Carbon Dioxide (CO2) Removal Carbon Dioxide is produced in the body and expelled in human breath. The Carbon Dioxide Removal Assembly removes Carbon Dioxide from the air by using a material called “zeolite,” which acts as a molecular sieve. The molecules structure of the zeolite attracts and separates the CO2 molecules from the air as they pass through it. The Carbon Dioxide Removal Assembly depends upon the constant cleaning and reenergizing of the sorbent beds of zeolite. The waste CO2 is expelled into space through vents in the Space Station. The zeolite sieves require cold / dry air. The air must pass through the Temperature and Humidity Control Subsystem first. The Carbon Dioxide Vent Valve Assembly releases the collected Carbon Dioxide into space after cleaning of the zeolite beds. Computers and atmospheric sensors control this assembly. The gas release is very gradual so it won’t act as a rocket/propellant and change the Space Station’s orbit. Lithium Hydroxide (LiOH)-based canisters, which clean the air of CO2, are available for emergency use in case the Carbon Dioxide Removal Assembly fails. Each LiOH canister can last 14 days and can clean the air throughout the Space Station if the cabin air fans are working properly.