September 6, 2021
We know how important clean water is – with COVID-19 we need to be just as fussy about the air we breathe, and ventilation is key. In this context, ventilation means provision of safe, clean indoor air, not to be confused with ventilation (assisted breathing) of patients in ICU. Schools and businesses have immediate needs for better ventilation, and urban design needs to incorporate improved airflow in a post-COVID world. SARS-CoV-2 spreads through the air. The risk of COVID-19 infection is higher in indoor spaces, and it’s even higher when those indoor spaces are poorly ventilated. Respiratory aerosols from breathing and speaking accumulate in indoor spaces, much like cigarette smoke but invisible. Risk of infection increases risk over time. Spending 10 minutes indoors in a poorly ventilated room is less of a risk than spending hours in there – so homes and workplaces are high risk. Many studies of cluster outbreaks of COVID-19 point to airborne transmission as the most likely explanation for infections. Poor ventilation (stagnant air) in public buildings, apartment blocks, workplace environments, schools, hospitals, and aged care homes contribute to viral spread. Good ventilation is one of the most effective ways to reduce the risk of COVID-19 infection, in concert with other mitigations, including density limits, the use of PPE and the use of air purifying devices.
High risk of SARS-COV-2 transmission can be identified with the three V’s and T (any of these is a red flag, and more than one indicates higher risk):
Venue: Multiple people indoors, where social distancing is often harder.
(poor) Indoor Air (Ventilation): Staying in one place with limited fresh air.
Vocalization: Talking, shouting or singing will increase aerosolization of the virus.
Time: The amount of time spent in the venue in relation to the risk. Less time is better.
- Test: Use a CO2 meter to check and to monitor ventilation in the space. This tells you how much of other people’s exhaled breath you are inhaling. If it is a public space, consider making the reading visible to the public. Don’t guess, test. C02 meters are cheap and easily accessible.
- Remediate: Act as required to improve ventilation to the target level of less than 800 ppm. (recommendations are below)
- Ameliorate: If immediate ventilation improvements are impractical, ameliorate conditions using air purifying devices. At a minimum, these should have a HEPA filter and the size of the unit should be matched to the space. Alternatively, relocate activities outside or to a better ventilated venue.
In a pandemic with a novel virus, it is important to be precautionary and to focus on minimising harm.
The full advice is available for download below.
Quotes from OzSAGE working group:
“Most infections occur in shared indoor spaces. The most fundamental measure to eliminate the virus from indoor air is ventilation: every public building must have control measures to provide adequate ventilation.”
Prof Lidia Morawska
“The highest priority is making sure that schools are safe, as children under 12 will be unvaccinated. Many children under 16 will also be unvaccinated. We can reduce the risk of transmission of COVID-19 by practical initiatives such as:
- Checking ventilation using a CO2 meter and opening windows where this is possible. Don’t guess, test. A serviceable CO2 meter can be bought for less than $200, with some much less. A Non Directional Infra Red (NDIR) Sensor type is best
- CO2 should be less than 800 ppm; outside air is 400 to 415 ppm.
- Children wearing masks where this is possible and all adults wearing N95 masks, all the time.
- Limiting the time in any location to no more than 45 minutes and allowing at least 15 minutes for the air to be ventilated.
- Holding classes outdoors where possible.
- Avoiding congregating in staffrooms. When staff need to remove masks to eat or drink, this should be done away from other people.”
Prof Geoff Hanmer
“Think of covid as spreading like deadly cigarette smoke – it builds up and is removed in the same way, but you can’t see it. Just as workplaces must be free of smoke, we must provide fresh air and sometimes filters and masks to protect workers and visitors. By ensuring we breathe fresh air, we can avoid most covid transmission. Where we can’t freshen up rooms, we need good masks, filters to clean the air, and less people. Something as simple as opening windows and not recycling air inside vehicles can make a tremendous difference”
Dr Andrew Miller
“One of the best ways to reduce people’s anxiety about COVID-19 is to make real changes that decrease the risk of infection. Safe indoor air is an extremely important and effective intervention, yet largely overlooked in Australia to date. CO2 monitoring, improved ventilation, improved filtration, and better masks for everyone aged 2 and older, will make a huge difference to indoor air quality and COVID-19 risk. Parents will feel a lot better about sending their kids to school once they know they will be breathing safer air.”
Dr Benjamin Veness