Cartridges provide respiratory protection against gases and vapors by using sorbents to purify the inhaled air. The combo P100 particulate filter provides protection against aerosols by removing dusts, mists, fumes, fibers and other particuLatex; 99.97% minimum filter efficiency. The outer casings are made from a durable, lightweight material, and color coded for quick and easy identification. The combo cartridges are approved for use with both half mask series 7700 and 5500 along with the 7600 series full face pieces; 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 pack. 12 packs per case. Sold by the pack.