Earth's natural life support system provides the air we breathe, the water we drink, and other conditions that support life. The purpose of an Environmental Control and Life Support System (ECLSS) is to provide these needs when outside the Earth's biosphere. The functions of an ECLSS include: atmosphere revitalization; atmosphere control and supply; temperature and humidity control; water recovery and management; waste management; and fire detection and suppression. Other functions that may be considered part of the ECLSS include: food storage and preparation; plant growth facilities; radiation protection; external dust removal; thermally conditioned storage; and hyperbaric chambers and airlocks. The activities in this guide focus on water recovery and management.