42 CFR § 84.194
Filters used with chemical cartridges; location; replacement
June 11, 2020
(a) Particulate matter filters used in conjunction with a chemical cartridge shall be located on the inlet side of the cartridge.
(b) Filters shall be incorporated in or firmly attached to the cartridge and each filter assembly shall, where applicable, be designed to permit its easy removal from and replacement on the cartridge.