Under what condition is DCV permissible under 62.1?

• A. Regardless of IAQ
• B. IAQ remains within acceptable criteria
• C. Only in special spaces
• D. When occupancy is above a threshold

Answer: (B)

The main idea is that using DCV is allowed only if it keeps the indoor air quality (IAQ) within the levels defined as acceptable by ASHRAE 62.1. DCV relies on sensors (like CO2 or occupancy sensors) to reduce outdoor air delivery when spaces are less occupied, but it must never let IAQ degrade below the standard’s criteria. If IAQ stays within the acceptable range, DCV can save energy by lowering ventilation rates; if IAQ begins to exceed the allowable limits, the system must revert to the required minimum or increase outdoor air to restore acceptable IAQ. That’s why the best answer is that DCV is permissible when IAQ remains within acceptable criteria. The other options imply conditions tied to occupancy or arbitrary thresholds rather than the IAQ criterion specified by the standard.