2. Assessing the risk of poor ventilation
As part of your risk assessment to protect your workers and others from coronavirus (COVID-19), you should identify poorly ventilated work areas.
- Look for areas where there is no natural ventilation (open windows, doors, or vents) or mechanical ventilation (fans or ducts bringing air in from outside)
- If a mechanical ventilation system only recirculates air and has no outdoor air supply, the area is likely to be poorly ventilated
- Identify areas that feel stuffy or smell bad
- Consider using a CO2 monitor to identify poor ventilation
It may help to list areas in your workplace or use floor plans to record how they are ventilated. Remember to include changing rooms and areas used for breaks, such as canteens.
Numbers of people using or occupying an area
The more people who use or occupy an area, the greater the risk of aerosol transmission. The risk increases if an area is poorly ventilated and occupied by more than one person.
Consider how many people use or occupy a space at any one time. Is there a set number of people each day?
Larger work areas
The larger the area, the lower the risk. This is because larger spaces:
- have more air to help dilute the virus
- tend to be designed with ventilation rates in mind
- take longer for aerosols to build up in them
Activities that make people breathe deeper
Activities that make you breathe deeper, such as physical exertion or shouting, will increase the generation of aerosol and therefore increase the risk of transmission, even where there’s adequate ventilation.
Reduce the risk where you can, for example by moving some activities outside.
Features of the workplace that may affect ventilation
Large machinery, equipment or other features (such as pillars) could prevent air circulating. Consider how to improve airflow in the area.
Desk or ceiling fans
You should not use desk or ceiling fans in poorly ventilated areas.
Local exhaust ventilation
You may use local exhaust ventilation (LEV) to control risks from other workplace hazards such as dust or welding fumes. If an LEV system discharges the air outside, it will improve ventilation in the area.
Complex ventilation systems
If your workplace has a complex ventilation system, due to having multiple floors etc, there is guidance from the Chartered Institution of Building Services Engineers (CIBSE).
You may need a ventilation engineer to provide expert advice on the best system for your workplace.
Talk with your workers about your risk assessment
Talking with your workers about the outcome of the risk assessment will help them understand how they can play their part in reducing the spread of COVID-19.
Find out more
The British Occupational Hygiene Society has worked in collaboration with the Health and Safety Executive to develop a freely available tool for assessing general ventilation and COVID-19 transmission.
The tool supports employers, building users and building owners by using a simple scoring system to indicate the effect their ventilation arrangements are likely to have on reducing COVID-19 transmission. It also provides recommendations for taking action, where appropriate.
We review and update this page regularly to reflect changes in guidance.
Page last reviewed: 19 January 2022
Next review due: 30 January 2022