North N75002 Acid Gas Cartridge 2/pk for North 7700 Series Respirator North offers an extensive line of gas and vapor cartridges and particulate filters to satisfy numerous industrial applications. One line of cartridges and filters will simplify your inventory. Air-purifying respirators with cartridges provide respiratory protection against gases and vapors by using sorbents to purify the inhaled air. Cartridges with filters also remove dusts, fibers, and other particles. All North cartridges and filters are NIOSH approved with North air-purifying half masks and full facepiece respirators.