Widely used to describe simply the cooling of an area (see “comfort cooling”). Its true technical meaning is to specifically control the following parameters:
The term is more appropriate to high tech applications such as calibration rooms, clean rooms etc.
AIR CHANGE RATE
The number of times air is introduced/extracted from a space. This air may be fresh air or purely recycled air, which is heated or cooled (for instance by the internal unit two piece cooling system. See ventilation, fresh air). This should not be used to determine fresh air requirements. Rather it is an indication of the approximate amount of recirculated air needed to adequately distribute heating or cooling.
Used to describe the composition and condition of air in a space. Air quality can be adversely affected by:
This describes the process of chilling an area using active refrigerant cooling to provide more comfortable conditions, often inaccurately referred to as “air conditioning”. This is typical of vehicle “air conditioning” and most office, factory or domestic installations. Typically these systems control over a temperature range of 3-4 °C which is adequate for most comfort cooling applications.
AMBIENT AIR SUPPLY
Air taken from outside to reduce internal air contamination and improve air quality. The source of this air should be as remote as possible from external pollution e.g. roads. The air will be at external conditions (e.g. temperature) and may require tempering (heating and cooling) to be acceptable. This air is not necessarily always cold and hence does not always provide any cooling effect. In many situations, there is a legal obligation to make provision for fresh air for occupants (see air quality, ventilation).
A very vague word used in a general sense. Sometimes it is used to describe conditions, which are either:
Sometimes it is used to describe all three at the same time! Use of the term should be avoided - rather use one or more of the above.
Indicates a change of air either by:
Usually ventilation utilises fresh external air (see ‘Fresh Air’) but it may also be totally recirculating.