GB516268A - Improvements in or relating to gas mask filters and the like - Google Patents

Abstract

516,268. Respiratory filters. VOVES, F., FIEDLER, B., and ECKHARDT, V. July 22, 1938, No. 21849. [Class 81 (ii)] The effective body of a filter insert or filling for protection against noxious gases, vapours and solids is formed from a felted mass comprising a homogeneous mixture of a fibrous material, e.g., cellulosic material produced from wood in paper mills, and substances capable of effecting absorption and adsorptive removal of the noxious materials, e.g., potash and active charcoal respectively. The material may have a moisture content of say up to 20 per cent. or more. For producing the felted mass, the fibrous substance, active carbon and a solution of potash are mixed, and the thin paste is poured on to a sieve to form a slab. As shown (Fig. 5), the filter insert for a gas mask filter may comprise a series of rings h of the material joined alternately around the inner and outer peripheries by rings j<1>, j and spaced by spaces k, there being no central aperture in the end layer h<1>. The insert is held in the case by supports m, n. The bottom o of the canister is removable. Another form of insert consists of a number of chambers for impure air communicating with the outer atmosphere at one end of the filter, such chambers alternating with chambers for purified air communicating directly with the interior of the mask at the other end of the filter. Fig. 3 shows a known form of filter consisting of a layer f of porous material mixed with a chemical absorptive material, and a filter body g consisting of a mixture of active carbon and cellulose. Other known forms are illustrated.