Filter mask
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A filter mask provides protection to the wearer from harmful airborne substances and usually covers only the mouth and nose. It limits the course of air so that it must flow through a filter which removes harmful dusts or toxic gases. Such masks range from cheaper, single-use, disposable types to reusable models with replaceable cartridges.
Because of their simple, passive design they are most commonly used for filtration of tiny suspended solid or liquid particles and often referred to as particulate masks. For this purpose, they usually employ a dense, fine natural or synthetic fiber mesh. To aid particulate filtration, the mesh is sometimes coated with substances that enhance the tendency of particulates to adhere to the fibers.
For gas filtration, mask cartridges are filled with activated carbon or certain resins that will absorb substances such as volatile organic compounds (VOCs), eliminating them from the air breathed. Though less effective for this purpose, and only suitable to the least demanding applications, single-use masks also sometimes employ embedded carbon granules in the fiber mesh. There are different cartridges for different compounds. When filter cartridges become saturated or particulate accumulation within them begins to restrict air flow, they must be changed.
