Abstract: A chemical canister for use in a respirator has opposed openings, one for connection to a mouthpiece and the other for connection to the rest of the respirator. The canister contains a carbon dioxide removing and oxygen liberating chemical, and there also is a chemical which, upon being heated, will liberate nitrogen to mix with the oxygen liberated in the canister.

Abstract: A supplementary filter housing is provided in one side with an opening for receiving the inlet end of a respirator filter attached to a facepiece. Inside this housing there is a perforated partition between the filter-receiving opening and a portion of the housing that extends laterally away from that opening, whereby to separate the housing into first and second chambers, the second chamber being in the laterally extending portion of the housing and having a perforated outer wall for admission of air. Disposed in the second chamber is a removable filter member that is in the path of air flowing through that chamber from its perforated wall to the perforated partition. The second chamber also has an access opening for insertion and removal of the filter member, which is formed from a material that will dry the air inhaled through it.