Publication - Advice and guidance

Coronavirus (COVID-19): ventilation guidance

Getting fresh air into indoor spaces to help stop the spread of coronavirus.

Coronavirus (COVID-19): ventilation guidance


The provision of fresh air into indoor environments is essential to preventing the spread of COVID-19. By taking measures to increase the volume of outside air entering a building, such as opening windows, doors or vents, you can help minimise the risk of spreading COVID-19 to colleagues, friends, family members and customers. 

As we progress through winter, and people are spending more time indoors, effective ventilation becomes even more important and as such is a critically important measure to reduce the risk of transmission within enclosed premises, both in the workplace and at home.

That is why we have set up a £25 million business support fund, to support small and medium sized enterprises to make reasonable adjustments to premises to enhance ventilation. This will include the purchase of NDIR ( non-dispersive infrared detection) CO2 monitors to assist businesses in assessing their air quality and ventilation system. More information on eligible businesses and how to apply can be found at: Business Ventilation Fund on the Find Business Support website.

There are some really simple things businesses and individuals can do to improve ventilation such as using properly maintained mechanical systems, or opening windows, doors or vents a small amount regularly to improve the flow of fresh air in indoor settings.

This guidance is designed to support the mixing of individuals safely in indoor settings. It has two parts – one providing guidance for domestic, or home settings, and the other for non-domestic, or commercial properties.

Transmission risk

Coronavirus is mainly transmitted between people directly through droplet and aerosols and indirectly through contact with contaminated surfaces.

Droplet transmission occurs when an infected person coughs or sneezes and their respiratory droplets enter the mouth, nose, eyes or airways of another person.

Aerosol transmission is transmission via fine mists (aerosols) and droplets from breath containing the virus that are suspended in air. There is increasing evidence of the potential risk of aerosol transmission, particularly in poorly ventilated and/or crowded environments.

As a result, ventilation is an important factor in reducing the risk of aerosol transmission indoors, where individuals may be in close contact, potentially for longer periods of time.

As ventilation requirements vary depending on the situation and setting, the advice cannot easily be distilled into a simple one-size fits all solution. For workplaces or public spaces, it is therefore vitally important that a specific risk assessment is carried out which considers all spaces in each indoor premises.

Ventilation is not a substitute for other non-clinical interventions, such as environmental cleaning, face coverings or maintaining good hand and respiratory hygiene. It should be considered as part of a range of mitigation measures.


  • COVID-19 is spread through the air in droplets and aerosols (finer particles/ drops)
  • good ventilation helps reduce exposure by dispersing droplets and aerosols
  • meet outside where possible – the risk of infection is reduced as the air dilutes the particles and moves them away from others
  • let fresh air indoors – letting fresh air indoors regularly throughout the day will dilute any infected particles and reduce the infection risk
  • in many home and business premises this will be done through opening vents, windows or doors
  • good ventilation will not stop the potential spread of COVID-19 on its own. It must be in addition to other protective measures such as enhanced hygiene regimes and face coverings

A poster providing good ventilation advice that can be printed out and displayed is available.



First published: 18 Dec 2020 Last updated: 31 Jan 2022 -