The lunar module environmental control subsystem provides life support functions, active cooling for the heat loads, and water and oxygen. Featured designs include brushless d-c motors, water sublimators, water-gas centrifugal separators, and cold rail electronics cooling. Testing proceeded incrementally from component development through flight vehicle vacuum chamber demonstrations. Major developments required were the water sublimators, water-gas centrifugal separators, oxygen pressure regulators, and iodine-water compatibility with the system. The flight records of the lunar module environmental control subsystem have been satisfactory.