Work out smoke control airflow instantly with clear inputs, formula shown and shareable results.
Smoke control fans move hot gas, which occupies far more volume than the same mass of cool air. The cold air flow needed to hold a design velocity through the opening is area times velocity, and multiplying by the ratio of absolute temperatures gives the volumetric rate the fan must actually handle: at 300 °C that is nearly double.
Cold flow
Q cold = opening area x design velocity
Hot flow
Q hot = Q cold x (T smoke + 273) / (T ambient + 273)
Preliminary estimate only. Smoke control design must be carried out by a qualified fire engineer using recognised plume and layer models.
Q cold = opening area x design velocity. Smoke control fans move hot gas, which occupies far more volume than the same mass of cool air.
It handles the hot gas directly. Smoke extract fans are certified for continuous operation at elevated temperature, typically 300 °C for two hours or 400 °C for one hour.
This calculator takes 4 inputs: Opening area to be protected, Design air velocity through the opening, Smoke layer temperature, Ambient temperature. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.