GB2275612A - Improvements in or relating to respiratory protective equipment - Google Patents

Abstract

Respiratory protective equipment of the self-rescuer type includes a mouth piece arrangement 8 and a canister 6 incorporating a low flow resistance catalyst 14 with a moisture barrier 16 interposed between the catalyst and the mouth piece arrangement. The catalyst comprises a promoted tin IV oxide-supported precious metal catalyst wherein the metal is platinum, palladium, rhodium, iridium or ruthenium and the promoter is one or more metals of group 1B, 3B, 7B and 8 of the chemical periodic table other than precious metal. The catalyst may be carried on a substrate of honeycomb etc.. The mouthpiece may be dismounted from the canister. A heat exchanger 10 cools the filtered air. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO RESPIRATORY PROTECTIVE EQUIPMENT This invention concerns improvements in or relating to respiratory protective equipment of the type known as a filter self-rescuer.

Such equipment is commonly used in mines and is of a type which does not provide oxygen, but which removes noxious gases such as carbon monoxide from the ambient atmosphere before inhalation. It is a statutory requirement for anyone going underground in coal mines in the United Kingdom to carry a filter self-rescuer. The conventional filter self-rescuer incorporates a catalyst known as 'Hopcalite' which oxidises CO to Co2 with an attendant evolution of heat. Additionally, the catalyst becomes poisoned with moisture and accordingly a drier has to be employed. The wearer therefore has to breathe hot, dry air and whilst there is no inherent danger therefrom, individual wearers might well experience discomfort and in practice could ill-advisedly remove the associated face mask with potentially fatal results. Furthermore, such conventional self-rescuers tend to have a high gas flow resistance, for example 8-13 millibar, because of the depth of catalyst bed and the presence of a drier, again occasioning in some wearers laboured breathing with concomitant discomfort and possible distress. The working life of the equipment is approximately 90 minutes which can be a relatively short time span in the circumstances of an underground accident involving contamination of the mine atmosphere with carbon monoxide.

An object of the invention is to provide respiratory protective equipment of the self-rescuer type devoid of the disadvantages of the conventional equipment while affording greater user comfort and efficacy of operation with higher amenity.

According to the invention a respiratory protective equipment of the self-rescuer type includes a canister through which in use a wearer inhales and exhales through the agency of a mouth piece arrangement, the canister incorporating a low flow resistance catalyst and including a moisture barrier interposed between the catalyst and the mouthpiece arrangement.

Advantageously. the catalyst comprises a promoted tin IV oxide-supported precious metal catalyst, the precious metal being platinum, palladium, rhodium, iridium or ruthenium, and the promoter being one or more metals of group lb, 3b, 7b and 8 of the Periodic Table other than precious metal.

The catalyst employed in the equipment of the present invention may conveniently be carried on a substrate which may be of honeycomb or other suitable formation.

Since the catalyst has a very low flow resistance, the wearer finds considerably greater comfort when using the self-rescuer. However, because of such low resistance, the ratio of the resistance to exahalation through the normal path may approximate to or exceed that of the reverse flow path through the catalyst: but for the moisture barrier exhaled gases could flow back through the catalyst saturating and contaminating the same with moisture thereby rendering the catalyst ineffective. The presence of the moisture barrier thus prevents reverse flow of exhaled gases through the catalyst.

The moisture barrier may conveniently be an inhalation valve which for convenience can be mounted in the mouthpiece arrangement. The mouthpiece arrangement is conveniently dismountable from the canister.

Since the flow resistance of the catalyst is low, the comfort of the wearer is improved in comparison with conventional self-rescuers, thereby assisting in ensuring that during actual use in a hostile environment, the wearer is content to keep the self-rescuer on.

By way of example only, one embodiment of respiratory protective equipment of the filter self-rescuer type according to the invention is described below with reference to the accompanying drawings in which: Figure 1 is a diagrammatic sectional view of the filter self rescuer in its inhalation operational mode; and Figure 2 is a diagrammatic sectional view of the filter self rescuer in its exhalation mode.

Referring to the drawings, respiratory protective equipment is shown as a filter self rescuer 1 including a body 2 having a top part 4 and a lower part 6. The top part 4 includes a mouthpiece 8 through which in operation a user inhales and exhales. A heat exchanger 10 is provided in the top part in association with the mouthpiece 8 in order to cool inhaled filtered air.

The top part 4 also has a non-return exhalation valve 12 through which in use exhaled gases may flow unidirectionally out of the rescuer.

The lower part 6 is in the form of canister for a low flow resistance catalyst 14 which may be a promoted tin IV oxide-supported precious metal catalyst, the precious metal being platinum, palladium, rhodium, iridium or ruthenium, and the promoter being one or more metals of group lb, 3b, 7b and 8 of the Periodic Table other than precious metal. The catalyst may conveniently be supported on a honeycomb structure or some other suitable formation.

Interposed between the top and the lower parts 4, 6 is a moisture barrier 16 which may in the form of a non-return inhalation valve whereby the flow therethrough is unidirectional to the mouthpiece, reverse flow being prevented.

In operation, the filter self rescuer 1 is worn by a user in an atmospherically hostile environment to remove harmful components in the ambient atmosphere. Figure 1 shows the path taken by air inhaled by the user, namely through the low flow resistance catalyst 14 and the inhalation valve 16 and thence into the mouthpiece to the user, there being no outflow through the exhalation valve 12.

During exhalation by the user, gases pass through the mouthpiece and exit through the valve 12, the inhalation valve 16 preventing reverse flow into the catalyst and ensuring isolation of the catalyst from the contaminating moisture laden exhalation gases.

No drier is needed with the catalyst of the present invention and thus the size of the canister housing the catalyst can be significantly shallower than that required for conventional self-rescuers. The canister is thus less cumbersome and accordingly the amenity in terms of carrying the self-rescuer is enhanced.

It has been found that the potential operational life of the catalyst in the canister is 8 to 10 hours thereby giving vastly improved security and greater confidence for the wearer using the equipment in hostile conditions.

It is to be understood that the catalyst may be of any suitable kind which performs the task of oxidising CO to C02 and which exhibits low flow resistance.

Claims (6)

1. Respiratory protective equipment of the self-rescuer type including a canister through which in use a wearer inhales and exhales through the agency of a mouth piece arrangement, the canister incorporating a low flow resistance catalyst and including a moisture barrier interposed between the catalyst and the mouthpiece arrangement.

2. Equipment according to Claim 1 in which the catalyst comprises a promoted tin IV oxide-supported precious metal catalyst, the precious metal being platinum, palladium, rhodium, iridium or ruthenium, and the promoter being one or more metals of group ib, 3b, 7b and 8 of the Periodic Table other than precious metal.

3. Equipment according to Claim 1 or 2 in which the catalyst employed is carried on a substrate of honeycomb or other suitable formation.

4. Equipment according to any one of the preceding claims in which the moisture barrier is an inhalation valve mounted in the mouth piece arrangement.

5. Equipment according to any one of the preceding claims in which the mouth piece arrangement is dismountable from the canister.

6. Respiratory protective equipment substantially as hereinbefore described with reference to the drawings.