Cartridges provide respiratory protection against gases and vapors by using sorbents to purify the inhaled air. Cartridges without particulate filters do not remove dust, fibers and other particles. North offers wide selection of cartridges to provide respiratory protection against a range of industrial air contaminants. The outer casings are made from a durable, lightweight material, and color coded for quick and easy identification. The cartridges are approved for use with both half mask series 7700 and 5500 along with the 7600 series full facepieces; you only need one inventory of cartridges and filters. All cartridges are NIOSH approved, meet 42 CFR 84 requirements, when used with North air-purifying respirators. 2 cartridges per package. 18 packages per case. Sold by the package.