How it is calculated
Rated airflow is measured with almost no resistance in the way. A filter and a long duct reduce the real flow, so an allowance is often added to the number.
m³/h = length × width × height × air changes
Where the numbers come from
- Length — unit in the field: m
- Width — unit in the field: m
- Height — unit in the field: m
- Air changes per hour
Example
A kitchen of 4×3×2,7 m at 12 air changes needs about 389 m³/h.
Questions
Where does the factor of 12 come from?
A common household figure for a kitchen, not the spec of one particular home.
Are recirculation and exhaust the same?
The formula is about the airflow you need. Recirculation does not exhaust the air, but the capacity on the label is read the same way.
A bathroom?
The air-change rate there is usually lower. Enter your own.