- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 27 Sep 2019
Stale air (sometimes called vitiated air) is air that has been affected by human, animal, mechanical or other activities, the effect of which requires that the air is replaced with fresh air to ensure optimal conditions. This might be the result of perspiration, smoking, cooking, use of appliances, musky carpets and fabrics, lack of ventilation and so on.
In their calculations for air extraction, services engineers may consider specific volumes of stale air in m2 to be extracted per hour. They typically work to achieve desirable minimum fresh-air requirements for people and these will vary according to the activities concerned. These ventilation rates or air-change rates determine how many times per hour the stale air in a space should be completely replaced by fresh air.
|Accommodation||Air-change rates per hour|
|Factories (large, open)||1-4|
|Classrooms and libraries||2-4|
|Offices (above ground)||2-6|
Air change rates may need adjustment according to specific conditions that might prevail eg whether smoking will take place or the presence of other fumes. Also, higher levels of relative humidity (ie above 70%) may require higher ventilation rates to reduce the water vapour content in the air.
 Related articles on Designing Buildings Wiki
- Air change rates.
- Air conditioning.
- Air handling unit.
- Air infiltration.
- Air infiltration testing.
- Approved Document F.
- Background ventilator.
- BREEAM Potential for natural ventilation.
- Computational fluid dynamics.
- Cross ventilation.
- Dew point.
- Displacement ventilation.
- Domestic ventilation systems performance.
- Fresh air.
- Heat recovery ventilation.
- Indoor air velocity.
- Locating ventilation inlets to reduce ingress of external pollutants into buildings: A new methodology IP 9 14.
- Mechanical ventilation.
- Natural ventilation.
- Passive building design.
- Preventing overheating.
- Retrofit, refurbishment and the growth of connected HVAC technology.
- Stack effect.
- Thermal comfort.
- Underfloor air distribution.
- Vertical riser.
- Whole building ventilation.
Featured articles and news
Chancellor announces latest Winter Support packages.
Tapping technology to boost infrastructure and create jobs.
4 ways to ensure certificates are valid.
White elephant construction projects.
How Paul Williams bent over backwards to overcome racial barriers.
Organisation revises actions around dealing with COVID-19.
CIOB, NFCC, RIBA, RICS call for changes ahead of Building Safety Bill.
Developments in the Future Homes Standard.
An American chimney feature with a colourful past.
Homes based on need, not ability to pay.
Historic England adds 216 entries to the 'at risk' register.
Will cycling and walking provisions be preserved?
Assembly point levels range from relative to ultimate.
Signs are pointing to a recovery for the construction industry.