Respirators that use filters or sorbents to remove harmful substances from the air.
A negative-pressure mask that uses filter cartridges to clean air for the user. The type of filter cartridge required varies based upon the expected contaminant.
A respirator which cleans contaminants from the air via cartridges and/or filters before the air is inspired by the wearer. These are the most commonly used respirators and are available in half-mask, full-face or powered units.