Which statement best describes occupant exposures in IAQ context?

• A. It considers the concentration and duration of exposure to contaminants occupants experience.
• B. It considers only the number of occupants.
• C. It considers only outdoor air quality.
• D. It is irrelevant to indoor air quality.

Answer: (A)

In IAQ, occupant exposure is about the dose occupants receive from indoor contaminants, which depends on how concentrated the contaminants are in the breathing zone and how long people are exposed to them. This means both the concentration of pollutants and the duration of exposure drive potential health effects, since dose increases with higher concentration and longer time (and also with activity level and breathing rate). So the best description is that occupant exposure takes into account both how much of a contaminant is present indoors and how long people are exposed to it. The other ideas—counting people alone, focusing only on outdoor air quality, or deeming IAQ irrelevant—don't capture the actual inhaled dose people experience.