The Space Shuttles life support system automatically supplies air and water.
	An atmosphere like the earths is maintained in the crew compartment. Atmospheric pressure is the same as standard sca level conditions. The atmosphere consist of 79% nitrogen and 21% oxygen, again very close to what the astronauts left on earth. In an emergency, cabin pressure is reduced. Carbon dioxide is a waste product and must not be allowed to build up in the cabin. Therefore, canisters filled with lithium hydroxide and activated charcoal remove carbon dioxide and odors from the cabins air. Fans circulate the air around the cabin and through the canisters. Carbon dioxide reacts with lithium hydroxide to produce lithium carbonate and water vapor.
	Two canisters are used at a time. With four people abroad, an individual canister lasts 24 hours. They are changed alternately; that is one changed everu 12 hours. As with other chores, responsibility for changing the carbon dioxide absorbers is assigned to a different of the crew each day.
	TheThe cabins atmosphere is controlled from panels. The are awitches to select whith soursce of oxygen you want to use. The oxygen supply is carried in the form of a super cold liquid. Each liquid oxygen tank has heaters which vaporize some of the super cold liquid.
	If it gets too warm or too cold, one can adjust the cabin temperature using the cabin temp switch. Below this switch are controls for the fans that circulate air through lithium hydroxide canisters.
	Electrical power for the Orbiter is generated by fuel cells. Oxygen and hydrogen are chemically combined in the celle to produce electricity. There is an important by product from this reaction-water. About 3 kilograms of water is created every hour.