Mechanical Ventilation System
In commercial developments, mechanical ventilation is typically driven by air handling units (AHU) connected to ductwork within the building that supplies air to and extracts air from interior spaces. Typically AHU comprise an insulated box that forms the housing for; filter racks or chambers, a fan (or blower), and sometimes heating elements, cooling elements, sound attenuators and dampers. In some situations, such as in swimming pools, air handling units might include dehumidification.
Where mechanical ventilation includes heating, cooling and humidity control, this can be referred to as Heating Ventilation and Air Conditioning (HVAC).
Extracting internal air and replacing it with outside air can increase the need for heating and cooling. This can be reduced by re-circulating a proportion of internal air with the fresh outside air, or by heat recovery ventilation (HRV) that recovers heat from extract air to pre-heat incoming fresh air using counter-flow heat exchangers.