3Mª High Efficiency Formaldehyde Gray Cartridge attaches to the motor blower and filters through that air is supplied to the headgear. Cartridge is used with the 3M belt-mounted and vehicle-mounted powered air purifying respirator systems and provides protection against formaldehyde. It is used in the field of assembly, machine operations and is recommended to use in industries like mining, oil and gas, sold as 6 per case.