N°2 – Type and position of air boxes training (VTC to A level)

The air handling unit can be made up of one single blower box.

• Single blower box without return air (100% fresh air).

Note:
If the AHU delivers fresh air, the same air flow is discharged outside the building. If this was not so, the building would swell like a balloon…. Exhaust air is either discharged by extraction like above, or by leaks due to the overpressure of the building (see below).

Extraction and overpressure of rooms can combine:

The air handling unit can be made up of one single blower box (contd.):

• Single blower return air box without fresh air (recycling box).

• Single blower box with fresh and return air.

The AHU below allows the distribution of fresh air and recirculating return air.

The air handling unit can be made up of two boxes, one blower and one return (in-line or stacked).