A device consisting of a porous material (e.g., paper, felt or fiberglass) and an activated medium (e.g., activated charcoal) or both, used to remove particulate matter from the cooling water or air for welding equipment, from compressed air, or from the
breathing air for welders.
Alternatively, in radiography, a sheet or strips on edge (which may be oscillated) of absorptive material placed between the film and the object being radiographed to reduce blurring in the recorded film image caused by secondary and scattered radiation.