About well-ventilated spaces
This guidance aims to support the community, businesses and organisations to understand why outdoor and well-ventilated indoor spaces reduce the risk of transmission of COVID-19, and to take action to stay COVID-safe.
For indoor environments, ensuring that heating, ventilation and air conditioning (HVAC) systems are well-maintained and operating properly may help to manage the risk of virus transmission.
For individualised advice, businesses and organisations should consider consulting relevant experts such as building owners or facility managers, ventilation engineers and industrial or occupational hygienists.
Some settings, such as healthcare, have specific recommendations which should be followed.
What is ventilation?
Ventilation is the deliberate introduction of fresh air and removal of stale air from a space.
Why is ventilation important?
The virus that causes COVID-19 can be spread from person to person through contact with droplets, which are produced when a person sneezes or coughs, or through other small respiratory particles that are produced when people talk, sing or shout.
These small particles can remain in the air for some time. Aerosolised particles may build up if there is not enough ventilation, for example, if a group of people sing or speak loudly in an indoor space without the windows or doors open.
Open or well-ventilated spaces reduce the risk of transmission of COVID-19 because infectious particles are more quickly diffused in the open air than in spaces with less ventilation.
Transmission of COVID-19 is more common indoors, where there may be less space to physically distance, and where people may come into contact with droplets and aerosolised particles more easily.
To help reduce the risk, it is important to take steps to improve ventilation in indoor settings so that any infectious particles that may be present in the air are more quickly removed.
What can you do?
Consider your premises or event and the types of activities that will be carried out. The steps you can take will depend on your specific circumstances. Some strategies may be more applicable to the general community and small businesses and organisations (such as going outside and opening doors and windows) than larger businesses and organisations. Businesses and organisations seeking individualised advice should consult relevant experts.
Use outdoor settings wherever possible
- in most cases, outdoor settings have better natural airflow than indoor areas.
If it is necessary to use an indoor setting, use large, well-ventilated indoor spaces
- avoid crowded or noisy indoor spaces
- crowds mean there are more people generating droplets and aerosolised particles. Noisy spaces encourage people to shout or talk loudly, increasing the generation of aerosolised particles, and therefore the risk of transmission of COVID-19.
Take steps to improve ventilation in indoor settings
Indoor ventilation can be most easily improved by opening doors and windows. Other ways to safely improve ventilation include to:
- avoid directing fans towards people’s faces, such as by aiming them continuously towards the ceiling or floor. Limit oscillation and turbulence of fans
- regularly inspect, maintain and clean heating, ventilation and air conditioning (HVAC) systems
- avoid using only recirculated air in HVAC systems, and increase the outside air intake
- consider disabling ventilation controls with automated settings that reduce air supply based on temperature or occupancy
- ensure exhaust fans are operational if in place.
If you can’t modify the ventilation or choose an outdoor location, you could consider:
- reducing the number of people in an indoor space at any one time
- avoiding peak activity times and the places where people gather together indoors
- reducing the length of time that people spend indoors together.
You may also reduce your risk by wearing a well-fitting face mask whenever you are indoors.
Last updated: 8 December 2020