Technical calculation · General ventilation
Ventilation calculation.
Calculate the required ventilation airflow, an example fan arrangement and the fresh air louvre area from the room volume and air changes per hour.
3D view
Air sweeps the space from end to end
Fresh air enters through the louvres, crosses the full length of the space and is exhausted by the fans. The building dimensions, number of fans and flow velocity come from your calculation.
Preparing the 3D view…
The illustration explains the preliminary calculation; it is not to scale. The view changes as you change the values.
Calculation method
How is ventilation airflow calculated?
In general ventilation, the airflow is found from how many times per hour the air in the space has to be replaced. In spaces with a high heat load, the airflow needed to remove the heat is calculated as well; the larger of the two values governs.
Worked example
A 40 × 20 × 8 m welding shop:
Volume: 40 × 20 × 8 = 6,400 m³
Airflow: 6,400 × 12 = 76,800 m³/h
Application: for example 6 fans × 12,800 m³/h and ≈ 10.7 m² of net louvre area for fresh air
| Type of space | 1/h |
|---|---|
| Warehouse, storage | 4 |
| General production area | 6 |
| Machining, assembly workshop | 8 |
| Welding and metalworking shop | 12 |
| Textile, heat-loaded production | 15 |
| Paint, solvent, chemical areas | 20 |
| Foundry, hot process | 25 |
These are approximate values for general ventilation; they do not replace extraction at source.
Points to watch
Common mistakes in ventilation
- Do not forget the fresh air inlet. As much air must enter as is extracted; if the louvres are too small the fans cannot deliver their airflow and doors become hard to open.
- Extraction at source is required. In work such as welding and grinding, general ventilation alone does not remove fume and dust; extraction at source (a local filter) is needed.
- Set up the airflow along the length of the space. Place fans and louvres opposite each other so that the air sweeps the space from end to end.
- The values in the table are typical. Where a regulation or process requirement applies, that value governs.
Leave the calculation to our engineers.
Send us your airflow, dust type and plant layout; we will size the fan, filter and duct line together and prepare your quotation.