GB1581905A

GB1581905A - Disinfection of material medical appliances or closed rooms

Info

Publication number: GB1581905A
Application number: GB18935/78A
Authority: GB
Original assignee: Institut Pasteur de Lille
Current assignee: Institut Pasteur de Lille
Priority date: 1977-05-12
Filing date: 1978-05-11
Publication date: 1980-12-31
Also published as: IT7849309A0; OA05963A; DE2820595A1; BR7803112A; IT1156733B

Description

(54) IMPROVEMENTS IN AND RELATING TO THE DISINFECTION OF MATERIAL, MEDICAL APPLIANCES OR CLOSED ROOMS (71) We, INSTITUT PASTEUR PRO DUCTION, of 36 Rue du Docteur Roux, 75725 Paris Cedex 15, France, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates to a process and an apparatus for disinfection by sequentially evaporating an aqueous solution of an antiseptic gas and an aqueous solution of a neutralizing gas, wherein these solutions are exposed to a current of air, the material or apparatus to be disinfected being subjected to the air charged with the vapours and gas released by the said solutions. The invention likewise relates to an antiseptic gas inaqueous solution for the performance of this process.

While not limited thereto in its utility, the following description will refer more particularly to the disinfection of artificial respirators, owing to the dangers to which patients are exposed as a result of unsatisfactory disinfection or antiseptic vapours inadequately neutralized and eliminated. The fact is that the disinfection of these appliances is an essential requirement, as any gases or polluted air will be introduced direct into the respiratory tracts of the patients. Accidents due to contamination are therefore frequent, very serious and often fatal.

It is important not only that the disinfection should be total but also that any irritant effect due to residues should be completely eliminated. Residues, when consisting of deposits, are also liable to impede the operation of certain essential components, such as clacks and valves and to result in the evitable dangers thus caused.

It is known to volatilize formol solutions for disinfection purposes. The disinfection operation with formol is known to be carried out with the use of apparatus comprising a formol evaporator, consisting of a tank in which a formolized solution is heated to about 50"C and more by an electrical resistance. The solution is introduced by gravity into the tank from - a storage cistern connected thereto. When the solution has flowed down into the tank the storage cistern is closed by means of a tight plug. The tank is connected to a compressed air inlet of which the rate of delivery is regulated with a flow meter.

When the apparatus is started up the air penetrates into the tank and is conveyed direct onto the surface of the formol solution, causing the latter to be stirred up and thus assisting the evaporation of the formaldehyde. The air charged with formaldehyde circulates in the internal circuits of the appliances to be disinfected. As this gas emitted is highly irritant it has to be neutralized after the disinfection, and the medium hitherto used most frequently is ammonia gas. A second evaporator, similar to that described, is employed for this purpose, but without heating the ammonia solution, as this gas is highly volatile. Thereafter a final rinsing phase with compressed air is started.

These three phases, i.e. formolization, neutralization and rinsing, are programmed automatically by timing devices which cause magnetic valves to open and close in accordance with the time allocated to each cycle.

The problem which remained to be solved was that of the complete elimination of the condensations. Up to the present they have not been reduced to a sufficient extent, despite the use of the most carefully designed condensers. The fact is that any little drops of water containing formol and left in the conduits of the apparatus are still present after the neutralization and contain hexamethylene tetramine and ammonia, which prove very dangerous irritants for the patient's respiratory tracts. Furthermore, at the moment when the neutralization is effected a chemical reaction takes place between the drops of formol and the ammonia gas, resulting in the creation of a more or less considerable quantity of hexamethylene tetramine, which takes the form of a white powder. Now the formation of this powder must be prevented, as it is liable to deposit itself in the tubular circuits and various components of the apparatus, such as clacks, valves etc., and impede their operation. Interference of this kind in the functioning of medical equipment is quite unacceptable, as such appliances are required to be highly reliable.

Now it has been found that the evaporation of formol, which, it must be remembered, always take the form of a solution consisting inter alia of a certain quantity of water and of formic aldehyde, is accompanied by an amount of the said water, generally in the form of steam, and that this condenses in the apparatus to be sterilized.

This condensed water, in its turn, retains a comparatively considerable quantity of formol, leading to the drawbacks mentioned above. If, therefore, the condensations of formol and more particularly of the formic aldehyde are to be avoided, steps must first of all be taken to avoid the condensations of water in the appliances which it is required to sterilize. It should be noted that the condensations of steam may give rise to an additional problem, i.e. that of the oxidation of the metal surfaces of the apparatus to be treated.

One of the causes of the faulty operation due to condensations is an air delivery rate in excess of the permissible maximum. The fact is that these disinfection appliances are designed for a maximum delivery of 8-10 litres of air per minute, and if this rate is exceeded condensations occur despite the presence of the condensers which have been proposed as a remedy. The reason for this limit, where the output of air is concerned, resides in the construction of the evaporators. If the delivery of air in contact with the solution in the evaporator is too great, it results in a fractionated evaporation of the formol solution. In other words, the constituents of the latter are not evaporated simultaneously and in constant proportions.

This fractionated evaporation first of all causes abundant evaporation of the water, leading to an increase in the concentration proportion of formic aldehyde, which is left behind, in the form of hydrates, in the solution. The initial evaporation of the water not only increases the risk of condensation of water in the apparatus to be disinfected, with the resulting drawbacks, but also results in the danger of a loss of antiseptic product, for if the formic aldehyde concentration exceeds 50% this aldehyde will polymerize and form a considerable deposit in the evaporator.

According to the invention there is provided a process for disinfection by sequentially evaporating an aqueous solution of an antiseptic gas and an aqueous solution of a neutralizing gas, wherein these solutions are exposed to a current of air, the material or apparatus to be disinfected being subjected to the air charged with the aqueous vapours and antiseptic gas of the said solutions, comprising the steps of soaking a liquid absorbing element with the aqueous solution of antiseptic gas product in a hermetic enclosure, causing a flow of air to pass through said enclosure, directing the flow of air onto the said element in order to charge it with water vapour and with antiseptic gas and subsequently subjecting said material or apparatus to the air charged with neutralizing gas, the flow of air in said enclosure being automatically interrupted before the exhausting of said solutions.

In one advantageous embodiment of the invention the air is preheated and compressed before being conveyed into the enclosure.

The process can be advantageously used for the simultaneous disinfection of the external and internal circuits of one or more units of apparatus, such as an artificial respirator.

This assembly provides a considerable saving of time and thus of expense and above all a very high degree of safety, particularly for patients using artificial respirators and other material. The high air delivery rates also enable any material, such as beds and bedding, clothing, trolleys etc., to be treated in these disinfection chambers.

There is also provided a disinfection apparatus comprising one or more evaporators of antiseptic gas and/or neutralizing gas in solution and conduits serving to convey air through the evaporators and convey the vapours and gas issued of the said solutions into a collector pipe connected to an enclosure or an apparatus to be disinfected, each evaporator consisting of a hermetic enclosure containing an absorptive element of a porous substance immersed in a liquid to be evaporated, means for admitting air into the evaporator, means for guiding it over the surface of the said element, means for preventing the air from coming in contact with the surface of the liquid, a conduit for the supply of liquids to the apparatus, said conduit being designed to maintain a constant level of liquid in the said enclosure, a further conduit for the evacuation of air and of liquid vapours.

A metering system based on a timing device recording the periods of time of the different ventilating sequences on the soaked element enables the emission of disinfectant and neutralizing products to be monitored.

The timing device is set to the maximum time which can be allowed to lapse before the apparatus is thereby automatically switched off and an alarm signal generated, the latter being required well in advance of the moment when the active product of the antiseptic solution will be exhausted. The apparatus cannot be re-started until the charge has been renewed.

This control can in another way be effected by the aid of either a liquid level detector reaching near the bottom of the enclosure or a moisture detector, consisting of two feelers in contact with the soaked element. This probe will be set to ensure that it will switch off the apparatus and cause the alarm signal to be emitted before a preselected humidity threshold has been passed, and here again the apparatus cannot be re-stated before the renewal of the charge.

This control system ensures the maximum degree of safety, as the use of an exhausted antiseptic solution is highly dangerous, owing to the way in which it renders the appliance ineffective. Forgetfulness or negligence of the operator's part may subject patients to serious infection, and the present invention enables this risk of accident to be reduced.

The process covered by the present invention enables a flow of gas or air to be propelled at a low or high pressure, particularly in certain artificial respirators operating on compressed air and requiring a pressure of 3 bars. When no compressed air is available a compressor can be used for taking the gases from the disinfection chamber and propelling them at the recommended pressure into these respirators or other equipment. It is also possible to use an annular blowing machine, which has the property of heating and drying the air, thus enabling air heaters in most cases to be dispensed with.

The process provides a means of nonfractionated evaporation, not necessitating the heating of the solution, an operation which constituted one more of the causes of excessive production of steam in the old process. The air can be insufflated into the tank of the evaporator at ambient temperature or slightly heated up.

Screens can be provided at the base of the evaporators; their concave surface is situated above the level of the solution, in order to isolate it from the ventilation, while the air comes into contact with the absorptive element, impregnated with an antiseptic gas in aqueous solution. The air in contact with a film of the solution from which it extracts the gas, in accordance with Henry's Law, thus becomes charged with water vapour and with the antiseptic gas which will then no longer become concentrated in the solution.

The process also provides a means of ensuring an even rate of evaporation and prevents an excessive charge of water vapour from occurring, the constituents of the antiseptic solution being evaporated simultaneously and in a constant proportion, in the form of a completely stable invisible water vapour and gas. It should be noted that with the process covered by this patent application the use of condensers can be eliminated altogether. Experiments have shown that by using vessels 0 the same dimensions as those employed in the old types of apparatus mentioned farther back but providing them with an absorptive element, in the manner described, it is possible to obtain delivery rates up to 100 instead of 10 litres per minute but still without any condensation being observable. In one advantageous version of the invention the element designed to absorb the antiseptic gas solution consists of a cylindrical element having a number of folds, in order to present the maximum possible area to the air in circulation. This results in very considerable delivery rates without the formation of tiny drops in any part of the apparatus. The evaporation is directly proportional to the volume of air in contact with the impregnated porous substance and in inverse proportion to its hygrometric degree, this being the reason why it is of advantage to dehydrate the air beforehand, if necessary, under certain climatic conditions, when the hygrometric degree is a very high one.

Up to the present the aqueous solution of the antiseptic gas used for the disinfection has been a solution of formol, the neutralizing gas solution adopted being ammonia.

Now it is a known fact that certain derivatives of isothiazolinone have good bactericidal properties. In particular, it is known that the mixture of 5 chloro - 2 - methyl - 4 isothiazoline - 3 - one and 2 methyl - 4 isothiazoline - 3 - one, also supplied under the trade name of "KATHON 886", is very effective, in stabilized aqueous solution, for numerous disinfection processes, particularly those carried out by spraying.

The applicant has discovered that the use of vapours of these products, contrary to all expectations, is more advantageous than the use of sprayed solutions. The problem arising, however, is that of vaporization, as it is very difficult to emit these products simply by heating, since they generally turn brown towards 1800C and actually decompose if a temperature of 250"C is exceeded. It is also known that the evaporation of a solution by heating or boiling does not enable homogeneous and simultaneous emission of all these components to be obtained.

However, the process according to the present invention enables the above problems to be overcome and according to a further aspect of this invention the antiseptic product consists of a derivative of isothiazolinone.

Further features and characteristics will become apparent from the following detailed description, given by way of an example and by reference to the attached drawings, in which: Figure 1 is a diagram of a disinfection apparatus in accordance with the present invention.

Figure 2, 3 and 4 show the details of an evaporator.

Figure 5 is a schematic diagram showing how a disinfection apparatus in accordance with the present invention is used in conjunction with a disinfection chamber.

Figure 5a shows a detail from Figure 5.

Figure 1 shows an evaporator 6 for the antiseptic product and an ammonia evaporator 7 designed in accordance with the present invention. The evaporator 6 consists essentially of a tank 8 combined with a cover 9, to which it is hermetically connected by means of a joint 10 and a tightening device 11. The tank 8 contains an element 12 made of a porous substance, and absorbing the antiseptic solution in which it is immersed, as well as a guard or screen 13, which prevents direct contact between the air and the solution, so that no disproportionate evaporation of water will occur.

This antiseptic product in the evaporator 6 advantageously consists of a mixture of 5 chloro 2 methyl 4 isothiazoline- 3 - one and 2 methyl - 4 - isothiazoline - 3 - one.

Highly satisfactory results have already been obtained, for example, with "KATHON 886" suitably diluted in the following proportions: - 8% mother solution, i.e. 80 ml of product and 920 ml of distilled water.

Accordingly the following description will refer more particularly, by way of example, to the use of "KATHON 886".

In certain cases the percentage of the mother solution can be reduced or increased, e.g. in the presence of particularly resistant germs, until the bacteriological controls give satisfactory results. The vaporization of the solution of derivatives of isothiazolinone, i.e.

its passage from the liquid to the gaseous state, enables these bactericides to penetrate tiniest interstices, porous substances, mattresses and hollow ceilings.

This ensures homogenous distribution through the premises thus treated, so that only a small quantity of active product is required and the risks of toxicity are reduced, the maximum degree of effectiveness in the treatment nevertheless being obtained.

The "KATHON" solution contained in a storage vessel 15 is fed through a conduit 14 by which it is in communication with the interior of the tank 8 via the cover 9. The liquid contained in the tank 8 saturates the element 12 from its base upwards. The storage vessel 15 contains a flask of "KATHON" 16 placed upside down on the end of the conduit 14. The latter is preferably bevelled so that it will automatically pierce the destructible capsule of the flask 16 when the latter is placed on the conduit 14 to enable the solution to flow out without any risk of discomfort to the operator from the antiseptic gases resulting from the introduction of this charge before the storage vessel 15 is sealed with a plug 17.

The absorptive element 12 preferably takes the form of a cylindrical element with folds (see also Figures 2 and 3) into which air is conveyed through a conduit 18. The ammonia evaporator 7 is identically similar to the "KATHON" evaporator 6, these elements being given the same reference numbers as the corresponding elements of the said evaporator 6 but with an added index figure to distinguish them from these latter.

The ammonia evaporator will therefore not be described in detail.

According to the present invention the air conveyed into the evaporator 6 and 7 at different moments, through one common conduit 24 and valves, 20 and 20', may be provided either by a source of compressed air or by a blower. The reference number 25 denotes a union to be connected to a source of compressed air (not shown). The rate of air delivery is regulated by means of a knob 26 and indicated by a flowmeter 27. The air may also come from a blower 28 but then passes through a filter 29. This circuit can be automatically connected to the conduit 24 just in front of an air heater of which the temperature is adjustable by means of a thermostat (not shown). The operation of conveying the non-treated air into the collector 23 is effected by means of a magnetic valve 30, its rate of delivery being regulated by a knob 31. It is also possible to provide an air heater (not shown) at the outlet from the collector 23 in order to ensure more rapid drying of the internal circuits and also to heat the antiseptic gases, if this is considered desirable.

A variant which can be applied both to the "KATHON" evaporators and to the ammonia evaporators is shown in Figure 4.

This is characterized by the fact that the saturation is undergone by the upper part of the element 12. This soaking action then takes place at a quicker rate, rendering the apparatus immediately ready for use. The conduit 14 guides the solution onto a disc 36, and this solution runs off the periphery of the disc onto the upper part of the element.

The reference numbers 37 and 38 denote the feelers of an electronic moisture detector in contact with the soaked element, one of these feelers being earthed and the other connected to the supply of electric current and to the electronic measuring device (not shown).

A description will now be given of the preparatory operations for the apparatus shown in Figure 1. After the absorptive elements 12 and 12' have been inserted into the evaporators 6 and 7, the plugs 17 and 17' are unscrewed in order to enable the doses of "KATHON" and ammonia to be introduced from the flasks 16 and 16' respectively.

When this operation has been completed the plugs 17 and 17' are immediately replaced, the solutions of "KATHON" and ammonia then flowing into the evaporators. A constant level is maintained at the base of the elements, this level being determined by the distance of the end of the conduits 14 and 14' from the base of the tanks.

After the union 25 has been connected to a compressed air source or to the ventilating device of the annular blower 28, the programmer (not shown) and the air delivery will be set as required. The said programmer may consist of timing devices or of an electronic device serving to set up the different operations at the required times. This setting process may be carried out in the following manner: Drying: 10 minutes, for the drying of the conduits by the circulation of hot air or at ambient temperature.

Disinfection: 1 hour, for treatment with "KATHON".

Pre-rinsing: 10 minutes, to eliminate the "KATHON" with sterile hot air or at ambient temperature.

Neutralization: 15 minutes, for this neutralization by ammonia gas.

Final rinsing: 1 hour, for rinsing with sterile air in order to eliminate the residual gases in their entirety.

At the start of the first cycle the programmer (not shown) causes the magnetic valve 30 to open and the hot air is conveyed into the collector pipe 23 and into the internal circuits of the artificial respirators in order to dry them and prevent the antiseptic product from depositing itself on damp places and causing the trouble of the kind described farther back.

In the second cycle the magnetic valve 30 is closed while the valves 20 and 22 are open.

The hot air or at ambient temperature is forced through the conduit 24 and the con du.t 18 into the "KATHON" evaporator 6.

The air charged with "KATHON" is evacuated from the evaporator via the conduit 21 and conveyed through the collector pipe 23 into the internal circuits of the respirators.

During the third cycle the magnetic valves 20 and 2 are closed while the valve 30 is once again open and the "KATHON" gases are expelled from the pipe 23 and from the internal circuits of the respirators by the circulation of sterile air. The magnetic valve 30 is then re-closed while the valves 20' and 33 are opened, the air is forced through the conduit 24 and the conduit 18' into the ammonia evaporator 7 and the ammonia gas is caused to pass through the conduit 21' and the collector pipe 23 into the circuits of the respirator.

During the fifth and last cycle the magnetic valves 20' and 33 are closed while the valve 30 is once again open, this phase constituting the final rinsing with sterile air, and at the end of this cycle the respirator is immediately ready for further use without any danger, as the apparatus no longer contains any residual irritant gases.

Figure 5 provides a schematic diagram of a complete installation consisting of the disinfection chamber 40 connected to its disinfection apparatus 41, as shown in Figure 1. This assembly can be used for the external disinfection of any material such as beds, bedding, and clothing as well as any other material of which inaccessible internal circuits have to be disinfected at the same time.

The chamber 40 is provided with a tight door 42 and connected to an air admission conduit 43 fitted with a filter 44. This filter is in communication with the chamber 40 via an air admission clack 46 shown in detail in Figure 5a. This clack 46 comprises calibrated orifices 47 of which the purpose is to slow down the diffusion of the gases into the filter in order to disinfect it and maintain an effective concentration of these gases in the chamber.

An extraction ventilator 48 associated with a valve 49 is provided for the purpose of extracting the gases or vapours from the disinfection chamber 40. The clack 49 comprises a check valve set to open only after a certain pressure has been exceeded, this pressure being selected to ensure a "preferential" diffusion of the gases through the filter, at the same time maintaining an effective concentration of the antiseptic gases in the chamber.

The disinfection apparatus 41, designed to produce the vapour and antiseptic gas, is connected by a conduit 61 and a union 62 to the disinfection chamber 40. The disinfection apparatus 41 comprises a control panel 64 fitted with a programmer and an air delivery regulating knob 65. The equipment contained inside the disinfection apparatus 41 consists essentially of an evaporator 66 serving to produce the "KATHON" gases and an evaporator 67 for the production of the ammonia gas. The admission of air to the evaporators can be effected either by means of compressed air passing through a union 68 or by the aid of a blower 69 and from a manual valve via a conduit 71 which is in communication with the air admission conduit 43 via a connection 72. The blower equipment 69 is also connected to the disinfection chamber 40 via a conduit 73 and a manual valve 74.

Figure 5 shows by way of illustration an artificial respirator 75 situated inside the dis infection chamber 40. The air admission orifice 76 communicating with the internal circuit of the respirator is connected by means of a flexible tube 77 to the air supply conduit for the antiseptic gases 78. The respirator 75 is also connected to current intake by an electric wire 80.

A description will first be given of the disinfection process for the internal and external parts of the artificial respirators 75 by means of the installation shown in Figure.

After the disinfection apparatus 41 has been prepared its union 68 is connected to a compressed air intake. The programmer is set in accordance with the description given farther back by reference to Figure 1. For the disinfection of the internal circuits and external components in the disinfection chamber 40, the electric wire 80 is connected to a current intake 79 and the union 78 is connected to the air admission orifice 76 of the respirator by means of the flexible tube 77. After the manual valves 79 and 74 have been closed the respirator is set in operation, the door 42 closed and knob 65 set to a delivery rate, for example, of 30 litres/minute.

In the "KATHON" treatment the gases pass through the internal circuits of the artificial respirator 75 and re-emerge therefrom, distributing themselves in the disinfection chamber ,thus disinfecting the external components. The "KATHON" gases also enter the filter 44 via the calibrated holes 47 of the valve 46, the said filter being thereby disinfected automatically. The calibrated valve of the clack 49 maintains a certain concentration of gas in the disinfection chamber 40 in order to disinfect the external components. The closing force of the clack 49 is sufficient to ensure complete disinfection of the filter as well, enabling the surplus vapours to escape mainly through the said filter, via the calibrated orifices of the clack 47.

This "KATHON" treatment is both very rapid and very efficient, since it ensures complete disinfection of the respirator 75, starting from its interior and continuing to the air admission 43, via the filter 44.

When the "KATHON" treatment phase is brought to a stop by the programmer 64 the extraction ventilator 48 is automatically set in operation and the "KATHON" vapours are evacuated both from the internal circuits of the respirator 75 and from the interior of the disinfection chamber 40 by the combined action of the ventilator 48 and of the compressed air admitted through the union 68.

The end of this "KATHON" vapour evacuation phase is likewise determined by the programmer 64. The programmer 64 simultaneously sets up the ammonia evaporation phase for the neutralization of the antiseptic gases. The ammonia gas follows exactly the same traject as that followed previously by the "KATHON" gases, and at the end of the neutralization cycle effected by the ammonia the programme 64 sets up the compressed air rinsing operation and the extraction of the gases from the chamber, the disinfection process thus being terminated.

The artificial respirator 75 is then immediately ready for use.

In order to simplify the foregoing description only one single respirator has been referred to, but where a number of appliances have to be disinfected simultaneously a container for the gases is provided inside the chamber and comprises a number of connecting conduits, the air delivery rate being increased in accordance with the number of appliances to be treated.

As already mentioned, objects of various kinds can be disinfected in the chamber 40, such as beds, bedding etc. A disinfection process of this kind can also be carried out by operating the disinfection apparatus 41 by the aid of the blower unit 69. In this case the disinfection apparatus 41 will be prepared and regulated as described in the foregoing.

The flexi matic operation, which greatly facilitates the use of the apparatus.

It should be noted that the fact that the filter 44 mounted in the air admission circuit 43 is automatically disinfected during the disinfection process taking place in the chamber 40 constitutes a major advantage of the invention and ensures an unsurpassed degree of safety. The use of the blower enables high delivery rates to be obtained and the range of application of the apparatus to be extended to certain other premises than large disinfection chambers. A further reason is that different operating pressures can be adopted and antiseptic gases can be conveyed over considerable distances through conduits of very moderate cross sections, particularly in ventilating shafts.

Figure 5 shows a neutralization evaporator 51, of different shape but of similar design to those used for the apparatus 41, while the item marked 52 is a container fed with solution by a storage cistern 55 and a conduit 56, the tap 81 enabling the conduit to be shut off when the solution has to be replenished. The storage vessel is connected u hermetically, enabling a constant level to be maintained, this level depending on the distance of the end of the conduit from the base of the container. The item marked 53 is a perforated support on which rests a flat element of absorptive material, particularly blotting paper, its two folded ends being immersed in the solution. the air is guided over the surface of the element 53 by a deflector 57. The passage of the air over the surface assists the evaporation of the gases. This makes it possible to neutralize the antiseptic gases on their emergence from the chamber. A filter (not shown) can with advantage be fitted to the outlet 58, thus assisting a more intimate exchange of the gases, in order to neutralize them, or enabling the bacteria to be destroyed when an antiseptic is used.

The programming of the apparatus enables the most exacting safety requirements to be met. In particular, the setting adapted will be that which ensures that there will at no time be any concentration liable to cause a risk of explosion or bursting.

It should also be emphasized that the gases used in the process are always nescent and not re-cycled, resulting in exceptional efficiency.

The use of derivatives of isothiazolinone enables the deposit and other drawbacks resulting from the use of formol to be avoided, particularly the polymerization of the product and its adhesion to cold parts of the apparatus.

Where it is necessary to disinfect premises which may contain material but which are not occupied by personnel, about 15-20 mil of "KATHON", diluted in the same proportions as above, per cubic metre of air, e.g. 15 ml x 100 = 1'500 ml in the case of one hundred cubic metres, will be evaporated in apparatus designed for high delivery rates and with the use of the same evaporation process.

The proportion of 15-20 ml per m3 can be reduced for hermetically closed rooms or increased for those incompletely closed, the latter being liable to cause considerable air renewal rates, which have to be taken into account.

A period of contact of 3 to 6 hours for the vapour thus and gas emitted in the room will in most cases suffice for total disinfection, known as terminal disinfection, a valuable advantage by comparison with other disinfection processes, particularly those carried out with the use of formol, necessitating about 10 hours for the same result to be obtained. The action of the bactericidal product is assisted by a suitable proportion of moisture. Good results, for example, are obtained with a hygrometric ratio of 65". If it is less, 10-15% distilled water will be added to the quantity of solution dictated by the cubic capacity of the premises to be treated, and this will result in a more favourable hygrometric ratio for the same temperature.

The derivatives of isothiazolinone, highly diluted, as indicated farther back, and evaporated by the process described, do not have a very irritant effect, so that the neutralization will be optional, and in most cases it will be sufficient for the premises treated to be satisfactorily ventilated or for the respirators, incubators or other appliances to be copiously rinsed with sterile air after the disinfection process.

In order to obviate any accident if somebody enters the premises while the disinfection operation is in process, for example, the bactericidal solution can be given an addition, as described before, of a small quantity of tracer, such formic aldehyde solution, of which the irritant and very characteristic odour will indicate the absence of the ventilation, and this also applies to the disinfection of respirators or other appliances in the disinfection chambers.

In such cases it will frequently be necessary to carry out the neutralization and then the ventilation before entering the premises or re-using the apparatus. The small quantity of formol solution added to the solution described in the foregoing can only be of benefit, as certain bacteria may be sensitive to possible synergy. The air on enclosed premises and in ventilator shafts can be rendered healthy by this same evaporation process, with the use of suitable apparatus started up at regular intervals and operating with far more highly diluted solutions, and essential oils.

For the disinfection of apparatus in an enclosure in which the gases have to be extracted and expelled to the outside, they can be first of all caused to pass through a neutralization evaporator operating with ammonia. This solution may also be replaced by a purifying material consisting of ammonium salt (carbonate, acetate or others, easy to dissociate).

This process for causing antiseptic gases, particularly derivatives of isothiazolinone to be carried along by water vapour is highly reliable and enables excellent results to be obtained without causing disadvantageous condensations when the pulsation of farm air at a low temperature is adopted. For the disinfection of containers which have been used for deceased persons before transfer to the coffins, the temperature will be increased in such a way as to obtain a saturating vapour which will condense on the internal walls, which are thus washed with the bactericidal solution produced automatically and trickling down over the said walls. The specially designed apparatus can be introduced into the actual containers concerned or operate in a closed circuit as indicated above with reference to Figure 5.

Finally, it should be noted that the invention is not limited to the use of formol or derivatives of isothiazolinone but is equally suitable for other autiseptic products. Similarly, the ammonia could be replaced by other neutralizing products without thereby departing from the scope of the invention.

IHAT WE CLAIM IS: 1. A process for disinfection by sequentially evaporating an aqueous solution of an antiseptic gas and an aqueous solution of a neutralizing gas, wherein these solutions are exposed to a current of air, the material or apparatus to be disinfected being subjected to the air charged with the aqueous vapours and antiseptic gas of the said solutions, comprising the steps of soaking a liquid absorbing element with the aqueous solution of antiseptic gas product in a hermetic enclosure, causing a flow of air to pass through said enclosure, directing the flow of air onto the said element in order to charge it with water vapour and with antiseptic gas and subsequently subjecting said material or apparatus to the air charged with neutralizing gas, the flow of air in said enclosure being automatically interrupted before the exhausting of said solutions.

2. A process as claimed in claim 1, wherein the air is preheated.

3. A process as claimed in claim 1 or 2, wherein the air is compressed.

4. A process as claimed in claim 1, 2 or 3, wherein the air admitted into the enclosure is prevented from coming in contact with the antiseptic solution contained therein.

5. A process as claimed in claim 1 or 2, wherein air is admitted by suction through a filter which is exposed to the antiseptic vapours in the course of the disinfection process.

6. A process as claimed in any one of claims 1 to 5, comprising sequentially the steps of drying the conduits by passing a current of hot dry air though them, disinfect by evaporation of a solution of antiseptic gas, passing the antiseptic gas through the places to be disinfected, evacuating the antiseptic gas by the passage of a current of hot dry air, evaporating the neutralizing gas and passing the neutralizing gas through the places treated, in order to neutralize the residues of antiseptic gas, and rinsing all the conduits by means of a current of hot dry air.

7. A disinfection apparatus suitable for carrying out the method of claim 1, comprising evaporators of antiseptic and neutralizing gas in aqueous solution and conduits serving to convey air through the evaporators and convey the vapours and the gases released by the said solutions into a collector pipe connected to an enclosure or an apparatus to be disinfected, each evaporator consisting of a hermetic enclosure containing an absorptive element of a porous substance immersed in a liquid to be evaporated, means for admitting air into the evaporator, means for guiding it over the surface of the said element, means for preventing the air from coming in contact with the surface of the liquid, a conduit for the supply of liquids to the apparatus, said conduit being further designed to maintain a constant level of liquid in the said enclosure, and a further conduit for the evacuation of air, of water vapours, and gases.

8. An apparatus as claimed in claim 7, further comprising timing means which may be set to the maximum time which can be allowed to lapse before the solutions are exhausted and before the apparatus is automatically switched off and an alarm signal generated, whereby the apparatus, if switched off in this way, cannot be re-started until the solutions have been renewed.

9. An apparatus as claimed in claim 7, further comprising an electrical level detector for switching off the apparatus and generating an alarm signal before the solutions are exhausted.

10. An apparatus as claimed in claim 7, further comprising a moisture detector for detecting the moisture of said absorptive element and for switching of the apparatus and generating an alarm signal before the solution are exhausted.

11. An apparatus as claimed in claim 7, wherein the absorptive element consists of a hollow cylinder of star-shaped cross section.

12. An apparatus as claimed in claim 7, wherein the means for preventing the air from coming in contact with the liquid consist of a screen positioned coaxially in the hollow part at the base of the absorptive element.

13. An apparatus as claimed in any one of claims 7 to 12, further comprising a dis

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. extracted and expelled to the outside, they can be first of all caused to pass through a neutralization evaporator operating with ammonia. This solution may also be replaced by a purifying material consisting of ammonium salt (carbonate, acetate or others, easy to dissociate). This process for causing antiseptic gases, particularly derivatives of isothiazolinone to be carried along by water vapour is highly reliable and enables excellent results to be obtained without causing disadvantageous condensations when the pulsation of farm air at a low temperature is adopted. For the disinfection of containers which have been used for deceased persons before transfer to the coffins, the temperature will be increased in such a way as to obtain a saturating vapour which will condense on the internal walls, which are thus washed with the bactericidal solution produced automatically and trickling down over the said walls. The specially designed apparatus can be introduced into the actual containers concerned or operate in a closed circuit as indicated above with reference to Figure 5. Finally, it should be noted that the invention is not limited to the use of formol or derivatives of isothiazolinone but is equally suitable for other autiseptic products. Similarly, the ammonia could be replaced by other neutralizing products without thereby departing from the scope of the invention. IHAT WE CLAIM IS:

1. A process for disinfection by sequentially evaporating an aqueous solution of an antiseptic gas and an aqueous solution of a neutralizing gas, wherein these solutions are exposed to a current of air, the material or apparatus to be disinfected being subjected to the air charged with the aqueous vapours and antiseptic gas of the said solutions, comprising the steps of soaking a liquid absorbing element with the aqueous solution of antiseptic gas product in a hermetic enclosure, causing a flow of air to pass through said enclosure, directing the flow of air onto the said element in order to charge it with water vapour and with antiseptic gas and subsequently subjecting said material or apparatus to the air charged with neutralizing gas, the flow of air in said enclosure being automatically interrupted before the exhausting of said solutions.

2. A process as claimed in claim 1, wherein the air is preheated.

3. A process as claimed in claim 1 or 2, wherein the air is compressed.

tributing disc mounted in the enclosure above the said absorptive element and below the conduit for the supply of liquids to the apparatus, the diameter of the said disc being approximately equal to the average diameter of the absorptive element.

14. An apparatus as claimed in claim 7, wherein each evaporator is connected to a source of compressed air and to an air heater.

15. An apparatus as claimed in claim 7, wherein each evaporator is connected to an air admission conduit via an air filter, a blower unit and an air heater.

16. An apparatus as claimed in claim 15, wherein the air filter is in communication with the collector pipe.

17. An apparatus as claimed in claim 7, wherein the air and vapour conduits upstream and downstream from the evaporators are fitted with magnetic valves and wherein a programmer is provided which is associated with a timing device for setting up the different phases of a disinfection operation, particuLarly the opening and the closure of the said magnetic valves.

18. A disinfection installation comprising a disinfection apparatus as claimed in any one of claims 7 to 17 wherein the disinfection apparatus is associated with a disinfection chamber provided with a hermetic door and with a ventilator for the evacuation of the gases, the said chamber being connected in series with the air admission conduit between the air filter and the blower unit and also connected to the collector pipe of the disinfection apparatus.

19. An installation as claimed in claim 18, further comprising a check valve mounted between the evacuation ventilator and the disinfection chamber and provided with a valve calibrated to open at a predetermined pressure.

20. An installation as claimed in claim 18, further comprising a flexible tube designed to be connected to a union of the collector pipe inside the disinfection chamber and also to internal circuits of an appliance which is to be disinfected and which has been placed in the disinfection chamber, so that both the internal and the external parts of this appliance are disin fected in succession.

21. An installation as claimed in claim 18 or 19, further comprising an evaporator for neutralizing products, mounted downstream from the ventilator.

22. A process as claimed in any of claims 1 to 6 wherein the antiseptic product is a derivative of isothiazolinone.

23. A process as claimed in claim 22, said antiseptic product consisting of a mixture of 5 chloro - 2 - methyl - 4 isothiazoline - 3 - one and 2 methyl-4 isolthiazoline - 3 - one.

24. A process as claimed in claim 22 or 23, wherein the antiseptic product is mixed with a tracer comprising a certain quantity of formic aldehyde solution.

25. A process substantially as hereinbe fore described with reference to and as illus trated in either of the accompanying draw ings.

26. An apparatus substantially as hereinbefore described with reference to and as illustrated in either of the accompanying drawings.

27. An installation substantially as hereinbefore described with reference to and as illustrated in either of the accompanying drawings.

For the Applicants,