presence of the filter on its base by closing under a controlled atmosphere of an electrical circuit established between the two discs (3.2) through the internal contact points (3.4) , after the compression phase of such a seal; a suitable device makes it possible to hold such a seal in position: for example the plug (3.7a) allows the holding in place of such a seal, by being pressed on its base integrally fixed in the pipe (3.6a), additionally connected to an electrical circuit through a sealed wall passage (3.8); in this example, the plug (3.7b) is inserted in a floating manner on a connector (3.6b) connected to a flexible extensible wire itself connected to an electrical circuit through a sealed pass-wall (3.8). Such a seal is easily removed and replaced from the outside using, for example, an extractor (3.5) fixed to one of the discs (3.2). m) the part (3) also comprises, on the outlet of the filters, a conventional mechanical shutter valve (3.10) consisting of two flaps (3.11), free to rotate on an axis (3.12), under closing tension by a spring (3.13). Such a valve is fixed inside the pipe on clips (3.14) and realizes the closing of such a pipe on the internal ring (3.15). such a valve is necessary in the controlled sequences of automatic safety and contributes to the maintenance of protection in the event of failure of the respiratory assistance means (5) (1). Such a valve is easily replaceable by an access means (3.9) without dismantling such an APRVA.

Such APRVA and face piece embodiments, in all cases allow variants, with total or partial air return: • to alternately measure the air quality at the outlet of a filter (8) and the air quality at the outlet of a face piece (9), at a programmed frequency adapted to the service of such an APRVA and to the response time of the type of cell used (15.1) which is generally between a few seconds and a minute on such a detector (15), thus continuously determining the real protection offered to a user, • a more secure use of this type of protection by a method of double differential analyzes on the centralized system (19) to which these methods are incorporated: - the first analysis is carried out between a zero measurement carried out on the air at the outlet of the filters, recorded at the commissioning of such APRVA, and the evolution of this measurement, in absolute value and / or drifting per unit time, during the use of such APRVAs, - the second analysis is carried out between the air on the outlet of the filters and the air returning such facepieces, on such APRVAs. • a lockout ordered on a single filter, or the remaining filters, with protection maintained, in the event of a fault specifically observed on a filter and / or such a filter seal. • the use of a simple means of information and instruction passing of the resonator / vibrator type at very low frequencies (20), not audible, supplied by an autonomous buffer battery, controlled by the centralized system (19) and vibrating the air column in communication with the interior of said face piece, so that this vibration is directly perceptible on the face of a user or directly transmitting these vibrations to a vibrator closest to the contact of the skin of a wearer (20.2), without soliciting the senses of sight or hearing. This means advantageously solves the problems of a hearing or visual handicap, or linked to sound environments. Said face piece does not comprise any mechanical or electromechanical or electronic organ. The information method is voluntarily limited for the bearer to the content useful for maintaining their protection and to the simple actions requested of them for this purpose. Such a method would be better understood through a detailed functional and schematic description of some examples of its activation, examples not developed in the invention. However, in a general and nonlimiting manner, such a method uses a very low fixed frequency modulated in an appropriate manner necessarily comprising several levels of modulations, for example extreme: - the absence of vibration would indicate normal operation and guaranteed protection; vibrations at a fixed frequency with more or less long and symmetrical, continuous or discontinuous modulations would indicate degraded operation remaining under control or the detection and localization of faults that a wearer can immediately correct; - vibrations at a fixed, unmodulated and continuous frequency would indicate to the wearer that his protection under conditions of sufficient security is no longer ensured, that he must press said face piece on his face and imperatively leave the risk zone without haste or haste;

This information specific to a protection defect is additionally displayed on a general display means (20.1), incorporated into the centralized system (19), for any other person carrying out close surveillance or providing assistance and rescue to a carrier in difficulty. Such a display is advantageously produced in the form of a chronogram modulated in the same way as on the resonator or the vibrator. This information can also be recorded in a synthesized form in the memory zone (21) of an information storage means, for any useful use in real time or later or deferred after reading of such a memory by an appropriate means. • However, as described above, any variant with partial air return does not allow the determination of a wearer's air demand, the determination of the leakage to the outside of such a face piece, the regulation of positive pressure in such a face piece. The control system (19) will only act, within a certain programmed limit, on the speed of rotation or the power delivered to the main fan (5) to try to best maintain a pressure set point inside such a room. facial, this in combination with the information of the flow calculated on said air delivered at the outlet of the filters (8). The combination of these different factors, combined with a substance detection, still allows a relatively safe operation of such an APRVA, but with the classic drawback of a reduction in the duration of use of the filters necessarily linked to the increase in air flow, said duration of use of the filters still being controlled in this case on such an APRVA comprising means for measuring substances. On the other hand, the air flow returning from such a face piece to such an APRVA for the measurement or control of various parameters, in particular the concentration of substance, could only be guaranteed by the addition of a fan. annex (18) thus creating a risk of depression in the pipe (9.2) supplying the detector (15), therefore a risk of pollution by the outside environment.

Such examples of APRVA and facial pieces, in all cases allow variants with total concentric or separate air return: • to determine differentially on said air return, the instantaneous air demand and / or mean of a carrier, measured as being proportional to the extreme or average flows noted between the inspiration and expiration phases, • to determine differentially between the average flow rates of said total return of air and of said delivered air, the total air leakage towards the outside of such a face piece. • to resolve the classic difficulty encountered in the event of a power failure with such APRVA using such face pieces by adopting a control logic: - default position: Normally Closed from the two shutters towards the outlet (17), on the selection means (13) thus preventing any return of substance via this outlet; - default position: Normally Open the shutter at the outlet of the filters, common to the two filters in a preferred embodiment described, on the selection means (4), thus allowing normal use of the filters without ventilation;

These provisions are supplemented by the presence of mechanical leakage shutter valves with limited leakage (3.10.) On the air assistance inlet. Such a limited leak, necessary for the automatic safety functions, occurs towards the outside on the filtered air side and does not pose any problem in this case since the flow of such a leak in the expiratory phase represents only a few% of the flow. expiratory, thus avoiding an accumulation of carbon dioxide inside the assembly composed by such an APRVA plus such a face piece. Sufficient respiratory protection is thus maintained and makes it possible to leave a risk zone without precipitation or to be rescued on site by a third party.

Fig. 10 shows examples of results, on another phase of tests, of the process on which the present invention is based: an APRVA [FIG. 3 (1)] state of the art voluntarily unprocessed and equipped with two filters and a face shield (22) of the state of the art has been worn indifferently by different users, on all situations or operations exposing to the substance tested. Measurements were regularly performed on the air leaving the filters. The filters remained voluntarily on the APRVA and out of any pollution, without obturation or treatment, to take into account the phenomena of internal migration of the substance in the filter. Several sets of filters have been tested in this way. They gave the same cumulative usage time under comparable conditions of use, before the appearance of the substance on exit. These records show that the growth of this output concentration is slow enough to allow its detection under good security conditions with APRVA and face pieces as shown in the present invention through the embodiments and variant, preferred or not.

Fig. 11 shows an example of cross-checking of the results obtained under real conditions shown in FIG. 10, by a method of simulating exposure situations comparable to the same substance, carried out on a test bench (30) by injection of pure substance, on an identical filter in order to verify the behavior of the substance on such a filter and the potential consequences of high concentration peaks or exceeding the duration of use determined previously. The results of the tests carried out on a bench (fig. 14) confirmed several points concerning the adsorption equilibria, very interesting points when they are applied to the control of these filters under real conditions of use and to the analysis of their operation: - the substance came out completely from the filters if the scanning was continued with air, wet or dry, co-current with the direction of normal use - the substance came out even faster if this scanning was done after each use and against the direction of normal use. - the filters after total desorption of the substance, regardless of the direction of desorption, regain their characteristics and could be reused a large number of times with the same performance. - the cumulative usage time previously determined (fig. 10) should be interpreted as being related to the time of exit or resolution of the substance on the filters. - the exit time can be considered as a constant, for a given substance, on a given support and under given resolution conditions (t °, pressure, gas flow rate, etc.). - we will distinguish the exit time (beginning of appearance of the substance) from the resolution time (maximum of the resolution peak). The release time, to a certain extent, varies little depending on the quantity of absorbed substance on the filter as shown in fig. 14. This will be all the more verified as the concentration of substance will be low in the air drawn in on a filter.

The rate of increase of the concentration of substance at the outlet of the filter is generally sufficiently slow to allow a direct and reliable measurement of a concentration threshold not to be exceeded, with APRVA and face pieces as shown in the present invention through the embodiments and variant, preferred or not. the maximum concentration measured at the outlet of the filters is much lower than the maximum peak values measured at the inlet. The ratio of concentrations: exit / entry decreases rapidly in relation to the increase in the exit or resolution time of the substances. This phenomenon is due to the equilibria and to the fact that the adsorption filters also behave like real "capacitive attenuators and integrators". This behavior will be all the more verified as they will be substances with high boiling points and / or that the filters will be used far below their limit of adsorption capacity. the extrapolation of this capacitive behavior makes it possible to affirm that if the filters were never replaced (hypothetical situation), or were too late (situation which must certainly be encountered in the state of the art), the concentration average output from the filters will tend towards the average of the concentrations integrated on the filters and usually encountered or measured on the corresponding exposure situations. the peaks of exposure encountered in such exposure situations will never be inhaled by a protected user, even in the absence of rigorous management of the filters; it would inhale at most, during the period of wearing the protection, the average of the concentrations of the substances incorporated on the filters and usually encountered on the exposure situations concerned, however, the important point to remember is that this will always result in a significant lowering of the exposure value average professional over 8 hours (see VME) and especially over 15 minutes (see VLE). This reduction will be all the more important as the duration of the port will be short and the time of exit of the substance on the filters greater.

This interpretation of the actual behavior of the filters corresponds on average to the way they are used in the majority of state-of-the-art cases, this in the absence of strict control or single use, although single use does not guarantee that the exit time previously determined will not be exceeded, depending on the duration of the single use and the exit time of the substance encountered. We can better understand the safety margins adopted by suppliers on the use of adsorption filters, especially in the case of substances with low boiling point which are precisely those where the exit times will be the lowest, and the tendency current not to recommend the use of such filters on so-called CMR substances, for example carcinogens. In conclusion, knowing the exit time of a substance on an adsorption filter, operating in a range far from its saturation and / or its capacity limit, used continuously under realistic exposure conditions, makes it possible to control the period during which such a filter will be effective for all of its comparable applications in respiratory protection.

Examination of an example of substances tested by the process on which the present invention is based (FIG. 3) on filters of the AX type illustrates these points. The substance is classified in the ^1st group, with an TWA less than or equal to 10 ppm, for a usage time of 50 minutes in free ventilation indicated in standard EN 371. The time indicated in the instructions for the AX filter supplied by the manufacturer takes 20 to 40 minutes, also for use in free ventilation. The effective use time effectively measured in assisted ventilation at a constant flow rate of 60 1 / minute, for an average concentration measured over the duration of the situations actually tested (fig. 2) comparable to the VME of 10 ppm given in the standard, is about 250 to 300 minutes before start of appearance of the substance at the outlet of the filters (fig. 10). This time is 5 to 10 times greater than that indicated in the standards or the manufacturer's instructions. A priori evaluation of the duration of use, as recommended in various guides or instructions for use, from the data of the standardized tests and by interpolation of the two variables: concentration and breakdown time, interpolation based solely on the notion of capacity taken as a reference would have indicated for the conditions actually tested (fig. 2) a time between 1000 and 2500 minutes. This time has no real meaning since the duration of use of this filter is in principle "self limited" by the recommendation of single use by the supplier, which would make a maximum of 480 minutes which is the usual duration of a day of work. This is not certain, however, because the same user, more or less specialist, could logically enough consider on the basis of this time of 1000 or 2500 minutes, that it would be possible for him to reuse at least once, if not several times the same filter (economical and easy to use). Anyway, and this has been demonstrated by the examples of tests carried out under the conditions of use, by the process on which the present invention is based: - from approximately 250 to 300 minutes of continuous use the user would have inhaled the substance; - from approximately 400 to 600 minutes of continuous use it would inhale the average concentration of the substance encountered on protected exposure situations; on the other hand, this has been demonstrated in reality and under the same conditions on a bench (30), it would never inhale the peak concentrations encountered on these same exposure situations

We note, on this single example, the difference between the times extrapolated from the test conditions of the standards, the indications of the suppliers in their instructions and the real data observed by a prescriber, (cf .: fig. 10 & 14) concerned to provide its staff with operational, effective, controlled and effectively used protection. It is certain that all filters using only active carbon as an adsorbent (A2, A1, etc.) work, and work poorly, depending on the same mode, including on substances with higher boiling point, but in this case at a less perceptible level. This analysis of the functioning of the filters is optimistic, because it does not take into account the phenomena of diffusion or migration of substances inside the filters, when they are used several times, during the storage periods between each use, phenomena which further deteriorate the conditions for the safe use of these filters. However, these results do not make it possible to extrapolate the factor 5 to 10 of this example to other substances which may have a different dynamic behavior on this type of filters. Nor is it realistic for a prescriber to want to test all the substances and applications possible in real situations, as we have done in the various tests with the process on which the present invention is based (fig. 3) or , a fortiori, according to other more complex devices described in certain inventions, Such a procedure, however effective, would be too cumbersome to implement and would have no lasting operational character. Only a method like that described in the present invention implemented on APRVAs equipped with face pieces as shown in the present invention through the exemplary embodiments and variant, preferred or not, could exempt a prescriber from the prior evaluation. conditions for the use of such filters, while guaranteeing safe use. However, this preliminary assessment is feasible, in the absence of the use of such APRVAs or in addition in general, on a test bench (30), by a method of simulating situations of real extreme and average exposures, with study of the mode of operation, of the malfunction of such filters and of its consequences, such as the teachings of the process on which the present invention is based and the examples of tests described in FIGS. 3 & 10 show it. Fig. 12 shows an example of back sweeping of the tested substance carried out on a filter after actual use. This back-scanning was carried out on a bench (30), in order to verify the reversibility of the adsorption equilibria in real situations. The same result is obtained on a test bench (30), an example of which is described in FIG. 13, by a method of simulating situations of comparable exposures implemented on such a bench and described below. Fig. 13 shows a preferred embodiment of a test bench (30) of such filters, created for this purpose in the laboratory for a phase of complementary cross-checking tests on the same substance injected in the pure state, more generally, on n any other substance (s) injected in a pure state or in the form of mixtures, with any type of protective device used, provided that the air flow during the tests is comparable to the average flow rate of the protection that will be used. Such a bench comprises at least one or more of the following devices: - an air drying installation (not shown in fig. 13) - an air flow control device (31), adjusted according to the flow conditions means in actual use of the filters - an example of an air humidification device (32) comprising a water capacity, agitated by an appropriate means (37) and heated by an appropriate means (38) to recreate by continuous vaporization, if necessary, humidity conditions comparable to those encountered in real exposure situations. This humidifier allows you to test by comparison, and all other things being equal, the effect of this humidity on the efficiency of the filters used. - A buffer capacity (34) of known suitable volume and agitated by an appropriate means (37), for example about 30 liters corresponding to the volume of air inhaled for about one minute by a person making a normal effort. A recording detector can be introduced or connected to it (36) for instantaneous concentration measurements at the inlet of the filter. - devices for introducing (33) known quantities of pure, gaseous or liquid substances, separately or in the form of mixtures, into such a capacity and a bypass system (33.1). - an airlock (35) allowing the filter to be tested to be connected to the capacity in the direction of normal use (35.1) or in the direction of back-sweeping (35.2). - a device for connecting a recording detector (36) after the filter. This prior evaluation is carried out according to a preferred method based on the experience resulting from the process on which the present invention is based. In the privileged example described, such a method is suitable for reproducing at least the extreme and average phases of the real conditions observed and measured in the field. This method takes into account a recommended time limit, approximately one hour is generally accepted as ideal, for the continuous wearing of respiratory protection, this time can be increased to two hours under particularly satisfactory ergonomic conditions. At the end of this period, a rest period must generally be observed, during which the filters can be replaced if necessary or checked. This method directly uses pure substances separately or in the form of mixtures This method introduces safety factors on several aspects, as well as the systematic verification of the reversibility of the adsorption to validate the possibility of treatment outside the periods use. This method is generalizable to all types of filters and to respiratory protection in free ventilation, such a method comprises at least one or more of the following phases: 1) Simulated maximum concentration: it is at least greater than a certain number of times, for example 10 times, the highest peak value recorded, generally for a short time, in an actual work situation, 2) Number of simulated maximum concentration phases: it is set according to the nature of the exposures observed in the field , for example five or six phases of injections over a given period, for example an hour, cover the majority of situations encountered in Industrial Hygiene, the first when the test is started, followed for example by four or five others at more or less regular intervals, 3) Simulated average concentration: the simulated maximum concentration phases are fixed, for example on ladi the given period, so as to give an equivalent average concentration at least equal to a certain number of times, for example 20 times, the value of the actual average professional exposure measured over said given period, 4) Minimum average concentration to be simulated: if a measured actual Average Occupational Exposure Value is lower than a certain number of times, for example 20 times, a Limit Value of the substance tested for a given time, the phases of maximum concentrations will be fixed on said given period, according to such a Limit Value, so as to be at least equivalent on average to a certain number of times such a Limit Value, without ever exceeding the total theoretical capacity available of a filter ,

5) Total duration of the simulation test: it is continued after the phases of maximum simulated concentrations, for example over said given period, and phases 2), 3) or 4), until the appearance of the substance leaving the filter measured as the exit time and / or until recording of the maximum of the concentration peak measured as the time of resolution of the substance on the filter,

6) Verification of the reversibility of the adsorption: steps 2), 3) or 4), as the case may be, are repeated on a new or regenerated filter, so as to simulate the progress of an operation over said given period. The air flow is maintained for some time, for example ten to fifteen minutes, after the last injection phase. The filter is then placed in the back-sweeping position on the bench and a flow of an appropriate gaseous fluid is maintained, until the total purging of the filter substance: o the purge end time represents in these conditions the time during which an adsorption filter should be treated by back sweeping under the same conditions to be regenerated and that there is no longer any substance inside, o to control such a back sweep the quantity of substances found, must be comparable to the quantity of substance introduced,

7) The maximum authorized continuous use duration: it is equal to said exit time from the substance noted in 5), apart from any other provision of actual measurement of this duration, The results of these tests are used to determine the conditions of use of the adsorption filters, in real exposure situations, in particular:

8) The recommended cumulative duration of use: this is the time 7), divided by a safety factor which must take into account the maximum authorized availability period 9), apart from any other regeneration treatment provision or special such filters,

9) The maximum authorized availability period: period after which a filter must be replaced whether or not it has been used, whether in the case of an individual allocation or in the case of use collective, apart from any other regeneration or special treatment provision for such filters. Fig. 14 shows examples of resolution curves of the tested substance, produced on a test bench as shown in the example of FIG. 13, in simulated exposure situations by the method described above, at average concentration levels between 2 times and 20 times the VME of the substance corresponding over the duration of the test to 10 to 100 times the ELV of such a substance , that this ELV exists legally or that it is considered in relation to rules of use. These curves confirm that the exit time of a substance, at a constant flow rate value corresponding to real average conditions, is comparable to a constant largely independent of the average concentration injected, at least for the concentration values usually measured in Industrial Hygiene . The results obtained on such filters and such a test bench by such a method completely overlap with those established in real exposure situations, in particular as regards the determination of the exit times of the substances. Figure 15 shows an example of a humidity and temperature variation curve quickly measured at the outlet of a filter when a significant quantity of substances is more or less abruptly adsorbed at the inlet of the filter, producing a sort of image "mirror effect" of the quantity of substances adsorbed at the inlet of a filter, this long before said substance is detectable at the outlet of a filter. In a large number of cases, this variation in humidity at the outlet of the filters is a normal component of their functioning which can cause a wide variety of substance detectors, such as that used in the invention US 6162281, to fail, or else for example if a PID (Photo Ionization Detector) is used. The measurement and knowledge in the proposed invention of said humidity and temperature allows in a large number of cases to correct by appropriate phenomenological laws the interference of said humidity and / or temperature on some of said measuring means, for example PIDs. FIG. 16 shows, in a described example dealing with adsorption of different substances at variable concentration levels, the phenomenological relationship between the molar fractions of said different substances injected on different filters but whose humidity conditions are controlled, and the molar fraction of water displaced according to said "mirror effect" shown in FIG. 15. Variable molar fractions of vinyl chloride (CVM), methylene chloride (CM2), chloroform (CM3), carbon tetrachloride (CM4) ), 1, 2-dichloroethane (DCE), butadiene (C4 ==) were injected onto said test bench and according to said method described previously in FIG. 13. The initial water content at the outlet of the filters when they are put in service under the conditions of the tests carried out remained under control and between 14,000 and 17,000 ppm

The undifferentiated treatment of all the results obtained on several different tests and filters shows that the said phenomenological relationship: variation of the water concentration and the t ° at the outlet of the filters as a function of the molar fraction of an injected substance, what that is the injected substance as soon as the thermodynamic phenomenon involved (a sorption, or a chemisorption) is a linear function perfectly correlated. Such a linear function makes it possible, by simply measuring the relative humidity (water vapor concentration and t °) at the outlet of the filters, to predict and anticipate any abnormal or degraded operating condition which would dangerously reduce the capacity remaining available on a filter. , this long before the substances which are at the origin of them are detected at the output of such filters operating under controlled humidity conditions.

The same phenomenological relationship is demonstrated with the measurement of the temperature at the filter outlet, with the same objective of anticipating abnormal or degraded filter operating conditions, whether the thermodynamic phenomenon involved is a sorption or a chemisorption, with however differences in temperature corresponding to the differences in energies of the two phenomena, generally of an order of magnitude.

Claims

1. Method of respiratory protection with assisted ventilation, characterized in that one collects laterally or peripherally inside a face piece made for this purpose all, preferably, the air which is sent there by a respiratory assistance system filtering said air, that all of said collected air is returned to reject it entirely to the atmosphere remotely at said respiratory assistance system; said air collected inside such a face piece is channeled to an appropriate pipe, preferably concentric and internal to that of delivery of said sent air, returned in full until said respiratory assistance system and said return is used. total air for the measurement or control of one or more operating parameters of said process and of said respiratory system by the implementation of operations or means appropriate to the measurements or controls operated with the objective of actually controlling: the effectiveness and the duration of use of the filters, the tightness of such a face piece, the safe operation of such a respiratory assistance method.

2. A method of respiratory protection with assisted ventilation, according to claim 1, characterized in that in a variant said return of the air collected laterally or at the inner periphery in a face piece is produced so that it constitutes a return partial to said respiratory assistance system.

3. A method of respiratory protection with assisted ventilation, characterized in that a circle is made continuously of part of said filtered air as close as possible to the delivery and suction points of said respiratory assistance system and use is made such goes in circles in controlled sequences of safety functions or assisted replacement of filter or seal, without losing the benefit of protection.

4. A method of respiratory protection with assisted ventilation, according to one of claims 1 to 3, characterized in that it is designed in such a way that it performs one or more of the following steps: a) selection of the air delivered at the outlet of the filters to such a face piece or from said air return, total or partial, of said face piece, for the purpose of measurements or functional check on different parameters; b) measurement, parallel to or independently of said selection, of the air pressure on said air returns, total or partial, with respect to the pressure of the air delivered or relatively to atmospheric pressure, and, parallel to said selection, of the flow rate on said total air return with respect to the flow rate of said supplied air; c) control and adjustment of the actual positive pressure available in said face piece, by acting on said respiratory assistance system on said total return of air; d) differential measurement, in the case of said total air return and on said total air return, of the instantaneous and / or average air demand of a carrier; e) differential calculation between said total return of air and said delivered air, of the total leakage rate of air to the atmosphere of said face piece; f) control and adjustment of the flow rate of said air delivered by said respiratory assistance system so as to maintain a flow rate at least equal to the sum: [wearer's air demand + average air leakage to the outside + a value additional fixed or advantageously proportional to said air demand from the wearer]; g) differential measurement of the substances leaving the filters on said air delivered between an initial state observed when they are put into service and the evolution of these concentrations during actual use, in absolute and / or derived value, determining their effectiveness instantaneous and their duration of use limit; said substances comprising the relative humidity of the air, said relative humidity including a temperature measurement; said humidity and / or temperature being used on the one hand as an "instant mirror image" of the quantities of said substances adsorbed at the inlet of the filters which would significantly or dangerously affect their efficiency, and on the other hand to correct by appropriate laws l interference of said humidity and / or temperature on some of said measuring means, for example PIDs. h) alternative measurement, by means of said selection, of the concentrations of substances in said air returns, total or partial, and said delivered air; i) differential calculation of the leakage in substance towards the interior of said face piece, therefore of the actual exposure to the substances with the wearing of a protection, independently and in addition to the concentration of breakdown of substances measured on said delivered air, and controlling this leak by acting on said respiratory assistance means; j) carrying out a continuous and constant circle rotation of part of the filtered air between the suction and the delivery of said respiratory assistance means, for example a ventilator, for the purpose of carrying out controlled sequences of operation in safety of said respiratory assistance system; k) active verification or control, for example by means of a seal specially made for this purpose: of the seal produced between a filter and its support, of the tightening pressure exerted on such a seal, of the manual perception of the end normal tightening of a filter on its support, the normal presence of a filter on its support, through such a seal;

I) maintaining sufficient protection on a single filter or on the remaining filters, after detection and isolation of a filter and / or such a worn or defective seal in the event of degraded operation of said assistance system involving games at least two filters and using said controlled sequences; m) informing a wearer without being interfered with by his environment and without signaling him in his environment by the sole use of very low frequencies that are not audible; n) informing a holder of the only faults relating to the maintenance of his protection with a simple and assisted action request to keep or restore this protection, supplemented for example by a local display and / or the recording of such information; o) optional and assisted replacement of (or) filter (s) and / or (or) such (s) filter (s) in emergency situation, while retaining the benefit of protection using said commanded sequences; p) maintaining sufficient protection, in said case of said total return of air, in the event of failure of said respiratory assistance system, for example the ventilator, using such a face piece not equipped with valve, valve or other so-called devices air demand; q) supplement respiratory protection with skin overprotection using such a total return of air normally put into the atmosphere in its entirety by capturing it at the outlet of such a respiratory assistance system and by occasionally and locally adapting it to said part facial such over-protection of the access or transfer airlock type, for example for drinking, eating, providing care, etc., or more completely a hood or a ventilated suit, establishing the controlled ventilation of such over-protection by such an APRVA; r) cross-checking the determination of the real efficiency of the filters as demonstrated in step g, by a method of simulating situations of extreme and average exposures, carried out on a bench; such a method taking into account the effect of humidity can be generalized to respiratory protection without respiratory assistance.

5. Method according to claim 4, characterized in that step b) is advantageously carried out in parallel with step a) which alternately selects, in a coupled manner for this step, and in derivation a part of the air flows: of said supplied air, at the same time as it closes the opening of said total return air, allowing a measurement of flow rate on the bypass of said delivered air and a measurement of the pressure on said total return air in pressure equilibrium with the interior of said face piece, in relative value with respect to atmospheric pressure, or in differential value with respect to pressure of said supplied air, or, • of said total return of air, at the same time as it closes the opening of said supplied air, allowing a measurement of flow rate on the bypass of said total return of air and a measurement of the pressure on said supplied air in pressure equilibrium with the output of an assistance means, in relative value by r contribution to atmospheric pressure, or as a differential value with respect to the pressure of said total air return, with respective calculation of the flow rates of said total air return and of said air supplied from the coefficients of the flow rate reports calibrated and stored at the construction between the flows measured on the main flows and such diversions.

6. Method according to claim 4 characterized in that step c) consists in regulating the actual pressure inside said face piece to a programmed set value, from the measurement of the pressure carried out in step b): in absolute value measured on said total air return, or in differential value between said total air return and said delivered air, by increasing or decreasing the tension exerted by a spring on a diaphragm / valve disposed on said return total air before it is fully vented. Such a spring is mechanically held in a known fixed position, by default of current or control.

7. Method according to claim 4 characterized in that step d) consists in differentially determining on said total air return the instantaneous and / or average air demand of a carrier, measured as being proportional to the difference extreme or average flow rates recorded between the inspiration and expiration phases, for example half in said case of the average air demand of a wearer.

8. Method according to claim 4, characterized in that step e) consists in differentially comparing the averages of the flow measurements of said total return of air and of said air to determine in particular the total leakage of air to the outside. of such a face piece.

9. - Method according to claim 4, characterized in that step f) consists in acting on at least one of the parameters controlling the power of said respiratory assistance system to obtain a flow rate on said delivered air at least equal to the sum flow rates: [of said average air demand of the wearer + of said average air leak to the outside + a complementary, fixed or advantageously proportional value to said average air demand of the wearer].

10. Method according to claim 4, characterized in that step g) consists in using in such a method and integrating into said respiratory assistance means suitable interchangeable detectors of said substances, said substances including relative humidity, and incorporate into functioning said detectors measuring the concentration of said substances on said air at the outlet of the filters an optional reset of the measurements, programmable and triggered at a configurable time after the start of said respiratory assistance means or optionally after each replacement of the new filters or verified, and to apply a differential measurement method, in absolute value and / or in drift per unit of time, between an initial state observed corresponding to the said zero measurement carried out and any state likely to occur later during the uses of such filters, to control their instantaneous effectiveness and / or the limit of duration of use.

11. Method according to claim 9, characterized in that step h) consists in measuring by means of a same detector of said substances, alternatively, the concentration of said substances on said air return, total or partial, at the outlet of said face piece and the concentration of said substances on said delivered air.

12. Method according to claim 4, characterized in that step i) consists in calculating the difference in concentration of said substances between said air return, total or partial, and said delivered air, independently and in addition to the concentration of breakdown of said substances measured on said delivered air, and to control the leakage of said substances towards the interior of such a face piece with respect to a programmed threshold, by acting at the level of said respiratory assistance means on regulating the pressure and / or of the flow in the case of said total return of air, or on the only regulation of flow in the case of said partial return of air.

13. Method according to claim 4, characterized in that step j) consists, in all the preferred embodiments of variants or others, involving at least two filters, in establishing a permanent round-robin of part of filtered air, taken as close as possible to the discharge point of said respiratory assistance system, for example a ventilator, to return it equally distributed over the outlet of each filter, more precisely between the outlet of each filter and a selection means of each filter disposed on the air inlet common to all the filters on the suction of said respiratory assistance system; such a circle is used in said sequences safety controls for assisted replacement of filters or said seals; in the variant or other preferred embodiments comprising two filters, the selection means may advantageously be common to the two filters and be in the position normally open on both sides by default of current or of said controlled sequences.

14. Method according to claim 4, characterized in that step k) consists in interposing, between a filter and its clamping support, conforming or not conforming to standards EN 148-1 and DIN 3182, a seal system designed to produce at least the functions of sealing, limitation of compression, physical perception of the end of manual tightening, detection of the end of tightening and of. normal presence of a filter on its support, for example by an electrical contact established under a controlled atmosphere internally to such a seal.

15. Method according to claim 4 characterized in that step I) consists in using and analyzing all the measurements, calculated information, available states to identify from said measurements, information, states, the nature and location of a fault. , determine the immediate action that will be requested from a wearer to correct such a defect or, in the preferred and variant embodiments or other, involving at least two filters, to trigger said commanded safety sequences carrying out the selection and physical isolation, with confirmation of the isolated state, of the worn or most worn filter or of said defective seal, allowing a wearer to choose to leave a risk zone or to opt for the correction of such a default by being assisted for the actions that will be requested, while retaining the benefit of protection.

16. The method of claim 4, characterized in that step m) implements a communication of information and instructions using very low non-audible frequencies generated by a resonator or a vibrator, transmitted directly to the column d air of said air delivered communicating with the interior of said face piece, so that this vibration is directly perceptible on the face of a wearer, or transmitted directly by a vibrator placed as close as possible to the skin contact. a wearer, without requesting the sense of hearing.

17. Method according to claim 4, characterized in that step n) implements a method of modulating such vibrations giving at least the information and instructions useful for maintaining the protection of a wearer and for the simple actions which are requested for this purpose, in general such a method uses a very low fixed non-audible frequency appropriately modulated and necessarily comprising several levels of modulation as a function of the level of operating safety observed by such a process on such a system. respiratory assistance, for example extreme: - the absence of vibration would indicate normal operation and protection provided; - vibrations at a fixed frequency with more or less long and symmetrical, continuous or discontinuous modulations would indicate degraded operation remaining under control or the detection and location of faults that a wearer can immediately correct; - vibrations at a fixed, unmodulated and continuous frequency would indicate to the wearer that his protection under conditions of sufficient security is no longer ensured, that he must press said face piece on his face and imperatively leave the risk zone without haste or haste; such a method includes means of local display complementary to this information, or any other appropriate means, for any person carrying out surveillance or providing assistance and rescue to a carrier in difficulty or unconscious, for example presented in the form of a chronogram modulated in the same way as in the examples above, allowing this person to know exactly and in the same way the operating state and the level of protection provided to a wearer and to be able to act externally on this protection; such a method includes the additional recording in a memory area of this information and more generally of any useful and exploitable data in real time or deferred for the control and control of such a process and of such a respiratory assistance system. .

18. Method according to claims 4 and 15, characterized in that step o) consists, in the preferred embodiments and variants or others, involving at least two filters, to be triggered voluntarily by the maintained loosening of a filter, detected as a fault, said commanded safety sequences which physically isolate the filter, with confirmation of the isolated state, and initiates an assisted replacement sequence of the filter or of said filter seal as the case may be; such an emergency replacement sequence is carried out without losing the benefit of protection or contaminating the pipes concerned which remain pressurized, doubly blocked on either side of said circle of filtered air, with a leak rate voluntarily limited to a mechanical shutter valve directly in contact with the outside; such a replacement sequence includes a timed return to normal operating mode after replacement, purging of the circuits before final tightening of the filter and verification of the states; in such a method and on such a respiratory assistance system, such a replacement sequence never stops the assistance means, for example a ventilator, which remains controlled as a function of said measurements, information, states analyzed.

19. The method of claim 4, characterized in that step p) consists in adopting in said selection, coupled in normal operation, a control logic decoupled from the two shutters corresponding to a normally closed state by default of current or ordered. Such a closure carried out on a small section is deemed to be tight and thus prevents any significant return of said substances from the atmosphere through said selection. Such control logic supplemented by: the presence of said mechanical shutter valve on the outlet of each filter toward the aspiration of the respiratory assistance system, the default fixed tension exerted by a spring on said diaphragm / valve disposed between said total return of air and putting it entirely in the atmosphere, maintains the protection in an operating mode with free ventilation in the event of a power failure, without risk of carbon dioxide accumulation inside such an appliance or d 'such a face piece. The limited leakage on said mechanical shutter valves necessary for said controlled safety sequences occurs towards the outside on the filtered air side and poses no problem as soon as the flow rate of such leakage in expiratory phase is very low compared to expiratory flow. Sufficient respiratory protection is thus maintained and makes it possible to leave a risk zone without precipitation.

20. The method of claim 4, characterized in that step q) consists in using such a total air return completely put into the atmosphere in such an APRVA and in capturing it entirely at the outlet of a such a respiratory assistance system, for example for drinking, eating, providing care, etc., by occasionally and locally adapting said overhead protection to such an access or transfer airlock type, or more completely of a hood or a ventilated suit, to advantageously ventilate in a controlled manner such a tight, partial or total overprotection, of the transfer airlock type, hood or suit.

21. Method according to claims 2 and 4, characterized in that, according to an alternative implementation of step b), carried out in parallel with step a), said air is selected alternately, for this step, delivered as a bypass or all of said partial air return: • of said supplied air is selected at the same time as all of said partial air return is closed and its suction stopped, allowing a measurement of flow rate on the bypass of said supplied air and a measurement of the pressure on said partial return of air in pressure equilibrium with the interior of said face piece, in relative value with respect to atmospheric pressure, or in differential value with respect to pressure of said delivered air or, said partial air return is selected in full and its suction means activated at the same time as said supplied air is closed, allowing confirmation of flow rate of said return partial air on the means for measuring said substances and measuring the pressure on said air delivered in pressure equilibrium with the output of an assistance means, for example a fan, relative to atmospheric pressure.

22. Method according to claim 4, characterized in that step r) implements a complementary method of overlapping of step g), said method directly uses pure substances injected separately or in the form of mixtures, simulates at least the extreme and average phases of the real situations measured taking into account the effect of humidity; such a method, generalizable to all types of filter and to respiratory protection with free ventilation, comprises at least one or more of the following phases: 1) simulated maximum concentration: it is at least greater than a certain number of times, for example 10 times, the highest peak value recorded, generally for a short time, on a real work situation.

2) number of simulated maximum concentration phases: it is set according to the nature of the exposures observed in the field, for example five or six injection phases over a given period, for example one hour, makes it possible to cover the majority of situations encountered in Industrial Hygiene, the first when the test is started, followed for example by four or five others at more or less regular intervals,

3) simulated average concentration: the simulated maximum concentration phases are fixed, for example over said given period, so as to give an equivalent average concentration at least equal to a certain number of times, for example 20 times, the Value of the Actual average occupational exposure measured over the given period,

4) minimum average concentration to be simulated: if a measured actual Average Occupational Exposure Value is lower than a certain number of times, for example 20 times, a Limit Value of the substance tested for a given time, the phases of maximum concentrations will be fixed on said given period, according to such a Limit Value, so as to be at least equivalent on average to a certain number of times such a Limit Value, without ever exceeding the total theoretical capacity available of a filter ,

6) verification of the reversibility of the adsorption: steps 2), 3) or 4), as the case may be, are repeated on a new or regenerated filter, so as to simulate the progress of an operation over said given period. The air flow is maintained for some time, for example ten to fifteen minutes, after the last injection phase. The filter is then placed in the back-sweeping position on the bench and a flow of an appropriate gaseous fluid is maintained, until the total purging of the filter substance: the purge end time represents in these conditions the time during which an adsorption filter should be treated by back sweeping under the same conditions to be regenerated and that there are no more substances inside; to control such back-scanning, the quantity of said substances found must be comparable to the quantity of said substances introduced.

7) the maximum authorized continuous use duration: it is equal to said exit time from the substance noted in 5), apart from any other actual measurement provision of this duration,

8) the recommended cumulative duration of use: this is the time 7) divided by a safety factor which must take into account the maximum authorized availability period 9), apart from any other regeneration treatment provision or special such filters.

9) the maximum authorized availability period: period after which a filter must be replaced whether or not it has been used, whether in the case of an individual allocation or in the case of use collective, apart from any other regeneration or special treatment provision for such filters.

23. Respiratory protection device with assisted ventilation, characterized in that it comprises: a face piece (22) of which a rigid or semi-rigid part (22.0) hollow constitutes a device for internal lateral or peripheral collection of air (22.4 ) directed towards the outlet (9) and returned to the level of the respiratory assistance and filtration system (1) where it is entirely rejected into the atmosphere; said face piece receiving the air supplied to the inlet (8) (22.3) is connected by at least one pipe (7) to said respiratory assistance system (1); said internal collection device (22.4) of said returned air is connected to a return air pipe (9), preferably constituted by a concentric pipe internal (9) or (9.2) to the air delivery pipe, or by a separate pipe connecting said outlet (9) of said face piece (22) to said respiratory assistance system (1); said device respiratory protection is characterized in that it comprises means (19), for example constituted by a centralized computer system comprising a microprocessor and making it possible to analyze and / or measure one or more characteristics of said delivered air and said returned air before it total rejection to the atmosphere, in order to control the effectiveness and the actual duration of use of filters, the tightness of such a face piece and the safe operation of such a device.

24. Respiratory protection device with assisted ventilation, according to claim 23, characterized in that it comprises conduits (6) carrying out a continuous and constant rotation of part of the filtered air between the discharge of said system d respiratory assistance, for example a ventilator (5) and the aspiration of said ventilator, also distributed on particular points located on said aspiration between a selection means (4) and a shutter means (3) (3.10), allowing the control, via the centralized system (19), of safety functions and / or assisted replacement of filter or seal (3.1), without losing the benefit of protection.

25. Device according to one of claims 23 or 24, characterized in that it comprises means (13) allowing: a) in a controlled manner, via the centralized system (19), the selection of said air delivered at the outlet of filters (8), (8.1) towards said face piece (22), or from said total air return (9), (9.1) or partial (9.2), from said face piece, for measurement and / or control purposes different parameters, b) control or current default, to close the pipes (8.1) and (9.1) to the venting (17)

26. Device according to claim 25, characterized in that it comprises pressure measuring means (12) [(12a) (12c)] (12b) making it possible to measure, parallel or independently to said selection of air ( 13), the air pressure on said air return, total (9.1) (9) or partial (9.2), with respect to or independently of said delivered air (8.1) (8).

27. Device according to any one of claims 23 to 26, characterized in that it is provided with control and regulation means (10) making it possible to control and adjust the real positive pressure available in said face piece (22 ) in the case of said total return of air, by acting at the level of said respiratory protection device (1) on said total return of air through a device (10) comprising at least: a diaphragm valve (10.1) on which a spring (10.2) exerts a variable pressure adjusted by an adjustment means (0.3) controlled via the centralized system (19).

28. Device according to claim 25, characterized in that it comprises means for measuring flow (14) and centralized processing means (19) allowing: - to measure differentially or independently the air flows on the branches of said air supplied (8.1) and said total air return (9.1), respectively calculating the flow rates of said supplied air (8), and said total air return (9) from the memorized coefficients of ratio of flow rates [(8 ) / (8.1)] and [(9) / (9.1)], calibrated during construction on a fixed restriction (16), or line 17 or the measuring means (14) serving as a restriction, or, - d '' affirm the presence of a flow on said partial return of air (9.2) to the analysis means (15).

29. Device according to claim 28, characterized in that it comprises centralized processing means (19) making it possible to calculate differentially, in the case of said total air return (9.1) (9), the instantaneous air demand and / or average of a carrier.

30. Device according to claim 28, characterized in that it comprises centralized processing means (19) making it possible, in the case of said total return of air (9.1) (9), to calculate the average leak rate of air to the atmosphere of such a face piece (22) differentially between the average flow rates measured on said delivered air and said total return of air.

31. Device according to any one of claims 23 to 30, characterized in that said centralized processing means (19) making it possible to control and adjust the flow of said supplied air (5), so as to obtain a flow on said air delivered at least equal to the sum of the flows (a + b + c) below: a. said average air demand of the wearer, b. said average air leak to the outside, c. a fixed additional value or advantageously proportional to said average air demand of the wearer determined on said total air return.

32. Device according to any one of claims 23 to 31, characterized in that it comprises means for detecting said substances (15), making it possible to differentially measure the concentration of said substances on the air delivered, between an initial state recorded at the commissioning of filters and the evolution of these concentrations during actual use, in absolute value and / or in drift per unit of time, to determine their instantaneous efficiency and / or the limit of duration of use ; said substance detecting means comprising those allowing the measurement of the relative humidity, which means for measuring said relative humidity necessarily include the means for measuring the temperature.

33. Device according to any one of claims 23 to 32, characterized in that said means (15) make it possible to measure alternately, by means of said selection (13), the concentrations of said substances in said total or partial air return and said air delivered.

34. Device according to any one of claims 23 to 33, characterized in that it is provided with centralized processing means (19) making it possible to differentially calculate the leak in substance towards the inside of such a face piece and control it (5) (10), therefore to assess the actual exposure to substances with the wearing of a protection, independently and in addition to the breakdown concentration of substances measured on said air supplied at the outlet of the filters.

35. Device according to any one of claims 23 to 34, characterized in that it comprises means (3), for example integrated in a seal, making it possible to actively check or control: the tightness produced by such a seal between a filter and its support (3.1) (3.1a) (3.1b), the clamping pressure exerted on such a seal (3.3), the perception of the end of manual tightening of a filter on its support through such a seal by a stop (3.2) (3.4); detecting and confirming the normal presence of a filter on its support through such an electrically conductive seal and stopper by closing the electrical contacts established under a controlled atmosphere through the plugs (3.7a) and (3.7b ) and their bases (3.6a) and (3.6b); such a seal is held in position by an appropriate device, for example the plug (3.7a) allows such retention by being pressed on a base fixedly fixed in the pipe (3.6a), such a base is connected to an electrical circuit at through a watertight pass-through (3.8); in such an example, the plug (3.7b) is inserted in a floating manner on a connector (3.6b) connected to a flexible extensible wire itself connected to an electrical circuit through a sealed pass-through (3.8); the extraction of such a seal is carried out by a suitable device, for example an extraction ring (3.5) integrally fixed on a rigid part of such a seal (3.2).

36. Device according to any one of claims 23 to 35, characterized in that it comprises centralized processing means (19) making it possible to maintain the protection at a sufficient level in the event of degraded operation, on a single filter or on the remaining filters, after selection (13), detection (15) and isolation (4) of a worn and defective filter and / or seal (3.1).

37. Device according to any one of claims 23 to 36, characterized in that it comprises information and or alarm means (20), (20.2) making it possible to inform a wearer without being interfered with by his environment and without signaling it in its environment by using very low frequency vibrations that are not audible.

38. Device according to any one of claims 23 to 37, characterized in that it is provided with centralized processing means (19) generating such very low frequencies making it possible to inform a carrier (20) or (20.2) about the only specific faults in the maintenance of its protection with request for simple and assisted action to maintain or restore this protection, displaying (20.1) additionally, for example in the form of a chronogram modulated in the same way, the same information for all other person likely to assist a carrier, recording in real time in a memory area (21) any useful information or data that can be used in real time or in real time for the control and monitoring of such a process and such a respiratory protection device.

39. Device according to any one of claims 23 to 38, characterized in that it comprises means (4) [(3.) (3.1) (3.10)] (13) (15), controlled and / or ordered via the centralized system (19) allowing optional and assisted replacement of one (or more) filter (s) and / or one (or more) filter seal (s) in an emergency situation, without losing the benefit protection, or pollute the pipes which remain pressurized and doubly closed (3.10) (4) under air sweep through a deliberately limited leak on a shutter valve (3.10) brought into contact with the outside.

40. Device according to any one of claims 23 to 39, characterized in that it comprises means [(10) (10.1) (10.2)] (13) on such a total air return and (3.10) ( 13) on said supplied air making it possible to maintain sufficient protection in the case of said total return of air and in the event of total failure of the respiratory assistance means (5) (1) using such face pieces (22) devoid of valve , valve or any other device requiring air.

41. Device according to any one of claims 23 to 40, characterized in that it comprises connection means (11) making it possible to complete the respiratory protection by a skin overprotection using such a total return of air rejected entirely at the atmosphere collected on the outlet of such a device to advantageously ventilate in a controlled manner overprotection watertight, partial or total, of the transfer airlock type or hood or suit.

42. Device for implementing the method of the method according to claim 22, making it possible to cross-check the determination of the real effectiveness of the filters by a method of simulating situations of extreme exposures carried out on a bench (30), from injections of pure substances, generalizable to respiratory protection in free ventilation, characterized in that it comprises at least one or more of the following devices: - an air drying installation (not shown in fig. 13) - an air flow control assembly (31), adjusted as a function of the average flow conditions in actual use of the filters - an air humidification device (32) comprising in the example described at least: water capacity, stirred by an appropriate means (37) and heated by an appropriate means (38) to recreate by continuous vaporization, if necessary, humidity conditions comparable to those encountered in r situations they exhibit; this humidifier makes it possible to test by comparison and all other things being equal, the effect of this humidity on the efficiency of the filters used - a buffer capacity (34) of a known volume of gas stirred by an adequate means (37) , for example about 30 liters corresponding to the volume of air inhaled for about one minute by a person making a small effort; a recording detector being therein for example introduced or connected (36) for instantaneous concentration measurements at the input of the filter. - devices for introducing (33) known quantities of pure, gaseous or liquid substances, separately or in the form of mixtures, into such a capacity and a bypass system (33.1). - an airlock (35) allowing the filter to be tested to be connected to the capacity, in the direction of normal use (35.1) or in the direction of back-sweeping (35.2). - a device making it possible to connect a recording detector (36) after the filter.