5. How to improve mechanical ventilation (including air conditioning)
Mechanical ventilation brings fresh air into a building from outside.
You should speak to the people who manage the day-to-day operations of your workplace’s mechanical ventilation systems to:
- understand how they operate
- make sure they’re supplying fresh air into an area and how much
- make sure they’re maintained in line with manufacturers’ instructions
Don’t lower mechanical ventilation rates if the number of people in an area reduces temporarily.
You should base ventilation rates on the maximum ‘normal’ occupancy of an area.
Maximising fresh air
Mechanical systems will provide adequate ventilation if they are set to maximise fresh air and minimise recirculation.
If your system draws in fresh air, it can continue to operate. You need to know how much fresh air it draws in and if this provides adequate ventilation.
You may need to increase the rate or supplement it with natural ventilation (for example, by opening doors, windows or air vents) where possible.
You could also consider extending the operating times of mechanical ventilation systems to before and after people use work areas.
It’s better not to recirculate air from one space to another.
Recirculation units for heating and cooling that do not draw in a supply of fresh air can remain in operation as long as there is a supply of outdoor air. This could mean leaving windows and doors open.
Recirculation units (including air conditioning) can mask poor ventilation as they only make an area feel more comfortable.
Find out more
Our examples of improving ventilation to reduce transmission provide further advice on practical steps you can take.
We review and update this page regularly to reflect any changes in guidance.
Page last reviewed: 30 September 2021
Next review due: 31 October 2021