For outdoor air quantities to air handlers over 2,000 cfm, how often should measurements be taken?

• A. Every 3 years
• B. Every 5 years
• C. Every 10 years
• D. Every year

Answer: (B)

Measuring outdoor air delivery is about ensuring the system is meeting the design ventilation rate while keeping maintenance practical. For air handlers with a sizable outdoor-air portion, the values don’t typically drift rapidly, and the costs and disruption of frequent checks become less justifiable. A mid-range maintenance cadence hits a sweet spot: it’s frequent enough to catch any gradual drift in damper positions or sensor calibration before it causes IAQ or energy issues, but not so frequent that the effort and expense outweigh the benefit.

Choosing this middle-ground interval reflects the idea that large outdoor-air quantities don’t require annual verification, yet they shouldn’t be left unchecked for very long. The other timeframes are either too aggressive for routine verification on these systems or too lax to reliably catch drift over time. So, the best-fit approach is to schedule measurements on a mid-range cycle, which matches common practice for larger outdoor-air portions and balances accuracy with practicality.