Work out hood airflow requirement instantly with clear inputs, formula shown and shareable results.
For an enclosing hood, airflow is simply face area times the required face velocity, typically 0.5 m/s for a fume cupboard and up to 1.0 m/s for open booths. The connecting duct is then sized on transport velocity, which must be high enough to keep dust and mist entrained, usually 10 to 20 m/s.
Hood airflow
Q = face area x face velocity
Duct size
Duct area = Q / duct velocity; diameter = sqrt(4A / pi)
Preliminary estimate only. Hood and duct design must follow a recognised industrial ventilation standard and be verified by measurement on commissioning.
Q = face area x face velocity. For an enclosing hood, airflow is simply face area times the required face velocity, typically 0.5 m/s for a fume cupboard and up to 1.0 m/s for open booths.
Face velocity only has to capture contaminant at the opening. Duct velocity must keep particles suspended along the whole run, otherwise dust settles and eventually blocks the duct.
This calculator takes 4 inputs: Hood width, Hood opening height, Required face velocity, Design duct velocity. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.