How is acceptable indoor air quality defined per ASHRAE 62.1-2022?

• A. Air with zero contaminants regardless of occupant perception
• B. Air with no known contaminants at harmful concentrations and most occupants not dissatisfied
• C. Air that matches outdoors exactly
• D. Air without any odor

Answer: (B)

Acceptable indoor air quality means a level of air quality that protects health while also being acceptable to occupants in terms of perception. In ASHRAE 62.1-2022, this is defined by two key ideas: there are no known contaminants present at harmful concentrations, and the majority of occupants do not express dissatisfaction with the IAQ. This combination recognizes that you can control health risks through ventilation and filtration, but you don’t have to achieve a perfect, odor-free, or outdoors-mimicking environment.

Why this choice fits best: it directly ties IAQ to both objective health thresholds and subjective comfort, which is the essence of acceptable IAQ as defined by the standard. It acknowledges that trace contaminants can exist as long as they aren’t harmful, and it accepts some perceptual differences among occupants rather than requiring zero odor or an exact outdoor air match.

Why the other ideas aren’t right: aiming for zero contaminants is unrealistic in most built environments; some trace substances may be present without causing harm. Requiring indoor air to match outdoor air exactly isn’t a criterion in ASHRAE 62.1, since outdoor air can carry pollutants and odors that wouldn’t be acceptable indoors. Requiring no odor at all is an overly strict condition, since odors can be benign or tolerable and IAQ is evaluated on health and overall occupant satisfaction, not purely odor presence.