What is the maximum air transport time allowed for air sampling-type systems?

• A. 60 seconds
• B. 120 seconds
• C. 180 seconds
• D. 300 seconds

Answer: (B)

Air sampling-type systems rely on drawing ambient air through a sampling line to a detector. That creates a transport delay between what’s happening in the environment and what the sensor reads. To keep readings meaningful and alarms timely, there’s an upper limit on how long that air can take to reach the detector. The typical standard uses a moderate maximum—long enough to be practical to implement, but short enough to avoid storing stale air. If the delay were longer, the system could miss rapid changes in conditions; if it were much shorter, it would be overly stringent and hard to guarantee in all installations. So the middle option reflects the commonly accepted maximum transport time for these systems.