This proposed addendum removes the prefix 'ortho' from the term 'ortho-TCP' in all places (two) where it occurs in ASHRAE Standard 161. There are multiple isomers of Trichloropropane, and it is the intention of the standard to cover all of them, not just the ortho-TCP isomer. Standard 161 defines the requirements for air quality in air-carrier aircraft and specifies methods of measurement and testing for compliance with the standard.