GB2282329A

GB2282329A - Respiratory protective equipment

Info

Publication number: GB2282329A
Application number: GB9318636A
Authority: GB
Inventors: David Hugh Orr
Original assignee: TES BRETBY Ltd; Coal Industry Patents Ltd
Current assignee: TES BRETBY Ltd; Coal Industry Patents Ltd
Priority date: 1993-09-08
Filing date: 1993-09-08
Publication date: 1995-04-05
Also published as: GB9318636D0; AU7543694A; WO1995007115A1

Abstract

The equipment, which is of self-rescuer type, includes a canister 4, 6 and mouthpiece arrangement 8, the canister incorporating a low flow resistance catalyst 14, a prefilter 20 upstream thereof and a non-return inhalation valve 16 acting as a moisture barrier. The prefilter may be made from hopcalite and the catalyst may comprise a promoted tin (IV) oxide-supported precious metal catalyst carried on a honeycomb substrate. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO RESPIRATORY PROTECTIVE EOUIPMENT 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.

In our co-pending UK Patent Application No 93 02771.2 we describe an invention intended to overcome the disadvantages of the known filter self-rescuers whereby a catalyst of low flow resistance coupled with a moisture barrier were employed to achieve improvements in their efficacy and amenity.

It has now been found that certain gases can poison the catalyst and accordingly an object of the present invention is to overcome this problem.

According to the invention there is provided 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 mouthpiece arrangement, the canister incorporating a low flow resistance catalyst, a prefilter located upstream of the catalyst for protecting the catalyst, and a moisture barrier interposed between the catalyst and the mouthpiece arrangement.

Conveniently, the prefilter is made from hopcalite.

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 exhalation 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 which is diagrammatic cross sectional view.

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.

A prefilter 20 is located in the lower part 6 of the canister upstream of the catalyst 14 and is preferably made of hopcalite.

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 prefilter 20 and thence through the low flow, resistance catalyst wherefrom it passes to 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. The provision of the prefilter 20 protects the catalyst from poisoning from gases such as HCl and HCN.

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 CO2 and which exhibits low flow resistance.

Claims

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 mouthpiece arrangement, the canister incorporating a low flow resistance catalyst, a prefilter located upstream of the catalyst for protecting the catalyst, and a moisture barrier interposed between the catalyst and the mouthpiece arrangement.

2. Respiratory protective equipment according to Claim 1 in which the prefilter is made from hopcalite.

3. Respiratory protective equipment according to Claim 1 or 2 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.

4. Respiratory protective equipment according to any one of the preceding claims in which the catalyst is carried on a substrate which may be of honeycomb or other suitable formation.

5. Respiratory protective equipment according to any one of the preceding claims in which the moisture barrier is an inhalation valve.

6. Respiratory protective equipment according to Claim 5 in which the inhalation valve is mounted in the mouthpiece arrangement.

7. Respiratory protective equipment according to any one of the preceding claims in which the mouthpiece arrangement is conveniently dismountable from the canister.

8. Respiratory protective equipmment substantially as hereinbefore described with reference to the accompanying drawing.