How do I perform an airflow traverse for duct commissioning?

An airflow traverse divides the duct cross-section into equal-area rectangles (log-Tchebycheff method per ASHRAE Standard 111) and measures velocity at the center of each rectangle using a pitot tube connected to a manometer or electronic micro-manometer. For rectangular ducts, you need a minimum of 16–25 measurement points; for round ducts, traverse along two perpendicular diameters with 6–10 points per diameter. The velocity readings are averaged and multiplied by the duct area to compute airflow, and this traverse-derived airflow serves as the reference for calibrating permanently installed flow measuring stations. The traverse location must have straight duct runs of at least 7.5 hydraulic diameters upstream and 3 diameters downstream to ensure fully-developed flow; if this isn't possible, increase the number of measurement points by 50% and note the compromised location in the commissioning report.