Mark Vender
OzSAGE, a multi-disciplinary network of Australian experts from a broad range of sectors, has issued advice on safe indoor air and ventilation to reduce the spread of COVID-19.
With the airborne spread of SARS-CoV-2 now widely accepted, OzSAGE has highlighted that the most fundamental measure to eliminate the virus from indoor air is ventilation. Every public building must have control measures to provide adequate ventilation.
“Think of COVID as spreading like deadly cigarette smoke,” says Professor Geoff Hanmer from the OzSAGE working group. “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.”
The guidance is written in non-technical language and is appropriate for a general audience. But it also breaks the information up for different types of indoor settings. These include naturally ventilated buildings, mechanically ventilated buildings, buildings with split systems, and vehicles. There is information about CO2 monitoring, pressure differentials, and short- and long-term strategies.
“One of the best ways to reduce people’s anxiety about COVID-19 is to make real changes that decrease the risk of infection,” says Dr Andrew Miller, also from the OzSAGE working group.
“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 two 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.”
A clear focus of the advice is on schools.
“The highest priority is making sure that schools are safe, as children under 12 will be unvaccinated,” says QUT’s Professor Lidia Morawska, part of the OzSAGE executive. “Many children under 16 will also be unvaccinated. We can reduce the risk of transmission of COVID-19 by practical initiatives.”
Prof. Morawska recommends checking ventilation using a CO2 meter and opening windows where possible.
“Don’t guess, test,” she says. “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 800ppm; outside air is 400–415ppm.”
Prof. Morawska also says children should wear masks where possible, and all adults should wear N95 masks, all the time (outside the home).
On top of this, the time in any location should be limited to no more than 45 minutes, allowing at least 15 minutes for the air to be ventilated. Where possible, classes should be held outdoors.
And staff should avoid congregating in staffrooms.
“When staff need to remove masks to eat or drink, this should be done away from other people,” says Prof. Morawska.
To read the full guidance document, click here.
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