The spread of certain respiratory diseases such as COVID-19 in indoor environments may be limited through improved ventilation. This is noted by the Australian Health Principal Protection Committee (AHPPC). Improved ventilation is a potential additional control measure within a hierarchy of controls. However, ventilation controls cannot replace other infection prevention and control mechanisms. The AHPPC states that factors that help to manage the risk of transmission of COVID-19 include:
- COVIDSafe plans
- physical distancing
- respiratory hygiene
- use of masks
- testing
- contact tracing
- isolating
- vaccination.
COVID-19 can be transmitted via:
- fine respiratory droplets and aerosol particles
- direct physical contact
- fomite / indirect contact transmission routes.
Aerosol transmission of COVID-19 can occur particularly in indoor, crowded and inadequately ventilated spaces, where infected persons may spend time with others. The World Health Organization (WHO) advises that the risk of COVID-19 spreading indoors may be reduced through well-designed, maintained and operational ventilation systems. Proper use of natural ventilation may provide the same benefits.
Ventilation controls may be relevant in high-risk indoor environments such as:
- schools
- aged care residential facilities
- dormitories
- correctional facilities
- offices and other workplaces.
However, ventilation controls must be managed appropriately. Different indoor environments pose different risks of viral transmission. It may not be appropriate transpose controls designed for one setting (for example quarantine), to another (for example, schools).
Where possible, air flow should be optimised to reduce viral load within a room to minimise the risk of exposure to airborne infectious material. Increasing natural ventilation through opening windows and doors may assist. However, it is acknowledged this may not be appropriate in some settings, and depends on several factors. Additional measures to consider, include the use of exhaust fans and air cleaning, or purification devices. However, AHPPC advises that appropriately experienced professionals should be consulted when considering changes to ventilation systems in buildings. These assessments should be made in addition to applying a range of infection prevention and control measures using the hierarchy of controls.
The appropriateness of a particular strategy will depend upon several factors, such as:
- building design
- occupancy level
- building operation
- environmental, seasonal and climate factors.
For example, while increasing the introduction of outdoor air may improve ventilation, this may not be appropriate in hot, cold or humid weather, or during periods of low outdoor air quality. Safe Work Australia’s website provides further guidance for businesses on managing the risk of transmission of COVID-19 in indoor workplaces. Practical tips to improve ventilation are also included.
Safe Work Australia has published a National guide for safe workplaces – COVID-19. The guide includes information on ventilation and heating, ventilation and air-conditioning (HVAC), and more detailed stand-alone guidance on ventilation and HVAC. This is included in a range of general and industry-specific advice, guidance and resources on Safe Work Australia’s website.
The information helps create and maintain a safe workplace during the COVID-19 pandemic. The AHPPC notes that Safe Work Australia continually reviews and updates their guidance to ensure it remains consistent with the current health advice. The AHPPC will engage with Safe Work Australia to inform future reviews of its guidance on ventilation.