This document supplements and in some cases supersedes the recommendations presented in ARP 85D@ which refers to subsonic civil transports. The limits and design goals suggested in this report are as recognized by SAE Committee AC-9 and should not be interpreted as a definite specification. PURPOSE Due to the significant increase in speed and altitude of the supersonic transport above the subsonic jet transports (form Mach No. about 0.85 to 2.4-3.0@ altitude from 40@000 to 70@000 tt) and the decrease in the average time spent by the passengers in the aircraft (from about 5 to 2 hr)@ a careful review of the environmental control system from a safety and comfort point of view is needed.