This guideline applies to commercial passenger aircarrier aircraft carrying 20 or more passengers and certified under Title 14 CFR Part 25 (FAA 2008b). This guideline considers chemical@ physical@ and biological contaminants as well as@ but not limited to@ factors such as moisture@ temperature@ and pressure that may affect air quality. PURPOSE This guideline serves as a companion to ASHRAE Standard 161 (ASHRAE 2007) and provides supplemental information on air quality in air-carrier aircraft and on measurement and testing related to aircraft air quality.