What does occupant exposures refer to in IAQ design?

• A. The concentration and duration of exposure to contaminants that occupants experience in the space.
• B. The rate of outdoor air changes per hour.
• C. The mass of contaminants generated by equipment.
• D. The total number of occupants in a space over a day.

Answer: (C)

Occupant exposures refer to the actual dose occupants receive, meaning the concentration of contaminants in the breathing zone multiplied by the time they are exposed. In IAQ design we focus on what people truly inhale over their occupancy period, which emerges from how contaminants are generated, diluted, and removed by the system. The mass of contaminants generated by equipment is a source term—it tells you how much contaminant enters the space but not how much occupants actually experience. The rate of outdoor air changes per hour is a ventilation metric that affects dilution of contaminants, but it isn’t the exposure itself. The total number of occupants over a day influences potential exposure opportunities, but it doesn’t define the exposure concentration or duration.