QAV Calculator

Exterior capture hood estimate: Q = 3600 × V × (10X² + A) for unflanged; flanged estimated at 75% of unflanged airflow, with X in metres. V represents capture velocity at the source, not duct transport velocity. For preliminary sizing only; cross-draughts, hood shape and commissioning can change requirements.

Uses 1 CFM = 1.6990108 m³/h (more precise than the spreadsheet's 1.7 approximation).

Reference values for common circular duct sizes (confirm exact Nederman product range before specifying). Change the velocity to update the table instantly. Equivalent to the two lower spreadsheet tables: airflow for a given diameter, or velocity for a given airflow.