Acceptable Indoor Air Quality is defined as 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.

• A. Air with no known contaminants at harmful concentrations as determined by cognizant authorities and with 80% or more of exposed people not expressing dissatisfaction
• B. Air that is completely free of odors and contaminants
• C. Air that meets only odor criteria
• D. Air that has no viruses

Answer: (A)

Acceptable Indoor Air Quality is defined by two practical standards: there should be no known contaminants at harmful concentrations as determined by recognized authorities, and the majority of people exposed should not express dissatisfaction (80% or more). This frames IAQ as a balance between health-based limits and occupant perception, acknowledging that air can have odors or trace contaminants without posing a health hazard, and that aiming for a perfectly odor-free, contaminant-free environment is not always feasible.

The best option captures both parts: it states there are no known harmful contaminants per authorities and that at least 80% of exposed people do not express dissatisfaction. The other options miss essential aspects: one implies a completely odor- and contaminant-free environment, which is overly strict and not always achievable; another focuses only on odors, ignoring health-based contaminant limits; and another centers on viruses, which is a narrow focus and not the general IAQ criterion.