This standard applies to commercial passenger air-carrier aircraft carrying 20 or more passengers and certified under Title 14 CFR Part 25. This standard considers chemical@ physical@ and biological contaminants as well as moisture@ temperature@ pressure@ and other factors that may affect air quality. Because this standard cannot take into account every variable@ especially those relating to safe operation of the aircraft@ the diversity of sources and types of contaminants in aircraft cabin air@ and the range of susceptibility in the population@ compliance with this standard will not necessarily ensure acceptable aircraft cabin air quality for everyone. PURPOSE This standard defines the requirements for air quality in air-carrier aircraft and specifies methods for measurement and testing in order to establish compliance with the standard.