electro - magnetic - energy absorbing materials are used to treat air filters , such as those used in association with electronic equipment thereby suppressing the transmission of electromagnetic interference therethrough . disclosed are processes and materials for applying emi - absorbing materials to air filters thereby improving emi - shielding effectiveness in an economically efficient manner . in one embodiment , an absorptive solution is prepared using an absorptive material and a binding agent . a heavy coating of absorbing solution applied to an air filter substrate , for example by dipping or spraying . excess absorbing material is subsequently removed and the absorbing material cured , such that the passage of air through the filter remains substantially unimpeded . the resulting absorptive air filter is then optionally treated with a flame retardant to meet a predetermined safety standard .