FR2865654A1 - Respirator with blower protecting method, involves collecting air sent by protecting device, on exit of side part that does not have valve, and using air recycling operation in controlled sequences of filter replacement operation - Google Patents

Abstract

The method involves collecting total or partial air sent by a respirator with blower protecting device (1), on an exit of a side part (22) that does not have a valve, via an inner concentric duct (9). A centralized computer system (19) permits to analyze and measure characteristics of the air that is then recycled, where recycling operation is used in controlled sequences of filter replacement operation. The characteristics are measured to control the operation of the protecting device. An independent claim is also included for a respirator with blower protecting device.

Description

Method and devices for full control of protection

  assisted ventilation based on the use of filters

  The present invention relates to a method implemented on a respiratory protection device with assisted ventilation, allowing, in actual use, total control of the uses of adsorption filters, actual positive pressure and sealing in a facepiece; this method and its implementation on such an apparatus also allowed, in a complementary way, to cross-check and validate a method of testing the efficiency and the life of such filters in simulated exposure situations on a bench.

  Field of the Invention: The method and apparatus for ventilator-assisted respiratory protection (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, to preserve the health of people against any aggression of substances for which there is a filter and, preferably, a detector for the complementary measurement of such substances. These areas are all those where the ambient air carries molecules or dangerous particles such as: industries manufacturing or using or using such molecules or particles, whether these industries are in a normal or degraded mode of operation or in a situation crisis, the protection against harmful gases spread by a belligerent (acts of terrorism or state of war), the fight against unconfined fires, certain natural phenomena such as volcanic eruptions, etc. STATE OF THE ART Respiratory protection devices (APR) based on the use of adsorption filters are commonly used against the risks associated with the inhalation of 3o chemical substances.

  The effectiveness of the adsorption filters used varies according to many parameters, the main generally accepted are known to those skilled in the art: the nature of the substances encountered and their physicochemical properties, the nature of the adsorbent used: surface area or microporous volume, pore diameter, acidity or basicity, behavior with respect to water vapor, humidity and air temperature, the risk of interference between substances which may be the origin of selective adsorption and desorption phenomena, the case of water vapor is a particular example.

  This multiplicity of parameters, and the multiplicity of situations of possible applications in the field, make it difficult to use and control such adsorption filters in the respiratory protection.

  This difficulty is one of the main reasons why those responsible for prevention, based on a precautionary principle, hesitate to prescribe them for respiratory protection against the risks of exposure, especially for the repetitive situations usually encountered.

  The guarantees offered by such filters have however progressed through the implementation by manufacturers of standardized tests. These tests are used to indicate the general uses of these filters and their compliance with minimum performance and efficiency requirements.

  However, these tests are performed under special conditions (Figure 1), most often far removed from the reality of situations or operating conditions encountered in the field (Figure 2).

  This way of operating the adsorption filters has many disadvantages which all juxtapose.

  Standards, and, in an associated way, manufacturers because of the commitment of their responsibility, introduce important safety factors regarding the recommendations of uses. They refer, in many cases, the determination of the conditions of implementation of these filters to the personnel of the prevention and their responsibility.

  Prescribers, who are directly confronted with this employer's responsibility and with their regulatory obligations to provide resources, are increasingly adopting a "precautionary principle" prohibiting them from taking or managing any risk.

  Filter users do not have, in many cases, a procedure adapted to the actual conditions of use. They use it anyway and at best throw the filters after a single use, or, at worst, after a time of variable use but rarely controlled.

  The organizations or institutions referents in the field who, through the conclusions of numerous studies on the subject, pose the limits of the respiratory protection based on the use of the adsorption filters, at least with the free-breathing masks commonly used . For example the INRS in France in the ND 2123-178-00 - documentary note n 178, 18'trim. 2000), where the authors conclude: "the use of open-vent gas masks is not a fully satisfactory solution to a gaseous pollution problem in the industry and should not replace collective protection and should only be suitable for short periods of time and for low-toxicity vapors "Some reference bodies, with the aim of improving knowledge of the behavior and performance of filters, especially in real-life situations, are planning to carry out different studies. For example, the INRS in France reports on its website, on the one hand, a study project under the following title: "Development of a set of benches for testing compliance with CEN standards anti-gas and vapor breathing protection filters "; in this study, in addition to the necessary certification, the author announces that he plans to test the filters by reproducing real conditions of use, on more complex substances or mixtures of substances, with different flow rates, taking into account the effect of humidity; and on the other hand, a study project entitled "Determination of solvent exposure profiles and comparison with short-term limit values", certainly to better understand the reality of substance concentrations in real exposure situations, probably with methods comparable to those used in the tests shown in fig. 2 and 3 which are the basis of the process of the present invention.

  These study examples will better reflect the reality of the situations encountered. It is very common in industrial chemical processes to be exposed to a risk of exposure to mixtures of substances that are not taken into account in standardized tests. It is common to encounter large variations in the concentration of substance (or mixture of) during the same exposure situation. This is particularly the case for maintenance operations or with breach of containment. This type of study will certainly improve the practical knowledge on the behavior of adsorption filters employing an adsorbent, generally a variety of activated carbon, associated or not with other active supports, following physical adsorption processes I desorption yet known and commonly applied in areas such as industrial gas treatment and purification, gas sampling and pollutant analysis.

  Quite paradoxically, one may fear that improving the knowledge provided by this type of study on the behavior of filters will not necessarily simplify their implementation for a prescriber or a user, even if it will be made theoretically safer. There can be a reasonable expectation of an opposite effect, by increasing the complexity of the cases to be treated, associated with a precautionary principle that will be more and more asserted, thus moving away from facilitating the operational use of these protections. respiratory.

  In the current state of the art and current common 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 aforementioned fields to be able to fully utilize adsorption filters in respiratory protection, which are effective, particularly suitable for industrial hygiene and easier to use.

  It is also necessary for any manager, beyond his obligation of means, to show that the protections made available to his staff are effective, controlled and under control.

  In addition, for intervention personnel or military personnel, there is a need to ensure maximum protection of the technological possibilities available to guarantee their operational capacity, in the face of risks and threats of chemical or other attacks, and allow them to carry out their missions.

  The way in which the adsorption filters are to be carried out must be re-examined on the merits. This examination must take into account several aspects of different nature, sometimes contradictory, for the best possible result and a clear objective, to reduce the exposures: professional in the current state of the industrial processes, which does not forbid to continue to improve these last, 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, possible to control, economically bearable, accepted by the users, a discreet operation.

  A beginning of answer to this problem is brought by the majority of the manufacturers who propose Electrically Controlled Assisted Respiratory Protection Device (APRVA) or by microcontroller. These devices remain based on the use of adsorption filters. They may have, outside the filters, operating and protection characteristics comparable to those obtained with the Respiratory Insulating Devices (ARI), for a weight about 10 times lower and often a much better ergonomics and autonomy.

  These devices, such as the one used for the tests on which the method of the present invention is based, involve electronic controls with different operating alarms. These regulations, known to those skilled in the art, are based on the processing of information provided by bodies such as turbine rotational speed sensor, flow sensor, pressure sensor, etc., which interact either on the speed of rotation of the turbine is on the power delivered to the turbine by a modulation of the torque: current and voltage, to maintain the best conditions such as for example: positive pressure delivered to the facepiece used, minimum flow, adjusted to the construction or with respect to a set point, for example a minimum flow rate of 120 l / min with the apparatus used for the test examples underlying the present invention.

  The adsorption filters used in the test examples on which the process of the present invention is based are of the AXP3 type. They are normally reserved for substances with a boiling point <65 C and free ventilation. They are especially suitable for substances with a higher boiling point for which A2 filters are usually used. AXP3 filters offer greater efficiency and greater capacity. They contain a load of 335 cm3 of activated carbon with a specific surface area greater than that contained in the A2 filters, combined with a P3 filtration to block the dust and / or aerosols.

  The standardized tests carried out on the adsorption filters, according to standard NF EN 141 (replaced by PR NF 14387) in free ventilation, or NF EN 12941 and 12942-Al in assisted ventilation, are intended to guarantee users a minimum time of use under flow and concentration conditions laid down in the standards. These standards are based on the determination of a breakdown time, by progressive saturation of the adsorbent sites, after which time a small percentage of the test concentration indicated in the standards is reached. With an APRVA, the airflow on the adsorption filters can be much greater than in free ventilation, with repercussions on the duration and / or the maximum concentrations set in the standards. In addition, a time limit recommended by the supplier must be taken into account.

  An order of magnitude rule is applied to adapt this usage time according to a really measured average concentration. This rule is roughly established from the conditions of the standardized tests, that is to say for a constant substance concentration and on the assumption of conservation of the mass of this substance on the adsorbent tested, it only takes into account the parameter capacity of the filters. It does not always take into account the dynamic behavior of the substances on the filters, especially in real exposure situations where the concentrations are very variable, most often in a field advantageously far from these capacity limits.

  The set: device + filters + facepiece is normally subject to CE approval according to standards: EN 12941 or EN 12942 and a minimum performance rating that varies depending on the facepiece used. The performance of other APRVA components, such as different facial pieces, for example, are well evaluated in the standard Nominal Protection Factor determination tests. Although the performance of these facepieces is a different issue from that of filters, the overall effectiveness of respiratory protection and the Assigned Protection Factor provided in real life situation largely depend on the performance of these other components, even it is generally accepted that the use of assisted ventilation improves the performance of components such as different facial parts compared to a Free Ventilated Respiratory Protection Device (APRVL). This different issue must necessarily be taken into account in a substantive review.

  It is likely that standard tests of adsorption filters, in particular with APRVAs, based on the adsorption capacity alone and the hypothesis of the conservation of the mass of substances, are no longer suitable for Industrial Hygiene, or this capacity is rarely used to its limit, and the actual conditions of use in which the dynamic behavior of the substances on the filters becomes predominant. This is even more true for military purposes where the concentrations of aggressive substances or agents, which by their very nature are very toxic, are most often encountered at low or even very low and scattered concentrations, circumstances in which the only capacity can no longer indicate all of them. filter applications under guaranteed safety conditions.

  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 situation of exposure much higher operational performance than those indicated in the standards or notices.

  It is therefore primarily adsorption filters that control the implementation of these protections, and it is at this level that their uses must be validated in actual situations of exposure or, failing that, additionally, tested in simulated exposure situations on a bench.

  It is then by the total control of the conditions of application of such filters on devices that operational solutions can be proposed.

  Some inventors and / or manufacturers have proposed solutions in order to better control the performance of filters and / or APRs and inform users about their necessary replacement.

  In the document WO-01143827, the technique used is complex and uses a device consisting of several devices, relatively heavy and bulky to wear for a user. Its main purpose is to continuously determine the actual Assigned Protection Factor of a complete set of respiratory protection (mask + filter) carried by an operator and to associate, by video recording and teletransmission means, the situations encountered during the wearing of the described system. This invention is not primarily intended to determine the performance of the filters to deduce general characteristics on their actual useful life, extrapolated to other similar situations of exposure.

  In US-6040777, the technique used is complex and uses a system independent of an APR worn by a user. Its main purpose is to continuously evaluate the protection time or capacity remaining available on filters carried by an operator in order to inform him about the replacement of filters. This assessment is based on methods published by the AIHA (G.O. WOOD, January 1994, p 11-14). Such a system must be preconfigured before any use for the conditions that will be encountered on the exposure situation (s) to be protected. Such a system does not deal with the case of mixtures of substances, since it evaluates, a priori, an expected variable at the outlet of the filters from data relating to a single substance and ambient measurements practiced at best at the input of the filters. . Even assuming that these measurements could indicate a total concentration level of substances, using for example a non-specific global detector, this would not ensure a sufficiently safe operation of the proposed device, each substance having a particular behavior on filters . This device does not seem to be suitable for multiple uses of the same filters, either by the same operator or by several different operators.

  Document US-5671730 proposes a system of assisted ventilation apparatus comprising, in addition to the usual means, a method of regulating the effective voltage delivered to a motor driving a turbine, by an electronic control circuit delivering such a voltage to this motor through a first means for measuring the intensity consumed by said motor and a second means for measuring the speed of rotation of the turbine, both of these means providing a signal to said electronic circuit for regulating the power consumed by the turbine , therefore the mechanical work done by such a turbine, which is proportional to the air flow.

  In GB-2249963, a visor-type facepiece is described. This face piece has laterally, on a hollow rigid portion, organized openings for distributing the air inside of such a face piece.

  In document US-2002062830, is proposed a device with assisted ventilation comprising besides the usual means, another method of regulating the air flow directly based on the total measurement of the air flow, through a means of measuring the air flow. speed of rotation of a turbine freely driven by the flow of air passing through it and placed after the fan. The signal provided by this means directly controls the power delivered to the motor driving a fan.

  In US-5950621 is proposed a method of management of respirators with assisted ventilation. The description of this method to largely refers to known means of the state of the art to: identify all or part of the components of such devices, operate and control these devices. On the particular point of determining the lifetime of filters, the proposed method is comparable to that described in US-6040777, the main purpose of which is to continuously evaluate the protection time or the capacity remaining available on filters. The proposed method, however, has two notable differences with the previous one: the first is that this evaluation could, according to the inventor, be made directly on the respirator worn by an operator that contains essential information: the cumulative total volume of air passed on the filter; the second is that no measurement of the concentration of substances likely to be encountered in the ambient atmosphere is carried out during the use of the filters, these concentrations are assumed to be known and are calculation variables previously stored on such device through a communication interface with a computer accessible to an administrator. As in the previous document US-5950621, already commented, the proposed method takes into account only the capacity of the filters, and would be even more uncertain in the case of the proposed invention due to the absence of these concentration measures. of atmosphere in use. The other means described in this document, such as flow sensors, pressure sensors, fan rotation speed sensor, etc., associated with an implementation of the microprocessor-based (PIC) or electronic data processing means or states, including in particular an alarm interface of a user by conventional means: visual incorporated into a facial piece or audible, largely refer to the current state of the art.

  DE-19543056 and DE-100130266 describe test devices which mechanically reproduce different rhythms of a user's actual breathing. The filters are tested on this device under real-life conditions, directly on hazardous areas, or on samples of reconstituted or collected gas in these areas. The main objective is to determine under these conditions by measurements of substances performed at the outlet of the filter, the time during which such a filter will be effective to protect a user, in particular according to the respiratory rate.

  In US-6162281, the technique used is complex and ro requires a modification of the filters. Its main purpose is to determine the end of the efficiency of such a filter by making measurements on several areas of the adsorbent relative to a reference taken from the first input zone of the filter to compensate, according to the authors, the drifts of the detector. The main purpose of this invention is to anticipate the appearance of the substance at the filter outlet. Such a system using a non-specific global detector could handle the case of mixtures of substances and multiple uses, but it seems difficult to apply in an operational way and would require manufacturers, in addition to a necessary standardization of the construction, changes in their production lines. filters. In addition, such a device can only function properly if the concentration of substance is moderately stable at the inlet of the filter and if the principles of conservation and stability of the mass of substance absorbed on the support of such filters are verified.

  In another document, has been proposed a device comprising an optical fiber to be integrated in the construction of the filters and indicate the degree of saturation in substance of such filters. This device, according to its authors, is not very sensitive and has a relatively fast aging due to the humidity of the air. Such a device always requires manufacturers to modify their filter production lines.

  US-551288 discloses a device having a probe whose impedance changes upon exposure to vapors of organic substances, to determine the end of life of filters. This device, through the examples described, is insensitive. Such a measuring device is, according to its inventors, interfered with the humidity contained in the air.

  EP-0838243 relates to a method for fixing undesirable substances in the air on a support previously impregnated with a substance chosen for its odor and non-harmful properties. The odorant is displaced by undesirable substances to absorb above a certain saturation threshold of the absorbent. The smell perceived by a user allows according to the inventors to determine the end of life of such a support.

  Document US Pat. No. 5,559,296 describes a probe for measuring the concentration of substance in the air filtered by a cartridge. This probe is placed in a housing which can be inserted between a cartridge and a protective mask in free ventilation or on the pipe between a device with assisted ventilation and a mask. This probe, which must be sensitive to a large number of substances can not, in terms of technology and sensitivity characteristics, specificities, compete with mini measurement or detection devices that are now offered by specialized manufacturers.

  According to the document DE-19916476, tracking memories are incorporated into their manufacture in each component component respiratory protection, for the dual purpose of administrative or regulatory management of equipment and a control of the adequacy of these materials to their area of use, through an access portico comprising a reader of such memories. Such a device could be used to count the time of presence on a risk zone, assimilated to the time of use, and again refuse access to such a risk zone if a time limit of use is exceeded. Such a device has a triple disadvantage for this control function: it does not differentiate the time zone effective use time in the case of multiple uses, it does not take into account the variations in concentrations of substances encountered, it does not does not take into account the dynamic behavior of such substances on filters.

  US-5906203 discloses forced and / or positive pressure respirators. These devices utilize a valve system that includes a negative differential release air demand valve associated with a positive differential release air release valve (or flapper). Such a valve system is an integral part of the facepiece used, and guarantees according to the inventors, the permanence of a positive pressure in the facepiece. In fact, the operation of such a system necessarily involves short phases of "stop flow", moreover figured in this document, phases during which the risk of leakage towards the inside of a facepiece increases. . In addition, as in conventional systems, if a leak occurred on a facepiece, the air demand valve would remain permanently open necessarily requiring an increase in the airflow provided by the fan to hope to maintain a positive pressure to or in the facial piece. The proper functioning of such devices and such a valve system therefore remains conditioned to the perfect seal of a facepiece, sealing that is not verified or controlled in the invention proposed in this document. The other means described in said document, such as flow sensors, pressure sensors, fan rotation speed sensor, etc., associated with an implementation of the microprocessor-based (PIC) or electronic data processing or state processing means, including an alarm interface of a user by conventional means: visual or audible, largely refer to the current state of the art.

  In US-20031024529, describes a ventilation system of a protective suit in which is placed a respiratory assistance device and accessories, worn by a user. These assistance means distribute by a controlled means as a function of different measured parameters, the air flow delivered at the outlet of the filters between the inside of a facepiece, always comprising valves and / or demand control valves. of air, and the interior of such a combination. Such a system has several drawbacks, for example: It does not prioritize the entire flow of air available to the inside of the facepiece, ensuring first a maximum respiratory protection, then only reject it to the within such a combination, which method, if used, would ultimately produce at least the same effect on the protection provided within such a combination by allowing the use of a facepiece without a valve or valve; the placement of a respirator inside such a combination mortgages a large part of the possibilities of intervention or assistance by a third party in an emergency or makes them at least more difficult on such a device.

  In US-6575165, it essentially concerns a method and devices for quick connection of filters between a respirator and such filters comprising a physical locking of such a connection and its verification by various means, including one electrically resistant. This connection uses threads with large thread pitch on the filters and the housing of the filters on a device, allowing clamping of such filter in less than a turn on a conventional joint disposed at the bottom of the housing on the device. Locking is carried out at the end of clamping by engaging pins, males on the filters and females on the device. The inventors suggest that these lugs would be used to close a contact established through the probably metallic housing of a filter as soon as it is correctly locked, that failure to make such a contact could usefully condition the operation of the fan. and / or other additional functions such as for example the use of such a contact for hot filter replacement. The proposed method is completely captive of the proposed device in that it does not comply with DIN 3182, especially on the point of filter threads, which definitely prohibits the use of all the standard filters available at the moment on such devices. The method and the proposed device require the modification of the construction of the filters and the adoption of metal conductive housings, or non-metallic but with the addition of a conductive part between the male pins. The proposed device has resilient locking lugs and deformable on the device.

  The presence of a thread with a large pitch on such a connection has at least several disadvantages: the locking lugs support a strong loosening torque, which represents a risk of wear over time, at least for those made on the apparatus; the sealing on a conventional joint with such a thread is obtained on a very short tightening angle: about 10 against 30 with a thread according to DIN 3182; the alignment of the clamping planes: filter tip on seal at the bottom of the filter housing, directly influenced by the weakness of the clamping angle and locking with misalignment stress, is mechanically less good with less than one turn of tightening with the DIN thread that makes it over more than 2 turns, except to achieve a more precise adjustment of the threads, but certainly to the detriment of the ease and speed of implementation. Another point of the proposed method seems however prohibitive for uses in industrial environments where the need to resort to respiratory protection is often associated with the risk of presence of gas, sometimes flammable. The suggested solution of verifying the good locking of such filters through an electrically closed circuit and externally in the proposed solution, even under low current, prohibits the obtaining of the classification of conformity of such devices for such uses. the evocation of a method of hot replacement of such filters, a delicate operation certainly presenting great risks, can not be criticized on such a device for lack of device shown or proposed.

  In EP-0916369 another organization and another method are proposed for making a different connection of the components of a ventilator with assisted ventilation. The arrangement proposed uses essentially O-rings sealing on the opposite smooth parts of the various components that fit into each other. Regarding the particular point of the connection of the filters, the proposed invention differs from the previous one (US6575165) in two essential respects: the first is that the proposed arrangement retains in addition the threads of DIN 3182 on the opposite non-smooth parts such a connection thus allowing the standard default use of all standard filters, complying with DIN 3182, on such an arrangement, the second is that the physical verification of the good quality of such a connection is not realized in such an arrangement.

  In general, in all the solutions proposed in the aforementioned documents, for example the inventions described in EP-0916369 and US-6575165, the seal is always asserted, but never actively or directly verified.

  In US-6425393 are described a valve and its various arrangements. Such a valve regulates the positive pressure applied to the airways of a patient to transiently block the expiratory function in cardiovascular and respiratory resuscitation.

  In US-6575163 there is provided a method for calculating the instantaneous respiratory volume of a subject during respiratory assistance, comprising the steps of estimating the respiratory rate, the calculation of an indicator which remains constant as long as no leakage undesirable does not modify it, and the calculation of the volume of inspired air as a function related to the measured respiratory airflow and to such an indicator. the proposed method allows according to the inventors to maintain efficient respiratory assistance, even in the event of a major leak on the facial part of a patient. The proposed solution uses a pressure sensor directly placed in a facepiece as described in WO-0067286.

  In the document US Pat. No. 5,764,203, there is provided a mask comprising an electronic light modulation display unit for displaying measurement data, probably concerning the operation of a device coupled to such a mask, in the visual field of the wearer. of such a mask.

  Of the inventions set forth in the aforementioned documents, some, such as those described in US-5764203, US-6575163 and US5950621, characterize a present trend towards the complexification of facial pieces, thus making them more fragile, more difficult and more expensive. to maintain, often unfit for classification for uses in industrial environments where the risks of flammability or explosion can not be ruled out.

  The object of the present invention is to overcome the majority of the aforementioned drawbacks.

Presentation of the invention.

  The subject of the present invention is a method and a device for implementing this method, integrated in an APRVA, allowing a total control of the use of the adsorption filters, or filters in general, the total control of the protection offered. , total control of the operation of such APRVA.

  According to the method of the invention, all or some of the air which is sent to it by a respiratory assistance system filtering said air is collected on the outlet of a facial piece made for this purpose. said total or partial return of air, through a suitable air line up to said respiratory assistance system, and this air return is used for the measurement of one or more operating parameters of said method and said system of air assistance by the implementation of operations or means appropriate to the measures or controls operated.

  This device is also remarkable in that it preferably comprises a total return air duct to the APRVA, for example consisting of a concentric pipe internal to the air supply pipe or a separate pipe.

  This device is remarkable in that it comprises a continuous recycling and rotates in a circle of a part of the air between the delivery of the assistance means and a particular point on the suction of the assistance means allowing to perform controlled functions of safety and / or assisted replacement 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 output of the filters the said delivered air to such a face piece or the said return of air, in whole or in part, of such a facepiece, for the purpose of measuring or checking various parameters - measuring, parallel to said selection or independently of said selection, the air pressure on said return air, total or partial, with respect to said delivered air or relative to the atmospheric pressure, and the flow rate of air on said total air return with respect to the flow rate of said delivered air, to control and adjust the actual positive pressure available in such a room in the case of a total air return, by acting on the means of assistance on said total air return; - Differentially measure, in the case of a total air return, on said total air return the instantaneous and / or average air demand of a carrier; calculating differentially between said total air return and said delivered air, the total air leakage rate to the atmosphere of such a facepiece; - control and adjust the flow rate of said delivered air so as to maintain a flow rate at least equal to the sum of the flows: [a carrier's air demand + total air leakage to the atmosphere + an additional flow rate, fixed or advantageously proportional to said air demand]; - Differentially measure the concentration of substances on said delivered air, between an initial state measured at the start of filters and the evolution of this concentration during actual use, in absolute value and / or drift per unit of time , to determine the instantaneous efficiency and the limit of duration of use; measuring alternatively by means of said selection the concentrations of substances in said total or partial air return, and said delivered air; differentially calculating the substantially inward leakage of such a facepiece, thus the actual exposure to substances with protection, independently and in addition to the substance breakdown concentration measured on said delivered air; and control this leak; - Recycle continuously, rotates in the round on the assistance means, a portion of the filtered air for the purpose of performing controlled sequences of safety.

  - check or actively check: the tightness achieved by a seal between a filter and its support, the clamping pressure exerted on such a seal, the manual perception of the end of normal tightening of a filter on its support, the normal presence of a filter on its support, through such a seal; - maintain sufficient protection in case of degraded operation, on a single filter or on the remaining filters, after detection and isolation of a filter and / or worn or defective seal; - inform a carrier without being interfered with by his environment and without notifying him in his environment by the mere use of very low non-audible frequencies; - inform a carrier of the only defects relating to the maintenance of his protection with simple and assisted action request to maintain or restore this protection, - perform the optional and assisted replacement of one or more filters and / or filter seal (s) in an emergency situation, while retaining the benefit of the protection; to maintain a sufficient protection, in this case of a total return of air, in case of total failure of the respiratory assistance using such facial pieces; - Complete the respiratory protection with a skin protection using such a total air return, normally vented to the atmosphere at the outlet of such a device, to advantageously ventilate in a controlled manner a tight or partial over-protection, hood type or combination; - cross-checking the determination of the actual efficiency of the filters as shown by such a method on such a device, by a method of simulations of extreme and average exposure situations, performed on a bench and generalizable to the respiratory protection without respiratory support .

  The method and the device according to the invention provide numerous advantages.

  Used on such an APRVA, they allow to control the effectiveness and the real performances of the only filters, by the use of detectors of suitable interchangeable substances integrated in the operation of such APRVA and the measurement of the concentrations of substances on the air sent after the filters to a facepiece worn by a user, by a differential method between an initial state noted at the commissioning of an APRVA and any subsequent state occurring during actual use, measured in absolute value and / or derives from it per unit of time; they thus allow the determination of the end of life of the filters and eliminate the drift problems of the detector or the need to resort to a reference, reported in some documents of the state of the art.

  Used on an APRVA, they also make it possible to verify the tightness of a facepiece by using the same detector integrated in the operation of such an APRVA by practicing, by means of selection, differential measurements of concentrations. in substances between the air sent after the filters to such a face piece and the air returning, totally or partially, of such a face piece towards such an APRVA; it is no longer the Assigned Protection Factor that is thus determined, since it is no longer useful to measure the ambient air, but the actual individual exposure with protective port, without additional accessory or device to be worn by a user other than such an APRVA equipped with such a facepiece, with a better objectification of the reality of the results obtained.

  Used on such an APRVA, they allow not only the measurement, but also, according to the variants with full air return, the control and the maintenance of a real positive pressure in such a face piece by such an APRVA which comprises means for regulating the pressure measured on said total air return of such a facepiece, even in the case of large leaks on such a facepiece; such a facepiece having no mechanical member or valve or valve is robust construction and is not subject to inspection or regulatory visit. Such a facepiece eliminates the risk of inward leakage related valves or valves usually located on the majority of the facial parts, in the immediate vicinity of the inhaled air zone and directly in contact with the ambient atmosphere. According to the variants with a total return of air, these risks of leakage are displaced at a remote distance on the means of assistance and, if they intervened, could never be retro diffused in the inhaled air zone, taking into account the flow permanent air applied in such a facial piece.

  Used on such an APRVA comprising such a facepiece, they also allow, according to the variants with total air return, not only the measurement of the air flow delivered to such a facepiece but also the measurement of the flow rate of the air. air return of such a face piece, thus continuously monitoring and adapting the operation of such an APRVA to the user's instantaneous or average air demand, measured as being half the difference of the extreme flow rates or means between the inspiration and expiration phases, increased by a heel value which can be fixed or advantageously a function of such an air demand, making it possible to achieve maximum useful life for the filters, in particular in terms of standby position at rest or survival of a carrier; in the same way, the total leakage rate to the outside of such a facepiece is controlled by the difference between the average flow rate measured at the outlet of the filters and the average flow rate measured on the total air return of a such a facial piece.

  Used on such an APRVA, they allow, according to the variants with full air return, the maintenance of a sufficient protection to be able to leave without precipitation a risk zone in case of total breakdown of the ventilation system, even with the use of such facial parts, having neither valve nor valve.

  Used on such an APRVA, they also allow, according to the embodiments comprising at least two filters, with or without total or partial return of air, and comprising a continuous recycling of an air flow between the outlet of the fan and filter outputs, an automatic safety function and the 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 one filter and not another (s) or in higher concentration on one filter compared to another (s), a clamping or filter presence defect is detected by a gasket leak detector and clamping force limiter; said automatic safety function comprises a delayed controlled return to a normal operating mode after correction of the fault and verification of the states.

  Used on such an APRVA, they still allow, according to the embodiments comprising at least two filters, with or without total or partial return of air, and comprising a continuous recycling of an air flow between the outlet of the fan and the filter outputs, the use of said automatic safety function triggered by the voluntary manual release of a filter for a function of replacement assisted filters, or the replacement of such a filter seal which is possible on such an APRVA if, after the replacement of the filters, the substance continued to be specifically detected on the output of a filter, preventing the controlled return to a normal operating mode. As before, said assisted replacement function comprises a delayed controlled return to the normal operating mode after correction of the fault and verification of the states. All filters can be successively replaced in any emergency situation, without losing the benefit of the protection or risking to contaminate the pipes which remain pressurized and doubly closed under an air sweep through a voluntarily limited leakage. on a mechanical shutter valve in contact with the outside.

  Contrary to the method mentioned in document US-6575165, in such an automatic safety function and / or in the assisted filter replacement function, the fan is never controlled or stopped by the contact established through such a device. gasket leak detector and clamping force limiter, attesting to the presence of the filter on its support. The fan airflow remains controlled and adapted to the air demand of a carrier and can be decreased or increased depending on other programmed or measured parameters.

  This method and such APRVA use a user information method based on the use of a non-audible very low frequency resonator, transmitting such vibrations directly to the air column sent to the face of the user. user in such a facepiece, or transmitting such vibrations directly to a vibrator connected to such an APRVA and placed closer to the contact of the skin a carrier. This method, which does not solicit eyes or eyes, solves the problem of users who are visually impaired, hard of hearing or having reading difficulties, it solves the problem of use in noisy areas or the wearing of hearing protection is necessary, it also decreases strongly functional signature, especially visual and auditory for military purposes.

  Such a facepiece has no connection or electrical or electronic accessory, which allows easy classification for use in areas with risk of flammability.

  Implemented on such an APRVA, they do not require any modification or transformation of the filter production lines as has been proposed in some documents cited. The devices and the means used are integrated in such an APRVA, and are thus effectively protected.

  Used on such an APRVA, they allow, according to the variants with full air return, to supplement the respiratory protection of a wearer with a partial or total cutaneous protection against the attacks or absorption of harmful molecules or particles, by the over-protection hood type or ventilated combination from such a total return air collected at the output of such an APRVA and connected to such overprotection, before being discharged to the outside atmosphere, establishing advantageously controlled ventilation of such overprotection by such an APRVA advantageously placed outside such overprotection.

  The results obtained with such a method applied and tested on actual exposure situations are exactly cross-checked by a method of simulating comparable situations on a test bench, according to one claim, from direct injection of quantities of pure substances. separately or in the form of mixtures, without the need to produce expensive and long-time standard mixtures. Such a method and such a bench make it possible to generalize the tests on bench in all the cases of use of the filters, with or without assisted ventilation, on any type of support and for any substance. Such a test bench allows the examination and taking into account of the potential consequences of extreme operations, such as the effect of high concentration peaks or the exceeding of the recommended durations of use.

  The invention will be better understood with the aid of the following description relating to a presently preferred embodiment of the method and its variants, as well as with the aid of the appended figures for understanding the principles of operation. through some examples of realization. Throughout the description and in all the figures or drawings, the functionally or physically identical parts have the same root and / or the same registration 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 that would be used with a comparable method implemented on a similar device.

  Figure 1 shows an example of drilling curve recording in the case of a test performed according to CE standards.

  Figure 2 shows an example of a substance concentration record measured on actual exposure situations.

  FIG. 3 is a schematic view illustrating an example of state-of-the-art APRVA modified by adding two recording detectors to test the efficiency and actual behavior of the filters.

  Figures 4a and 4b illustrate exemplary facial parts of the state of the art visor-type and full face mask.

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

  FIG. 6 is a diagrammatic view of a preferred embodiment of an APRVA with a total air return by an internal concentric pipe, for use with a facepiece, made as shown in FIG. 7 shows an example of a preferred embodiment of a face piece with total air return by an internal concentric pipe, for use with an APRVA made as shown in FIG. FIG. 8 shows an exemplary preferred embodiment of a face piece with total air return by a separate pipe, for use with an APRVA made according to a variant of FIG. 6, wherein the total air return is directly connected to the pressure regulating means, as shown in FIG. 5.

  FIG. 9a is a detailed diagrammatic view of the leaktight seal and the clamping force limiter of the filter on the air inlet in all the preferred embodiments of the method and its variants. Figure 9b is a schematic detail view of the mechanical shutter valve on the air inlet in all the preferred embodiments of the method and its variants.

  Figure 10 shows examples of output time curves measured in actual exposure conditions.

  Fig. 11 shows an example of an overlap of output time curve and resolution of a substance, obtained by a real-life simulation method.

  FIG. 12 shows an example of a backscatter curve of a filter after a simulated or normal use. FIG. 13 is a schematic view illustrating a preferred embodiment of a bench for tests in simulated exposure situations carried out at from pure substances, and its main parts, Figure 14 shows an example of resolution curves of a substance on such a test bench in simulated situations, for average concentrations between 2 and 20 times the mean value of exposure (VME) regulated or recommended not to exceed average envalereur.

  Reference is made to the drawings to describe interesting but not limiting examples of implementation of the method and embodiment of the device according to the invention.

  In these drawings: the arrows represented by a simple solid line represent, in FIG. 5 the circulation of the air, the thickness of the line is approximately in proportion to the airflows conveyed; the arrows represented by a single dashed line & heavy dashed dashes designate the APRVA service orders; the arrows represented by a single dashed line represent the data and information processed by a processor which is useful to APRVA service commands; the arrows represented by a single line of strong discontinuous dashes represent the alarm and information commands to the user and / or delayed supervision; the arrows represented by a double continuous fine and dotted fine line designate the commands and data specific to the means of measurement of substances.

  The following abbreviations are used in the remainder of the 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.

  TLV: Exposure Limit Value, regulated or recommended not to exceed in 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 parts by volume, generally corresponds to cm3 of gaseous substance per m3 of air.

  CMR: Carcinogenic, Mutagenic, Reproductive Toxic Substances APR: Respiratory Protection Device in general except ARI APRVL: Respiratory Protection Device with Free Ventilation APRVA: Respiratory Protection Device with Assisted Ventilation ARI: Respiratory Insulating Device Adsorption: specifically concerns the reversible physical equilibrium phenomena (adsorptions * desorption) related to the trapping of substances on a porous support. By extension and trivialization of the use of this term in the respiratory protection, it can also include the cases where a substance, after being adsorbed (generally fast step), is complementarily fixed by an appropriate chemical reaction (generally slower step) . In the latter case, there is no reversible equilibrium. The adsorption capacity determined in the standardized tests correctly defines all the uses of such filters usually referred to as "chemical". In this case, and in this case only, the rule of proportionality between the time of use and the concentration, from the data indicated in the standards and the actual conditions of use can be applied relatively satisfactorily.

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

  Fig. 2 shows an example of recording the concentrations actually measured on exposure situations typically encountered during packaging or loading of substances with rupture of confinement, or during maintenance operations on industrial chemical processes, generally known as the most exponent. 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 many recordings in real exposure situations made during these tests and affirms the need to be able to have a protection adapted to this type of situation.

  Fig. 3 gives an example of implementation of the method on which the present invention is based, realized with a state-of-the-art APRVA (1) used in a first test phase: an APRVA (1) equipped with a facepiece (22) having a direct air outlet to the atmosphere (9) has been transformed to receive two separate onboard detectors, one on the intake air (15b) at the inlet of the filter, the other (15a), disposed in a shunt immediately at the outlet (7) of the APRVA (1) on the air at the outlet of the filters (8), feeding, via a pipe (8.1), a circulation cell of the sample (17) allowing the analysis of the air at the immediate exit of the filters. This modified APRVA (1) has been worn indifferently by different users on several operations deemed to be exponents under control, without ever changing the filters (2). The examination of the recordings (Fig. 10) on the sucked air (15b) and the repressed air (15a) showed that no trace of substance emerged from the filters (fig.10), even during very short and very strong concentration peaks at the inlet of the filters (several thousand ppm), which validated the efficiency of the filters used on these strong tips and allowed to go to a next step. Two separate detectors were used to suppress the common mode common 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 various documents, for example in WO-01/43827.

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

  In Figures 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 other elements or means or functions necessary for the operation of APRVAs of the state of the art 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 a separate pipe, or, alternatively, a partial return of air through a concentric pipe, for measuring different parameters; continuous air recirculation for the purpose of performing automatic or assisted safety functions; and using facial pieces as shown in FIGS. 7 and 8 1. an APRVA (1) equipped with filters (2) adapted on their bases with a suitable seal (3.1), an assistance means (5) controlled by a means (19), delivers a flow rate of air on the output of an APRVA (7) to a face piece (22) through an external concentric pipe (8); 2. such a face piece (22) receives said air delivered at the outlet of the filters (8), distributes it inside said room and returns it to such an APRVA in its entirety (9) by an internal concentric pipe or external, or partially (9.2) separated by an internal concentric pipe connected to a suction means (18). Such a facepiece does not include a valve, a valve, a so-called "air demand" or "positive pressure" device 3. the external concentric pipe (8) of said delivered air derives part of its flow in the pipe ( 8.1) to a restriction (16) and the output (17), for measuring various parameters such as: pressures (12), flow rates (14), substance concentrations (15), 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) serves to connect an external standard gas for a calibration or a rapid verification of said detector (15); 4. in a variant with full air return, the inner concentric pipe or the external separate pipe (9) of said total air return opens on the main pipe (9.3) which derives a part its flow in the pipe (9.1) and a r squeezing (16) to the outlet (17) for the purpose of measuring various parameters such as: pressure, flow rates, concentration of substances via pressure measuring means (12), flow measurement means (14) and substance detecting means (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) respectively allow the flow rates of the delivered air (8) and the total air return (9) to be calculated by the centralized system (19) from ratio coefficients of flows [(8) / (8.1)] and [(9) 1 (9.1)], calibrated at construction on the restriction (16) in the outlet pipe (17) or on such pipe acting as a restriction or on the restriction measuring means (14), coefficients stored on the centralized system (19); 6. in a variant with partial air return, the inner concentric pipe (9.2) of said partial air return is connected to a ventilation means (18) to a restriction (16), for measuring various parameters such as that: pressures (12), substance concentrations (15), flow measurement (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 exploit 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 the ventilation (18), in this position the flow measurement (14) only serves to verify the presence of a flow rate during the measurement of the concentration of substances; in such a variant certain functions or determinations are not possible: the regulation of the positive pressure (10) in such a facepiece, the determination of the air demand of a wearer, the total leak towards the outside of such a facial piece.

  7. said main line (9.3) of said total air return (9) is connected to a means for controlling and regulating (10) the positive pressure in said facepiece, controlled by the centralized system (19) from the actual pressure measurement available in said face piece (12a) (12b) and / or the differential pressure between the pressure at the exit of the assisting means (5) and that available inside such a piece facial (12b); such return of air rejected externally by a connecting means (11), can be captured for controlled ventilation hood overprotection or combination equipping a carrier.

  8. the assistance means (5) for said delivered air recirculates in a circle through the pipe (6) a small air flow equally distributed on both sides of the means for selecting and isolating the filters ( 4), used in controlled sequences of automatic security by the centralized system (19) to which they are integrated. Such a low air flow allows, 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 valve shutter (3.10 ) arranged on the same filter. This arrangement is reinforced by a small leakage flow voluntarily created through said shutter mechanical valve, ensuring the non-return of substance on said selection and isolation means (4) whose sealing can never be 100% guaranteed; 9. A non-audible low-frequency resonator / vibrator-type information and alarm means (20) having a sufficient autonomy is controlled by the centralized system (19) and vibrates the air column (8). ) in communication with the interior of said facepiece (22), such that these vibrations are directly perceptible on the face of a user; such means may be constituted by an external vibrator (20.2) placed closer to the contact of the skin of a wearer and receiving such vibrations. Both variants do not solicit the senses of sight and fouie. the information is formatted and limited to be useful in maintaining a holder's protection and the simple actions that are required for that purpose. The modulation of the delivered vibrations is complementarily and locally displayed (20.1) in the same format in the form of a timing chart 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 zone (21) in which the centralized system (19) records directly, in real operating time, any information or useful data which can be exploited later for the control and the control of such a process. or device.

  Such means comprising a memory zone is known in the art and can be read manually or automatically by means of a RF-ID type contactless reading method, for example to transfer such information or data to a computer program. for the purposes of exploitation.

  FIGS. 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 variant of such a face piece realizing such a return air, total or partial in such a concentric pipe, and their operating principle. More specifically, these figures show: a) an APRVA (1) equipped with filters (2) adapted to their bases with a suitable seal (3.1), and a fan (5) whose operation is regulated and controlled by a system centralized system known in the art (19), delivers a flow of air on the output of the filters (7) to a facepiece (22) by an external concentric pipe (8).

  b) a face piece (22) detailed in FIG. 7, provided with a very flexible face seal (22.1) and with a sealed sealing screen (22.2), is made to receive said air delivered at the outlet of the filters (8) and to distribute it inside the said face piece by orifices arranged for this purpose (22.3). The rigid portion of said shell-shaped face piece (22.0) has internal lateral outlets (22.4) which direct all of the air to an inner concentric outlet (9) constituting said total air return. Such a facepiece has no valve, no valves, or device called "air demand" or "positive pressure".

  c) the outer concentric pipe (8) of said delivered air has 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 sent back to said APRVA on a main pipe (9.3) having a connection with the pipe (9. 1) towards the pipe ( 17) and the detector (15).

  e) means for selecting (13) said total air return (9.1) or said delivered air (8.1) towards the pipe (17) and the detector (15) is controlled by the centralized system (19) to which said selection is incorporated.

  f) the lines (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 delivered air differentially established with respect to the atmospheric pressure advantageously transmitted through a sealed and deformable buffer capacity (12c).

  fi). the means (12b) measures the pressure of said total air return with respect to the pressure of said delivered air, allowing evaluation of the actual pressure available in said facepiece, when the pipe (8.1) is selected (13) to the pipe (17). The introduction of a restriction (16) into the outlet duct (17), or such restricting duct, or the restricting flow measuring means (14), permits maintenance in such a duct ( 8.1) the actual pressure available in such a facepiece regardless of the selection (13), therefore the continuous measurement of the differential pressure between said delivered air (8), (8.1) and said total air return (9), (9.1), without having to use a third measurement referring to the atmospheric pressure (12a) (12c).

  g) said substance detector (15) is disposed in an externally accessible compartment (15.2) allowing, without disassembly of said APRVA, the easy replacement of the type of measurement cell used (15.1) on said detector, which is managed by centralized system (19) to the operation of which it is completely incorporated. The addition of a restriction (16) in the outlet duct (17), or the use of such a restrictor duct or the restriction metering means (14), 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 facepiece (22), means comprising at least: a diaphragm / shutter valve (10.1 ), a spring (10.2) exerting a slight 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 facepiece (12a) (12b) and / or the differential pressure between the pressure at the outlet of the filters and that available within such a facepiece (12b).

  I) the pipe (17) has 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 rate values thus measured in the ducts (8.1) and (9.1) respectively allow the flow rates of the delivered air (8) and the said air return (9) to be calculated by the centralized system (19) from the ratio coefficients of flows [(8)! (8.1)] and [(9) 1 (9.1)], calibrated to the construction on the restriction (16) in the outlet pipe (17) or on such restricting pipe or on o the measuring means ( 14) acting as a restriction, coefficients stored on the centralized system (19).

  j) the pipe (17) also serves to connect an external calibration gas for rapid calibration or verification of said detector (15), without any disassembly and in any position of said selection means (13), provided that such an APRVA is in normal operation.

  k) the external part (8) of said delivered air comprises a connection with the duct (6) recycling in round a low air flow evenly distributed on both sides of the filter selection means (4) controlled in automatic security sequences by the centralized system (19) to which they are integrated. Such a low air flow allows after: selection of a filter by the means (4), closure of the corresponding shutter shutter on the other filter and confirmation of this closure by an established contact in the closed position between said shutter and a point contact located in the pipe, maintain a slight overpressure between a shutter said shutter and the shutter mechanical valve (3) (3.10) disposed on the same filter. Such a safety is reinforced by a small leakage rate voluntarily created through said shutter mechanical valve, ensuring the non-return of substance on said shutter shutter whose sealing can never be 100% guaranteed, especially in operations involving removal of a filter or replacement of such a seal (3.1) in operation.

  I) the part (3) detailed in FIG. 9a, comprises a sealing seal and clamping force limiter (3.1), performing the following functions: first, sealing performed on both sides on the parts (3.1a) and (3.1b); secondly, limitation of the clamping compression of the seal (3.1) by deformation of the resilient inner part (3.3), with perception of the end of manual clamping by mechanical stop between the two discs (3.2) through the internal contact points (3.4); in third and simultaneously, detection of the end of clamping and the normal presence of the filter on its base by closing under 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 joint; an appropriate device makes it possible to maintain such a seal in position: for example the plug (3.7a) allows the maintenance in place of such a seal, being pressed on its base fixedly secured in the pipe (3.6a), connected in addition an electrical circuit through a sealed wall pass (3.8); in this example, the plug (3.7b) is depressed floating on a connector (3.6b) connected to a flexible extensible wire itself connected to an electrical circuit through a sealed wall pass (3.8). Such a seal is easily removed and replaced by the outside using, for example an extractor (3.5) attached to one of the disks (3.2).

  m) the part (3) also comprises, on the output of the filters, a conventional mechanical shutter valve (3.10) consisting of two flaps (3.11), free of rotation on an axis (3.12), under tension of closure by a spring ( 3.13). Such a valve is fixed inside the pipe on clips (3.14) and closes such a pipe on the inner ring (3.15). such a valve is necessary in the automatic safety control sequences and contributes to the maintenance of the protection in case of failure of the respiratory assistance means (5) (1). Such a valve is easily replaceable by an access means (3.9) without disassembly of such an APRVA.

  Such examples of embodiment of APRVA and of facial parts, allow in all cases variants, with total or partial return of air: E to measure alternately the quality of the air at the outlet of a filter (8) and the quality of the air at the exit of a facepiece (9), at a programmed frequency adapted to the service of such an APRVA and at 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), thereby continuously determining the actual protection offered to a user, É a use made more secure of this type of protection by a dual differential analysis method on the centralized system (19) to which these methods are incorporated: - the first analysis is carried out between a zero measurement made on the air at the output of the filters, recorded at the commissioning of such APRVAs, and the evolution of this measurement, in absolute value and / or in drift per unit of t In the course of using such APRVAs, the second analysis is carried out between the air on the outlet of the filters and the air returning from such facepieces on such APRVAs.

  É a safety control controlled on a single filter, or the remaining filters, with maintenance of the protection, in the event of a fault specifically found on a filter and / or such a filter seal.

  The use of a non-audible very low frequency resonator / vibrator-type vibrating instruction / instruction passing means (20) powered by a stand-alone buffer battery controlled by the centralized system (19) and vibrating the air column in communication with the interior of said facepiece, so that this vibration is directly perceptible on the face of a user or directly transmitting these vibrations to a vibrator closer to the skin contact of a porter (20.2), without solicitation of the senses of sight or rouie. This means advantageously solves the problems of a hearing or visual impairment, or related to sound environments. Said facepiece does not include any mechanical or electromechanical or electronic member. The information method is voluntarily limited for the wearer to content useful for maintaining its protection and simple actions that are requested 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 fixed low frequency modulated appropriately necessarily including several levels of modulations, for example: absence of vibration => normal operation protection provided. fixed-frequency vibrations with continuous or discontinuous symmetric modulations: for example, positive pressure defect and / or leakage rate at the detected atmosphere greater than a threshold, or presence of substances detected differentially on the single air return, total or partial, in the absence of a positive pressure defect or a leakage rate to the atmosphere.

  fixed-frequency vibrations with intermittent long modulations, repeated at regular intervals, indicate for example to the wearer a partially degraded operation but remaining under vibration control at a fixed frequency, with a first series of rapid and symmetrical modulations requesting the stop of any activity, followed by a second series of asymmetrical modulations indicating the nature of the fault and the action required: for example detection of a poor clamping on a filter, or detection of presence of substance on the filter outlet in the absence of poor tightening on a filter.

  continuous fixed frequency vibrations for at least 1 minute => the APRVA service is no longer properly insured => flatten the facepiece on the face and leave the risk zone without precipitation, or change device.

  This information specific to a protection fault is additionally displayed on a general display means (20.1), incorporated in the centralized system (19), for any other person performing close surveillance or providing assistance and assistance to a wearer in difficulty. Such a display is advantageously made in the form of a chronogram modulated in the same way as on the resonator or the vibrator. This information may also be recorded in a form synthesized in the memory area (21) of an information storage means, for any subsequent use or deferred useful after reading such a memory by an appropriate means.

  However, as described above, any variant with air return does not allow the determination of the air demand of a carrier, the determination of the outward leakage of such a facepiece, the regulation of the positive pressure in such a facial 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 maintain at best a pressure setpoint within such a room i, in combination with the flow information calculated on said air delivered to the output of the filters (8). The combination of these various factors, combined with a substance detection, still allows a relatively safe operation of such an APRVA, but with the conventional disadvantage of a decrease in the duration of use of the filters necessarily related to the increased airflow. On the other hand, the flow of air returning from such a facepiece to such an APRVA for the measurement or control of various parameters, including the concentration of substance, can be guaranteed only by the addition of a fan Annex (18) creating a risk of depression in the pipe (9.2) supplying the detector (15), thus a risk of pollution by the external environment.

  Such embodiments of APRVA and facial parts, in any case allow variants with total return concentric air or separate: E to determine differentially on said return air, instantaneous air demand and / or average of a carrier, measured as being half of the difference between the extreme and average flow rates recorded between the inspiration and the expiration phases, E to determine differentially between the mean flow rates of said total air return and of said delivered air , the total air leak to the outside of such a facial piece.

  É to solve the classical difficulty encountered in case of power failure with such APRVA using such facial parts by the adoption of a control logic: default position: Normally closed two shutters shutters 5 to the output (17), on the selection means (13) thus preventing any return of substance by this output; default position: Normally Open the shutter at the output of the filters, common to both filters in a preferred embodiment described, on the selection means (4), thus allowing normal use of filters without ventilation; These provisions are supplemented by the presence of mechanical shutters with limited leakage (3.10.) On the inlet of the air assistance. Such a limited leak, necessary for the automatic safety functions, occurs outwardly on the filtered air side and poses no problem in this case since the flow rate of such an exhalation phase leak represents only a few% of the flow rate. expiratory, thus avoiding an accumulation of carbon dioxide within the assembly composed by such an APRVA plus such a facial part. Sufficient respiratory protection is thus maintained and allows to leave a risk area 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 method on which the present invention is based: an APRVA [FIG. 3 (1)] of the 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 that expose to the substance tested. Measurements were regularly made on the air leaving the filters. The filters remained voluntarily on the APRVA and out of any pollution, without clogging or treatment, to take into account the phenomena of internal migration of the substance in the filter. Several sets of filters were thus tested. They gave under comparable conditions of use the same cumulative use time, before appearance of the substance at the outlet. These recordings show that the growth of this output concentration is slow enough to allow its detection under good security conditions with APRVAs and facial pieces as shown in the present invention through the exemplary embodiments and variant, privileged or not ..

  Fig. 11 shows an example of overlapping of the results obtained in real conditions shown in FIG. 10, by a simulation method of exposure situations comparable to the same substance, carried out on a test bench (30) by injection of pure substance, on an identical filter to verify the behavior of the substance on such a filter and the potential consequences of strong peaks in concentration or exceeding the duration of use determined previously.

  The results of the bench tests (Fig. 14) confirmed several points concerning the adsorption equilibrium, very interesting points when applied to the control of these filters under real conditions of use and to the analysis of their operation: the substance was completely removed from the filters if the sweep was continued with air, wet or dry, co-current of normal use the substance emerged even more quickly if this sweep was done after each use and to counter to the normal direction of use.

  the filters after total desorption of the substance, regardless of the direction of desorption, recover their characteristics and could be reused a large number of times with the same performance.

  the cumulated usage time previously determined (Fig. 10) should be interpreted as being related to the output or resolution time 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, etc.).

  we will distinguish the exit time (start of appearance of the substance) of the resolution time (peak resolution maximum). The exit time, to a large extent, varies little with the amount of substance absorbed on the filter as shown in FIG. 14.

  The rate of increase of the concentration of substance at the outlet of the filter is generally slow enough to allow a direct and reliable measurement of a concentration threshold not to be exceeded, with APRVAs and facial pieces as shown. in the present invention through the embodiments and variants, preferred or not.

  the maximum concentration measured at the output of the filters is much lower than the maximum peak values measured at the inlet. The ratio of concentrations: output / input decreases rapidly in relation to the increase in the time of release or resolution of the substances. This phenomenon is due to the equilibrium and the fact that the adsorption filters also behave like true attenuators and capacitive integrators. This behavior will be even more verified if it will be high boilers and / or the filters will be used 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 (a situation which must certainly be encountered in the state of the art), the concentration The average output of the filters will tend towards the average of the concentrations integrated on the filters and usually met or measured on the corresponding exposure situations.

  the exposure peaks encountered in such exposure situations will never be inhaled by a protected user, even in the absence of rigorous filter management; at most, during the wearing period of the protection, it would inhale the average of the concentrations of substances incorporated in the filters and usually encountered in the exposure situations concerned.

  however, the important point to remember is that this will always result in a significant reduction in the value of the 8-hour average occupational exposure (see VME) and especially in 15 minutes (see VLE). This lowering will be all the more important as the duration of the port will be short and the exit time of the substance on the larger filters.

  This interpretation of the real behavior of the filters corresponds on average to the way in which they are used in the majority of the cases of the state of the art, this in the absence of a strict control or of a single use, although the single use does not guarantee that the previously determined output time will not be exceeded, depending on the duration of the single use and the exit time of the substance encountered.

  It is thus easier to understand the margins of safety adopted by suppliers on the use of adsorption filters, particularly in the case of substances with a low boiling point, which are precisely those where the exit times will be the lowest, and the current trend not to recommend the use of such filters on substances called CMR, for example carcinogens.

  In conclusion, knowledge of the exit time of a substance on an adsorption filter, operating in a domain far from its saturation and / or its capacity limit, used continuously under realistic exposure conditions, makes it possible to control the time during which such a filter will be effective for all its comparable applications in respiratory protection.

  Examination of an example of substances tested by the method on which this invention is based (FIG 3) on AX type filters illustrates these points. The substance is classified in group 18, with a VME of less than or equal to 10 ppm, for a free-running time of 50 minutes as specified in EN 371. The time given in the AX sheet insert provided by the manufacturer is 20 to 40 minutes, also for use in free ventilation.

  The effective use time actually measured for assisted ventilation at a constant flow rate of 60 Il minute, for a mean concentration measured over the duration of the situations actually tested (Figure 2) comparable to the 10 ppm VME given in the standard, is approximately 250 to 300 minutes before the appearance of the substance at the outlet of the filters (Figure 10). This time is 5 to 10 times higher than indicated in the standards or the manufacturer's manual. A priori evaluation of the duration of use, as recommended in various guides or instructions for use, from the standardized test data and interpolation of the two variables: concentration and breakdown time, interpolation based solely on the concept of capacity, taken as reference, would have indicated for the conditions actually tested (Figure 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 sole use of the supplier, which would make a maximum of 480 minutes which is the usual duration of a day working. This is not certain, however, because the same user, more or less specialist, could consider logically enough 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 (economic aspect and ease). In any case, 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 about 250 to 300 minutes of continuous use the user inhaled the substance; from about 400 to 600 minutes of continuous use it would inhale the average concentration of the substance encountered in the 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 concentration peaks encountered on these same exposure situations. On this single example, the difference between the extrapolated times from the standards test conditions, the indications of the suppliers in their instructions and the actual data recorded by a prescriber, (see: Fig. 10 & 14) anxious to make operational protection available to its staff effective, controlled and effectively used.

  It is certain that all the filters using only active carbons as adsorbent (A2, Al, etc.) function, and work poorly, in the same mode, including on substances with higher boiling point, but in this case at a less noticeable level.

  - 42 - This analysis of the operation 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 periods of storage between each use , phenomena that further deteriorate the conditions for 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 can have a different dynamic behavior on this type of filters. Nor is it realistic for a prescriber to want to test all possible substances and applications in real situations, as we have done in the various tests with the method on which the present invention is based (FIG. All the more so, according to devices such as those described in other documents, for example WO-01/43827 A1, the procedure would be too cumbersome to implement and would have no lasting operational character.

  Only a method such as that described in the present invention implemented on APRVAs equipped with facepieces as shown in the present invention through the embodiment examples and variant, preferred or not, could dispense a prescriber from the prior evaluation. conditions of use of such filters, while ensuring a safe use.

  However, this preliminary evaluation is feasible, in the absence of use of such APRVAs or complementarily in a general way, on a test bench (30), by a simulation method of extreme and average real exposure situations, with study of the mode operation, malfunction of such filters and its consequences, such as the teachings of the method underlying the present invention and the test examples described in FIGS. 3 & 10 show it.

  Fig. 12 shows an example of a retro-scan of the tested substance made on a filter after actual use. This retro-scan has been performed on a bench (30) 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 simulation method comparable exposure situations 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 complementary cross-check test phase on the same substance injected in the pure state, more generally, on any other substance (s) injected in pure form 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 rate of 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), set according to the average flow rate conditions. actual use of the filters an air humidifying device (32) having a water capacity, agitated by appropriate means (37) and reheated by appropriate means (38) to recreate, by continuous vaporization, if necessary, conditions comparable to those encountered in actual exposure situations. This humidifier makes it possible to test by simple comparison between, with and without, the effect of this humidity on the efficiency of the filters used.

  a buffer capacity (34) of suitable volume known and agitated by a suitable means (37), for example about 30 liters corresponding to the volume of air inhaled for about a minute by a person making a normal effort. A recording detector may be introduced or connected (36) for instantaneous concentration measurements at the filter inlet.

  devices (33) for introducing 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) making it possible to connect the filter to be tested to the capacity in the normal use direction (35.1) or in the backscatter direction (35.2).

  a device for connecting a recorder detector (36) after the filter.

  This preliminary evaluation is carried out according to a preferred method based on the experiment resulting from the process on which the present invention is based. In the preferred example described, such a method is adapted to reproduce at least the extreme and average phases of the actual conditions observed and measured in the field. This method takes into account an average time of about one hour generally accepted as ideal for the continuous wearing of a respiratory protection, this time being able to be increased to two hours under particularly satisfactory ergonomic conditions. At the end of this period, a rest period must be observed, during which time the filters can be replaced if necessary or controlled. . This method directly uses pure substances separately or in the form of mixtures This method introduces safety factors in several aspects, as well as the systematic verification of the reversibility of the adsorption to validate the possibility of treatment outside periods use. This method is generalizable to all types of filter and unassisted respiratory protection, such a method comprises at least one or more of the following phases: 1) Simulated maximum concentration: it is at least greater than 10 times the highest value of peak recorded in the field on a real exposure situation, during a given period usually quite short.

  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 times over a period of one hour to cover the majority of the cases encountered in Industrial Hygiene; first at the start of the test, followed by four or five more at regular intervals, 3) Simulated mean concentration: the simulated maximum concentration phases are set to give an equivalent average concentration, expressed for example over a period of fifteen minutes or eight hours of work, at least equal to twenty times the value of the actual average professional exposure measured over the same period.

  4) Minimum average concentration to be simulated: if a measured actual mean occupational exposure value, multiplied by twenty, is less than twenty times a Limit Value of the test substance, the maximum concentration phases will be set to be equivalent, for example over a period of fifteen minutes or eight hours of work, to an average concentration of at least twenty times such a Limit Value.

  5) Total duration of the simulation test: it is continued after the simulated maximum concentration phases, for example on the first hour, steps 2), 3) or 4), until appearance of the substance at the filter outlet (time output) and up to the recording of the maximum concentration peak (resolution time) 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, for example about one hour with high exposure. The air flow is maintained after the last introduction, for ten to fifteen minutes for example. The filter is then placed in backscatter position on the bench and the flow is maintained until the total purge of the filter substance.

  the end of purge time represents in these conditions the time during which an adsorption filter should be treated by back-scanning to be regenerated and that there is no more substance inside.

  in order to control such back-scanning, the quantity of substance found, especially when it is a low-boiling substance, must be comparable to the quantity of substance introduced. 7) The maximum continuous use period allowed : this is the exit time of the substance identified in 5), apart from any other actual measuring arrangement 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: it is the time 7), divided by a factor of which must take into account the maximum permissible period of availability 9), apart from any other regeneration treatment arrangement or special such filters, 9) The maximum period of provisioning allowed: the period after which a filter must be replaced whether it has been used or not, whether in the case of an individual endowment, or in the case of collective use, apart from any other regeneration treatment arrangements or special such filters .

  Fig. 14 shows examples of resolution curves of the test substance, performed 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 corresponding substance over the duration of the test at 10 to 100 times the TLV of such 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 corresponding to the 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 totally overlap those established in real exposure situations, particularly as regards the determination of the exit times of the substances.

Claims (41)

-47-CLAIMS   1. A method of ventilator-assisted respiratory protection, characterized in that at the outlet of a facial part made for this purpose, all or part of the air which is sent to it by a system is collected. respiratory assistance filtering said air, said total or partial return of air is brought back by a suitable air line to said respiratory assistance system and said total or partial air return is used for the measurement or control of one or more operating parameters of said method and of said respiratory system by the implementation of operations or means appropriate to the measurements or controls operated.   2. Method of ventilator-assisted respiratory protection according to claim 1, characterized in that a portion of said air filtered between the discharge of the assistance system and the suction of said system is continuously recirculated and rotated round. assistance and this recycling is used in controlled sequences of safety functions or replacement of filter or seal, without losing the benefit of the protection.   3. A method of ventilator-assisted respiratory protection, according to one of claims 1 or 2, characterized in that it comprises one or more of the following steps: a) selection of the air delivered to such a facial part to the output of the filters or the return of air, total or partial, of said facepiece, for the purpose of measuring or controlling various parameters; b) measuring, in parallel with or independently of said selection, the air pressure on the return air, total or partial, with respect to the pressure of the delivered air, and, in parallel with said selection , the flow rate on said total air return with respect to the flow of said delivered air; c) controlling and adjusting the actual positive pressure available in said facepiece, by acting at the level of the assisting means on said total air return; 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 calculating between said total air return and said delivered air, the total air leakage rate to the atmosphere of said facepiece; f) controlling and adjusting the flow rate of said delivered air so as to maintain a flow rate at least equal to the sum: [carrier air demand + mean air leak towards the outside + a fixed complementary value or advantageously proportional to said air demand of the wearer]; g) differential measurement of the concentration of substances on said delivered air, between an initial state observed at the start of operation of the filters and the evolution of this concentration during actual uses, in absolute value and / or drifting per unit time, to determine the instantaneous effectiveness and the duration of use; h) an alternative measurement, by means of said selection, of the concentrations of substances in said total or partial return of air, and said delivered air; i) differential calculation of the substance leak towards the inside of said facepiece, and therefore of the actual exposure to the substances with protection, independently and in addition to the substance breakdown concentration measured on said delivered air, and control of this leak; j) recycling continuously, in a round robin on the assistance fan, a portion of the filtered air for the purpose of performing controlled trip sequences.   k) verification or active control: of the sealing performed by a seal between a filter and its support, of the clamping pressure exerted on such a seal, of the manual perception of the end of normal clamping 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 detecting and isolating a filter and / or worn or defective seal in case of degraded operation of a device using at least two filters ; m) informing a carrier without being interfered with by his environment and without notifying him in his environment by the mere use of very low non-audible frequencies; n) information of a carrier on the only defects relating to the maintenance of his protection with request for simple and assisted action to preserve or restore this protection, supplemented by a local display and the recording of such information; o) optional and assisted replacement with filter (s) and / or filter seal (s) during an emergency, while retaining the benefit of protection; p) maintaining a sufficient protection, in this case a total return air, in case of total failure of the respiratory assistance using such facial parts; q) supplementing the respiratory protection with a skin protection using such a total air return at the outlet of such a device, to advantageously ventilate in a controlled manner a tight overcoating, partial or total, hood or combination type; r) cross-referencing of the determination of the actual efficiency of the filters as demonstrated in step g, by a method of simulations of extreme and average exposure situations, carried out on a bench and generalizable to respiratory protection without respiratory assistance.   4. Method according to claim 3, characterized in that step b). is carried out parallel to step a) which alternately selects, in a coupled manner for this step, and bypass a part of the air flows: E of said delivered air, at the same time as it closes the opening of said total return of air, allowing a flow measurement on the bypass of said delivered air and a measurement of the pressure on said total air return in pressure equilibrium with the inside of said facepiece, in relative value with respect to the atmospheric pressure , or as a differential value with respect to the pressure of said delivered air, or, E of said total air return, at the same time that it closes the opening of said delivered air, allowing a flow measurement on the bypass of said total return of air. air and a measurement of the pressure on said air delivered in pressure equilibrium with the output of an assistance means, in relative value with respect to the atmospheric pressure, or in differential value with respect to the press ion of said total air return, with respective calculation of the flow rates of said total air return and of said air delivered from the calibrated flow rate coefficients and memorized at construction between the flow rates measured on the main flows and such branches.   5. The method as claimed in claim 3, characterized in that step c) consists in regulating the actual pressure inside said facepiece at a programmed setpoint, starting from the measurement of the pressure carried out at the 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 diaphragmelclampet disposed on said total return of before venting said total air return; such a spring returns to a known mechanical fixed position, by default of current or control.   6. The method as claimed in claim 3, characterized in that step d) consists in determining differentially on said total air return the instantaneous and / or average air demand of a carrier, measured as being half of the the difference between the extreme and average flow rates recorded between the inspiration and the expiration phases.   7. The method as claimed in claim 3, characterized in that step e) consists in differentially comparing the averages of the flow measurements of said total air return and of said delivered air, in particular to determine the total air leak towards the outside. of such a facial piece.   8. Method according to claim 3, characterized in that step f) comprises acting on at least one of the parameters controlling the power of the assistance means to obtain a flow rate on said delivered air at least equal to the sum of the flow rates. : [carrier air demand + average air leak towards the outside + a complementary value, fixed or advantageously proportional to said carrier air demand].   9. The method of claim 3, characterized in that step g) consists in using and integrating suitable and interchangeable substance detectors in such a process, to incorporate in the operation of said detector measuring the concentration of substances on the said air at the output of the filters an optional reset of the measurement, programmable and triggered at a configurable time after the start of the respiratory assistance means or optionally after each replacement of the new or verified filters, and to apply a method of differential measurement, in absolute value and / or drift per unit time, between an initial state found corresponding to said zero measurement performed and any state likely to occur later during the use of such filters, to control the instantaneous effectiveness and / or the limit of duration of use.   10. Method according to claim 9, characterized in that step h) consists in measuring by means of said same substance detector, alternatively, the concentration of substances on said total or partial return of air at the outlet of said part. facial and substance concentration on said delivered air.   11. The method of claim 3, characterized in that step i) consists in calculating the difference in concentration of substances between said air return, total or partial, and said delivered air, independently and in addition to the concentration of substance breakdown measured on said delivered air, and to control the leakage substance inwardly of such a facepiece with respect to a programmed threshold, acting on the only flow control in the case of a partial return of air, or pressure and / or flow in the case of a total return air.   12. The method as claimed in claim 3, characterized in that step j) consists, in all the exemplary embodiment variants or other embodiments, involving at least two filters, to recycle filtered air in a permanent round , taken from the output of the respiratory assistance and also distributed on the output of each filter, more specifically returning between the output of each filter and a selection means of each filter disposed on the input of the common air assist all filters; such recycling being used in the controlled sequences of safety and assisted replacement filters or seals; in the exemplary embodiment variants or other embodiments comprising two filters, the selection means can be advantageously common to both filters is to be normally open position on both sides by default current or control.   13. The method of claim 3, characterized in that step k) consists in interposing between a filter and its clamping support, compliant or not in accordance with DIN 3182, a seal designed to perform the sealing functions, compression limiting, physical perception of the end of manual tightening, detection of the end of clamping and the normal presence of a filter on its support by an electrical contact established under a controlled atmosphere, internally to such a seal .   14. The method as claimed in claim 3, characterized in that step I) consists of using and analyzing all the measurements, calculated information, available states to identify from these measurements, information, states, the nature and location of a defect, determine the immediate action that will be required to a carrier to correct such a defect or, in the preferred embodiments and variants or other, involving at least two filters, to previously trigger a commanded sequence of safety achieving the selection and physical isolation, with confirmation of the isolated state, the worn or worn filter or the faulty seal, allowing a wearer to choose to leave a risk zone or to opt for the correction of a such defect by being assisted for the actions that will be requested, while retaining the benefit of protection.   15. Method according to claim 3, 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. air of said delivered air communicating with the inside of said facepiece, so that this vibration is directly perceptible on the face of a wearer, or transmitted directly by a vibrator placed closer to the skin contact of a porter, without soliciting the meaning of fouie.   16. The method of claim 3, characterized in that step n) implements a method of modulating such vibrations giving at least information and instructions useful for maintaining the protection of a wearer and simple actions that him are requested for this purpose, in general such a method uses a fixed low frequency non-audible modulated appropriately necessarily involving several levels of modulation, for example: the absence of vibration indicates normal operation and protection provided; vibration at a fixed frequency with long symmetrical continuous or discontinuous modulations indicates the detection of defects that a carrier can correct immediately: for example positive pressure defect and / or leakage rate to the detected atmosphere greater than a threshold, or presence of substances detected differentially on the total or partial return of air in the absence of a positive pressure defect or a leakage rate to the atmosphere; vibrations at a fixed frequency with intermittent long modulations, repeated at regular intervals, indicate to the wearer a partially degraded operation but remaining under control; - Vibrations at a fixed frequency, with a first series of fast and symmetrical modulations require the cessation of all activities, followed by a second series of asymmetrical modulations indicating the nature of the defect and the action requested from the wearer: for example detection poor clamping on a filter, or detection of presence of substance on the filter outlet in the absence of a poor clamping on a filter, defects on which it can act while preserving the benefit of the protection or leaving the zone of risk; vibrations at a fixed unmodulated and continuous frequency for at least one minute indicate to the wearer that his protection under conditions of sufficient security is no longer guaranteed, that he must press the facepiece on his face and leave the area of risk without precipitation; such a method comprises the complementary local display of this information for any person carrying out surveillance or assisting and rescuing a wearer in difficulty or unconscious, advantageously presented in the form of a chronogram modulated in the same way as the examples below. above, allowing this person to know exactly and in the same way the operating state of a wearer's protection and to be able to act on its protection; such a method comprises the additional registration in a memory area of this information and more generally any useful data and exploitable offline for the control and control of such a method.   17. The method of claim 3, characterized in that step o) consists, in the preferred embodiments and variants or others, involving at least two filters, deliberately trigger by the loosening of a maintained filter, detected as a fault, said commanded trip sequence which physically isolates the filter, with confirmation of the isolated state, and initiates an assisted replacement sequence of the filter (s) or joint (s) filters as appropriate; such a replacement sequence in an emergency situation being performed without losing the benefit of the protection or contaminate the concerned conduits which remain pressurized, doubly closed on both sides of said filtered air recycling, with a voluntarily limited leakage rate on a mechanical shutter valve directly in contact with the outside; such a replacement sequence comprising a delayed return to the normal operating mode after replacement, purging of the circuits before final tightening and checking of the states; such a replacement sequence not stopping and not controlling the respiratory assistance means.   18. A method according to claim 3, characterized in that step p) consists in adopting in said selection, coupled in normal operation, a control logic decoupled from the two shutter flaps corresponding to a normally closed state due to lack of current or command. Such a closure made on a small section is deemed sealed and thus prevents any return of substance from the atmosphere through said selection. Such control logic, supplemented by: the presence of a mechanical shutter valve on the output of each filter to the air assistance means, the default fixed voltage exerted by a spring on a diaphragm / valve disposed between said total air return and venting said total air return, maintains the protection in a conventional operating mode without assistance in the event of a power failure, without risk of accumulation of carbon dioxide in the air. inside a device or a facial part. The limited leakage on the mechanical shut-off valves required for the controlled trip sequences occurs outwardly on the filtered air side and is not a problem since the flow rate of such exhalation leakage is very low compared to expiratory discharge. Sufficient respiratory protection is thus maintained and allows to leave a risk area without precipitation.   19. The method of claim 3, characterized in that step q) consists in using such a total air return to supplement the respiratory protection with a skin protection using such a total air return, to advantageously ventilate controlled a tight overprotection, partial or total, hood or combination type.   20. A method according to claim 3, characterized in that according to an alternative embodiment of step b), carried out in parallel with step a), said air is alternately selected in a coupled manner for this step, said air delivered in deriving or all of said partial air return: E of said delivered air is selected at the same time that all of said partial air return is closed and its suction stopped, allowing a flow measurement on the bypass of said delivered air and a measurement pressure on said partial air return in pressure equilibrium with the inside of said facepiece, in relative value with respect to the atmospheric pressure, or as a differential value with respect to the pressure of said delivered air, or E said return partial air is selected in all and its suction activated at the same time as said delivered air is closed, allowing a confirmation of flow of said partial air return. r means for analyzing and measuring the pressure on said air delivered in pressure equilibrium with the output of a means of assistance relative to the atmospheric pressure.   21. The method of claim 3, characterized in that step r) implements a complementary method of cross-checking 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, is generalizable to all types of filter and unassisted respiratory protection, such a method comprises at least one or more of the following phases: 1) simulated maximum concentration: it is at least higher at 10 times the highest peak value recorded in a real work situation over a given period, usually of short duration.   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 times over a period of one hour to cover the majority of the cases encountered in Industrial Hygiene; first at the start of the test, followed by four or five others at regular intervals, 3) simulated mean concentration: the simulated maximum concentration phases are set to give an equivalent mean concentration, expressed for example over a period of fifteen minutes or eight hours of work, at least equal to twenty times the value of the actual average professional exposure measured over the same period.   4) minimum average concentration to be simulated: if a measured actual average occupational exposure value, multiplied by twenty, is less than twenty times a limit value of the test substance, the maximum concentration phases will be set to be equivalent, expressed for example over a period of fifteen minutes or eight hours of work, at an average concentration at least equal to twenty times such a limit value.   5) total duration of the simulation test: it is continued after the simulated maximum concentration phases, for example on the first hour and phases 2), 3) or 4), until appearance of the substance at the outlet of the filter ( output time) and up to the recording of the peak concentration maximum (resolution time) 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, for example about one hour with high exposure. The air flow is maintained after the last introduction, for ten to fifteen minutes for example. The filter is then placed in the back-scanning position on the bench and the flow rate is maintained until the total purging of the filter substance: the end of purge time represents in these conditions the time during which an adsorption filter should be treated by retro-scanning to be regenerated and that there is no more substance inside; to control such back-scanning the amount of substance found, especially when it is a low-boiling substance, must be comparable to the amount of substance introduced.   7) the maximum permissible continuous use time: it is equal to the exit time of the substance identified in 5), apart from any other actual measurement provision of this duration 8) the recommended cumulative use time: c ' is the time 7), divided by a safety factor which must take into account the maximum allowed provisioning period 9), apart from any other regeneration treatment arrangements or special such filters.   9) the maximum permissible period of availability: the period after which a filter must be replaced whether it has been used or not, whether in the case of an individual allocation, or in the case of a specific use. collective, apart from any other regeneration treatment arrangement or special such filters.   22. A respiratory protection device with assisted ventilation, comprising a facepiece (22), whose inlet (8) (22.3) is connected by a pipe (7) to a respiratory and filtration assistance system (1), the rigid part (22.0) of said shell-shaped face piece constitutes an air collecting device (22.4) towards its outlet, characterized in that it comprises a return air duct (9), by example constituted by a concentric pipe internal to the air supply pipe (9) or (9.2), or by a separate pipe, connecting the outlet (9) of said facepiece (22) to the respiratory assistance system (1) which comprises means (19), for example consisting of a centralized computer system comprising a microprocessor and for analyzing and / or measuring one or more characteristics of the returned air in order to control the operation of a such device.   23. Respiratory ventilation device with assisted ventilation, according to claim 22, characterized in that it comprises ducts (6) ensuring a continuous recycling in a round of a portion of the air between the discharge of the system. assistance (5) and aspiration of said assistance system, also distributed on particular points located between a filter selection means (4) and a shutter means (3) (3.10), allowing the control via the centralized system (19), functions of safety and / or replacement assisted filter or seal (3.1), without losing the benefit of the protection.   24. Device according to one of claims 22 or 23, characterized in that it comprises selection means (13) for: a) in a controlled manner, via the centralized system (19), the selection of the delivered air at the outlet of the filters (8), (8.1) to the facepiece (22), or the total (9), (9.1) or partial (9.2) air return of said facepiece, for measurement and / or control of various parameters, b) by default of control or current, to close the lines (8.1) and (9.1) towards the venting (17) 25. Apparatus according to claim 24, characterized in that it comprises pressure measuring means (12) [(12a) (12c)] (12b) for measuring, in parallel or independently with said selection of air ( 13), the air pressure on said air return, total (9.1) (9) or partial (9.2), with respect or independently to said delivered air (8. 1) (8).   - 59 - 26. Device according to any one of claims 22 to 25, characterized in that it is provided with control and regulation means (10) for controlling and adjusting the actual positive pressure available in said facepiece (22). ) in the case of said total air return, by acting on the means of assistance on said total air return through a device comprising at least: a valve diaphragm (10.1) on which a spring (10.2) exerts a variable pressure adjusted by a control means (10.3) controlled via the centralized system (19). 27. Device according to claim 24, characterized in that it comprises flow measurement means (14) and centralized processing means (19) for: measuring differentially or independently the air flow rates on the branches of said air delivered (8. 1) and said total air return (9.1), respectively calculating the flow rates of said delivered air (8), and of said total air return (9) from the stored flow rate ratio coefficients [( 8) 1 (8.1)] and [(9) 1 (9.1)], calibrated to construction on a fixed restriction (16), or conduit 17 or measuring means (14) acting as a restriction, or, assert the presence of a flow on said partial air return (9.2) to the analysis means (15).   28. Device according to claim 27, characterized in that it comprises means (19) for calculating differentially, in the case of said total air return (9.1) (9), the instant air demand and / or average of a carrier.   29. Device according to claim 27, characterized in that it comprises means (19) allowing, in the case of said total air return (9.1) (9), to differentially calculate the total air leakage rate d such a face piece (22) to the atmosphere, between the average flow rates measured on said delivered air and said total air return.   30. Device according to any one of claims 22 to 29, characterized in that it comprises means (19) for controlling and adjusting the flow rate of said delivered air (5), so as to obtain a flow rate on said delivered air at least equal to the sum of the flows (a + b + c) below: a. air demand of the wearer, b. average air leakage to the outside, c. complementary value fixed or advantageously proportional to said air demand of the carrier determined on said total air return. i0   31 Apparatus according to any one of claims 22 to 30, characterized in that it comprises means for detecting substances (15) for differentially measuring the concentration of substances on the delivered air, between an initial state noted at the time of in use of filters and the evolution of this concentration during actual uses, in absolute value and / or drift per unit of time, to determine the instantaneous efficiency and / or the limit of duration of use.   32. Device according to any one of claims 22 to 31, characterized in that it is provided with means (15) for measuring alternately, by means of said selection (13), the concentrations of substances in said return of total or partial air and said delivered air.   33. Apparatus according to any one of claims 22 to 32, characterized in that it is provided with means (19) for differentially calculating the substantially inward leakage of such a facepiece and to control it ( 5) (10), therefore to evaluate the actual exposure to substances with protection, independently and in addition to the substance breakdown concentration measured on said air delivered at the outlet of the filters.   34. Apparatus according to any one of claims 22 to 33, characterized in that it comprises means (3) for checking or actively controlling, the seal made by 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), the detection and confirmation of the normal presence of a filter on its support through such a seal and such an abutment, electrically conductive, 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); an appropriate device makes it possible to maintain such a seal in position: for example the plug (3.7a) allows such a hold by being depressed on a base firmly fixed in the pipe (3.6a), such a base is connected to an electrical circuit to through an impervious wall-pass (3.8); in such an example the plug (3.7b) is depressed floating on a connector (3.6b) connected to a flexible extensible wire itself connected to an electrical circuit through a sealed wall-pass (3.8); the extraction of such a seal is facilitated by a suitable device, for example an extraction ring (3.5), solidarily attached to a rigid portion of such a seal (3.2).   35. Device according to any one of claims 22 to 34, characterized in that it comprises means (19) for maintaining sufficient protection in case of degraded operation, on a single filter or on the remaining filters, after selection (13), detection (15) and insulation (4) of a filter and / or a seal (3.1) worn or defective.   36. Apparatus according to any one of claims 22 to 35, characterized in that it comprises information and / or alarm means (20), (20.2) for informing a carrier without being interfered with by his environment and without signaling it in its environment by using vibrations very low frequencies not audible.   37. Device according to any one of claims 22 to 36, characterized in that it is provided with means (19) generating such very low frequencies to inform a carrier (20) or (20.2) on defects only specific to the maintenance of its protection with simple and assisted action request to maintain or restore this protection, displaying (20.1) additionally in the form of a chronogram modulated in the same way the same information for any other person likely to assist a carrier, recording in real operating time in a memory area (21) any information or useful data exploitable offline for the control and control of such a method and such a device.   38. Device according to any one of claims 22 to 37, characterized in that it comprises means (4) [(3.) (3.1) (3.10)] (13) (15), controlled and / or controlled (19) allowing the optional and assisted replacement of one or more filter (s) and / or filter seal (s) in an emergency situation without losing the benefit of the protection.   39. Device according to any one of claims 22 to 38, characterized in that it comprises means [(10) (10.1) (10.2)] (13) on such a total air return and (3.10) ( 13) on said delivered air for maintaining sufficient protection in the case of said total air return and in case of complete failure of the respiratory assistance means (5) (1) using such facial parts (22).   40. Device according to any one of claims 22 to 39, characterized in that it comprises connecting means (11) for supplementing the respiratory protection by a skin protection using such a total return air collected on its output to advantageously ventilate in a controlled manner a tight overprotection, partial or total, hood or combination type.   41. Device for implementing the method according to claim 21, for cross-checking or determining the actual efficiency of the filters by a method of simulations of extreme exposure situations performed on a bench (30), from pure substances , generalizable to the respiratory protection in free ventilation, characterized in that it comprises at least one or more of the following devices: an air drying installation; an air flow control device (31), set according to the average flow conditions in actual use of the filters; an air humidifying device (32) having at least: a water capacity, agitated by appropriate means (37) and reheated by appropriate means (38) to re-create, by continuous vaporization, if necessary, air conditions; humidity comparable to those encountered in real exposure situations; this humidifier makes it possible to test by simple comparison between, with and without, the effect of this humidity on the efficiency of the filters used.   a buffer capacity (34) of a known volume of gas stirred by a suitable means (37), for example about 30 liters corresponding to the volume of air inhaled for about a minute by a person performing a low effort; for example, a recording detector is introduced or connected (36) for instantaneous concentration measurements at the inlet of the filter. devices (33) for introducing 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) making it possible to connect the filter to be tested to the capacity, in the normal use direction (35.1) or in the backscanning direction (35.2). a device for connecting a recording detector (36) after the filter.