A chemical filter assembly mounted in a breather opening in a housing for a magnetic storage device or other device to permit pressure equalization with the surrounding environment comprises at least one filter medium for removing particulate matter, and a unitary filter medium of a fabric of activated carbon fibers that is impregnated with a chemical that in combination with the carbon provides protection against both organic and inorganic gaseous or vapor pollutants, said fibers having a pore size small enough prevent significant penetration by aqueous solutions so that during impregnation the pores will not become clogged with the chemical.