How is the measurement for air flow characteristics, as shown in NFPA 72 design documentation, obtained?

How is the measurement for air flow characteristics, as shown in NFPA 72 design documentation, obtained?

• A. From each pipe sampling port to the detector
• B. Across the entire sampling installation
• C. At changes in direction or branches
• D. From the control panel to the detector

Answer: (A)

Air flow characteristics for aspirating fire alarm systems are verified by checking the flow along each sampling path from its specific port to the detector. This per-port approach is necessary because the network of tubing and fittings creates different resistance in every branch, so the actual flow at each port can vary. By measuring from every sampling port to the detector, you confirm that each port delivers the intended air flow and the detector’s sensitivity is maintained across the entire system. Measuring only the overall installation, or just a single segment such as changes in direction or a path from the panel to the detector, would miss imbalances and could leave some ports under- or over-sampled.

Air flow characteristics for aspirating fire alarm systems are verified by checking the flow along each sampling path from its specific port to the detector. This per-port approach is necessary because the network of tubing and fittings creates different resistance in every branch, so the actual flow at each port can vary. By measuring from every sampling port to the detector, you confirm that each port delivers the intended air flow and the detector’s sensitivity is maintained across the entire system. Measuring only the overall installation, or just a single segment such as changes in direction or a path from the panel to the detector, would miss imbalances and could leave some ports under- or over-sampled.