[ASHRAE Standard 62.1]:air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction.

[ASHRAE Standard 62.2]:air toward which a substantial majority of occupants express no dissatisfaction with respect to odour and sensory irritation and in which there are not likely to be contaminants at concentrations that are known to pose a health risk.

[ISO 16814:2008, 3.1]air in an occupied space toward which a substantial majority of occupants express no dissatisfaction and that is not likely to contain contaminants at concentrations leading to exposures that pose a significant health risk.