GB480507A - Improvements relating to filters and purifiers employed for conditioning air, for example for respiration, or other gas by freeing it from poisonous gases and other injurious or undesired constitutents - Google Patents

Abstract

In air or gas purifying apparatus, particularly <PICT:0480507/III/1> individual or collective filters for removing noxious constituents from respired gases, the exhaust of the filter materials is indicated by passing the gases, during or after passage through the filter materials, through electrically insulating material enclosed between two plates connected in a circuit including a signal, the insulating materials being capable of absorbing one or more of the gas constituents, thereby being rendered ineffective as insulators, whereupon the signal is operated. The plates may be separated by the insulating materials alone or such materials may be coated on one or both plates enclosing conducting material or on the material itself. Where the filter is for carbon-disulphide, acetone, essence of turpentine, ether, carbon tetrachloride, chloropicrin, yperite, cellulose solvents and the like an insulating material soluble in the constituents may be employed, e.g. paraffin or benzoic acid, and such material may be coated or sublimed on to the plates or a mass of conducting material, such as active carbon, between them, or the conducting material may be dipped into the fused insulating material. The plates may be spring-pressed as described in Specification 450,825, [Group VI]. As shown a pair of plates 11, connected to one pole of a battery 17 in a circuit including an electric signal 16 enclose a plate 12 connected to the other pole, the spaces between the plates being filled with indicator insulating materials 13, 14, for different classes of noxious constituents. The signal current may be used to operate a relay circuit including a signal or an auxiliary motor employed to replace the exhausted filter by a fresh one.