Ventilation: a guide to reducing risk of COVID-19 transmission

The virus that causes COVID-19 can be spread from person to person through contact with droplets produced when someone sneezes or coughs, or through other small respiratory particles produced when people talk, sing or shout.

These small particles can remain in the air for some time and may build up if there is not enough ventilation.

This is the reason ventilation – the deliberate introduction of fresh air and removal of stale air from a space – is so important in preventing the transmission of COVID-19.

Open or well-ventilated spaces reduce the risk of transmission because infectious particles are more quickly diffused in the open air, than in spaces with less ventilation.

This is one of the reasons why COVID-19 transmission is more common indoors, where people may come into contact with infectious droplets and aerosolised particles more easily.

To help reduce the risk, NSW Health provides the following guidelines on ventilation for the general community:

• Use outdoor settings wherever possible. This is because outdoor settings have better natural airflow than indoor areas in most cases
• If it is necessary to use an indoor setting, use large-well ventilated spaces.
• Take steps to improve ventilation in indoor settings by opening windows and doors.

When opening windows is not possible, e.g. in larger buildings, NSW Health recommends:

• Regularly inspecting, maintaining and cleaning heating, ventilation and air-conditioning (HVAC) systems.
• Avoid using only recirculated air in HVAC systems by increasing the outside air intake.
• Avoid directing fans towards people's faces and limit oscillation and turbulence of fans.
• Consider disabling ventilation controls with automated settings that reduce air supply.
• If in place, ensure exhaust fans are in operation.

In situations where it isn't possible to modify ventilation, consideration could be given to:

• 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 people spend indoors together.

Businesses and organisations seeking individualised advice should consult relevant experts.