Which statement about indoor air quality calculations under standard guidelines is true?

• A. It accounts for contaminants originating from both the occupants and the space
• B. It ignores contaminants from occupants
• C. It uses only floor area to determine ventilation
• D. It uses only the number of occupants to determine ventilation

Answer: (A)

Indoor air quality calculations are about ensuring the air is diluted enough to keep contaminant levels within acceptable limits. A true statement is that these calculations account for contaminants originating from both occupants and the space. People generate CO2, moisture, and various VOCs through breathing, sweating, and activities, while the building environment contributes emissions from materials, furnishings, cleaning products, and equipment. The required ventilation rate is determined by considering these sources in addition to outdoor air quality, so the system brings in enough fresh air to dilute both occupant-related and space-related contaminants.

If you only used floor area as the basis, you’d miss how many people are present and how much they emit. If you used only the number of occupants, you’d miss background emissions from materials and equipment. Ignoring occupants altogether would overlook a major driver of indoor contaminant levels.