Metrology – the science of measurement – has a vital role to play in the modern world. Reliable measurement is critical to standardise and compare products and to compete in a demanding global market. Climate control requirements in metrology rooms are no less demanding.

The equipment used in metrology is subject to error owing to thermal expansion and contraction. This fact generally necessitates careful consideration of temperature control during installation, to prevent the exorbitant effort of patching it up. Generally, set points of between 20 °C and 25 °C are chosen, with allowable temperature variations of between 1 °C and 5 °C, depending on the type of work being done. In addition, humidity should be kept between 40% and 60% RH and air pressure at 10 Pa (or, for some applications, atmospheric pressure).

Metrology rooms are normally managed within a two-zone environmental control system. The first zone comprises the building in general and is designed to provide air-conditioning that is comfortable enough to work in. The second is the laboratory, which requires closer control but should only have to deal with the conditions already provided within the building. A dust filter system that allows for a slight positive pressure is preferred to minimize the influx of outside air and dust.

A large number of variables have to be taken into account in designing the climate control system of the room. These include the heat load produced by the number of occupants, the expense (specialised metrology room equipment can be costly), and the comfort of occupants. Poorly located or sized fans can cause draughts which can disrupt work, result in unwanted temperature gradients in the room and make the environment unpleasant.