What does outside air control with demand-controlled ventilation generally accomplish?

• A. Ventilation rate adjusts based on occupancy or air quality.
• B. Ventilation rate is fixed at 15%.
• C. Ventilation only operates when the building is unoccupied.
• D. Ventilation rate is determined by thermostat setting alone.

Answer: (A)

Demand-controlled ventilation uses sensors to adjust outdoor airflow in real time based on how many people are in a space or how poor the air quality is, rather than sticking to a fixed ventilation rate. This means the system increases ventilation when occupancy grows or air quality deteriorates, and reduces it when spaces are lightly occupied or air quality is good, all while still meeting the minimum outside air required by the standards. This approach saves energy by avoiding unnecessary outdoor air while maintaining acceptable IAQ.

The other ideas don’t fit because outside air isn’t kept at a fixed percent, such as 15%, and the system doesn’t only run when the building is unoccupied. Also, outdoor air decisions aren’t made by the thermostat alone; DCV relies on dedicated sensors (like CO2 or occupancy sensors) and a control strategy that links ventilation rate to actual demand.