Guidelines

Defined as the air volume required to be extracted or supplied into a room during a given period.
Several methods can be used to calculate the required airflow:

The fan selection must consider parameters such as:

Type of premises - industrial, commercial, domestic
Nature of the air and its characteristics - clean air, air & dust or grease, special fluid (gases)
Nature of the installation - supply and extract, wall fan, roof fan, ducted systems, position of the air entries, particular conditions
Requirements of air flow and pressure drop
Acceptable sound level in the room and externally
Type of mains supply - single phase, three phases, voltage, frequency
Other parameters may be considered for the selection such as dimensions, speed controllable motors, mounting accessories etc.

To obtain airflow in a ducted system it is necessary to overcome the resistance of the system:

- due to friction in the duct length
- due to the features of the system (bends, cross-section changes, filters, louvres etc.).

These losses must be calculated accurately to select the correct fan and to give the airflow required

In the catalogue, the sound level specified in the performance guide is a pressure level generally measured at 1,5 metres from the inlet for centrifugal fans, and at a distance equal to 3 times the impeller diameter (with a minimum of 1,5 m) for the axial flow fans.