3. Assessment of fresh air (ventilation) in the workplace

There are a number of factors to consider when deciding on the ventilation needed in your work areas.

Consider the following questions to help you build up a picture of the risk and decide if you need to take action to reduce it.

How do you provide fresh air (ventilation) to your workplace?

Adequate ventilation reduces how much virus is in the air and therefore reduces the risk from aerosol transmission for workers in that area.

You should maximise the fresh air in an area and this can be done by:

  • natural ventilation which relies on passive air flow through windows, doors and vents that can be fully or partially opened
  • mechanical ventilation using fans and ducts to bring in fresh air from outside, or
  • a combination of natural and mechanical ventilation, eg where mechanical ventilation relies on natural ventilation to maximise fresh air

Your workplace may have different means of providing ventilation for different areas. It may be helpful when doing your assessment to make a list of areas in your workplace and how they are ventilated. Floor or design plans may help with this.

Alternatively, you could walk around the building and make a note of each area and how it is ventilated.

Remember to include changing rooms and areas used for breaks, such as canteens. If you are not able to easily tell how an area is ventilated, it may be because it is poorly ventilated.

How many people use or occupy the area?

The more people who use or occupy an area the greater the risk that an infected person is there, increasing possible exposure to aerosol transmission. Reducing the number of people who use or occupy an area reduces this risk.

This risk increases if an area is poorly ventilated and occupied by more than one person.

Consider how many people use or occupy an area at any one time. Is there a set number of people each day or do numbers fluctuate?

How much time do people spend in the area?

The longer people use or occupy an area, the greater the risk. Consider how many people use or occupy an area for a sustained period (for example a full shift), and how many come and go throughout the day. Can you reduce this in any way? 

How large is the area?

The larger the area, the lower the risk. This is because larger areas:

  • have more air to help dilute the virus
  • tend to be designed with higher ventilation rates
  • mean it takes longer for aerosols to build up

What tasks or activities take place in the area?

Activities that make you breathe deeper, for example physical exertion or shouting, will increase generation of aerosols and increase the risk of transmission.

These activities increase transmission risk even in areas with adequate ventilation. If possible, avoid or redesign these activities to reduce the risk, for example moving activities outside or working alone where possible. 

Are there any features in the workplace that affect ventilation? 

You may have large machinery, equipment or other features that would prevent air circulating. This could create stagnant parts of the area so consider how to improve the flow of air in that area.

Do you use desk or ceiling fans?

Desk or ceiling fans should not be used in poorly ventilated areas.

Does your workplace use local exhaust ventilation?

Your business may use local exhaust ventilation (LEV) to control risks from other workplace hazards such as dust or welding fumes. If these discharge the air outside, they will increase ventilation in the area.

Is there a complex ventilation system?

Workplaces that may have complex ventilation systems include:

  • some old buildings
  • buildings with multiple floors and rooms, with different ventilation systems
  • systems designed for product manufacturing reasons, which may include additional recirculation

If your workplace has a complex ventilation system, there is guidance from the Chartered Institution of Building Services Engineers (CIBSE), or you may need to get a ventilation engineer to provide expert advice on what system you need to reduce any potential transmission risks.

How will you tell your employees about the outcome of your assessment?

You should tell your workers about the outcome of the risk assessment. This will help them understand how they can play their part to reduce the risk of spreading coronavirus.

This page is reviewed regularly and updated to reflect any changes in the guidance.

Page last reviewed: 30 April 2021

Next review due: 31 May 2021

Updated 2021-03-31