Abstract: An active carbon material includes a gas permeable surface coating of particulate hydrophobic material which renders the active carbon waterproof while still permitting it to adsorb undesirable components. Preferably the hydrophobic material is polytetrafluoroethylene having a mean particle size of substantially a tenth of a micron. Active carbon is waterproofed by immersing it in an aqueous suspension of the hydrophobic material and then drying the active carbon to remove the water to leave the particulate coating of hydrophobic material on the outer surface of the active carbon.

Abstract: An activated carbon product such as a charcoal cloth or felt has, in addition to any activating material, a metal uniformly dispersed therein. The metal may be catalytic or bactericidal, and a particularly preferred product of the invention contains silver and is suitable for use as a surgical dressing. Such products can be produced by a conventional activation procedure using a mixture of halides, even if the further metal halide is substantially insoluble in the impregnation solution used for activation, by incorporating in the solution ammonia and a sequestering agent such as citric acid.

Abstract: An activated carbon product such as a charcoal cloth or felt has, in addition to any activating material, a metal uniformly dispersed therein. The metal may be catalytic or bactericidal, and a particularly preferred product of the invention contains silver and is suitable for use as a surgical dressing. Such products can be produced by a conventional activation procedure using a mixture of halides, even if the further metal halide is substantially insoluble in the impregnation solution used for activation, by incorporating in the solution ammonia and a sequestering agent such as citric acid.

Abstract: A gas adsorption filter consisting of a gas inlet, a gas outlet and one or more layers of charcoal cloth, the layers of which are arranged to lie substantially parallel to the direction of the gas flow between the gas inlet and the gas outlet.