Patent ID: 7278542

Claim:
A filtering medium based on a photocatalytic agent and activated carbon, comprising a permeable support in the form of a non-woven based on natural fibers and/or organic chemical fibers covered with a first activated carbon-based layer comprising at least 20% by weight of activated carbon, an exposed outer surface only of said activated carbon-based layer being directly covered by a separate second layer consisting of 5 to 40 g/m 2 of photocatalytic agent and a colloidal dispersion of SiO 2 , the colloidal dispersion of SiO 2 effectively binding particles of said photocalalytic agent to each other and to the first layer, said first layer comprising a fibrous cushion, wherein the mass of the activated carbon-based layer is between 10 and 300 g/m 2 and said activated carbon-based layer comprises a homogeneous mixture of either from 20 to 75% by weight of activated carbon fibers or from 70 to 90% by weight of activated carbon particles, whereby continuous desaturation of the activated carbon is achieved; and an outermost exposed surface consisting of an outer surface of said second layer.