Work out local exhaust capture velocity instantly with clear inputs, formula shown and shareable results.
For a hood drawing on a source at distance X, the classic relation Q = V x (10 X² + A) reflects that air converges from a hemisphere in front of the opening. Adding a flange blocks air drawn from behind and reduces the required flow by about twenty-five percent for the same capture velocity, which is the cheapest improvement available.
Capture airflow
Q = coefficient x V x (10 X² + A)
Flange effect
Flanged hoods use a coefficient of 0.75
Preliminary estimate only. Local exhaust ventilation must be designed by a competent engineer to a recognised industrial ventilation standard and commissioned by measurement.
Q = coefficient x V x (10 X² + A). For a hood drawing on a source at distance X, the classic relation Q = V x (10 X² + A) reflects that air converges from a hemisphere in front of the opening.
The 10X² term means airflow rises with the square of distance. Doubling the standoff quadruples the exhaust needed, so bringing the hood closer is the single most effective change.
This calculator takes 4 inputs: Hood face area, Distance from hood to source, Required capture velocity, Hood type. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.