SCOPE: This Aerospace Recommended Practice (ARP) describes test equipment and methods used for testing closed cycle or semiclosed cycle breathing devices of short duration that are designed to operate with a high partial pressure of oxygen in the breathing circuit. It is intended to supplement ARP1109 and ARP1398 for applications involving closed cycle or semiclosed cycle breathing equipment which may be evaluated to the requirements of AS8031 and/or AS8047. Purpose: This ARP recommends performance requirements for test equipment used to simulate human respiration in the testing of aviation protective breathing equipment (PBE). This ARP does not@ however@ preclude the need for human testing.