Crabb runs a mental “airborne audit” for most spaces he enters: how many people are here? What’s the ventilation like? Are we in a time of high transmission?


Some spaces he avoids or wears an N95 mask. Those he judges safer, he attends with his personal air purifier. “They are the bottom of the chain of controls – we don’t even know how effective they are, frankly.”

Crabb’s workplace has developed its own clean air strategy to monitor and filter office air (it helps to be the boss). At home, he has deployed three or four air purifiers. With the help of open windows, his goal is to completely turn over the air in his house at least six times an hour.

“I don’t want to get COVID. I certainly don’t want my family to get it,” he says. “Even though I almost certainly will, I want to get it as few times as possible. Clean air is at the heart of my own personal strategy.”

Professor Lidia Morawska, director of the International Laboratory for Air Quality and Health at Queensland University of Technology, is among the world’s foremost experts on air pollution and airborne transmission. She’s meeting a group of scientists on Friday night for dinner, she tells me. “Everyone is asking the question: ‘Will it be well ventilated? Or outside?’”

To deal with such situations, Morawska now keeps a list of well-ventilated restaurants – and ones with nice patios.

Air pollution and airborne transmission expert Professor Lidia Morawska.

Air pollution and airborne transmission expert Professor Lidia Morawska.Credit:QUT

She does not wear a mask everywhere she goes. “It depends on the situation,” she says. It’s about ventilation and time. If she’s spending a lot of time in a room, or close to someone, and the room’s poorly ventilated: mask on. A quick trip to the supermarket? Mask off.

In the car, Morawska usually has her air conditioner on recirculate to avoid pollution from other cars. But on a longer drive, carbon dioxide levels can build up in the cabin and make drivers sleepy. For long trips she makes sure there’s plenty of fresh air coming in.

Sick of catching so many colds from my young daughter, I installed a couple of air purifiers in my house late last year. Morawska’s verdict: they probably don’t do anything. Sure, they cut the virus in the air – but if you’re hugging your daughter, you’re still going to get sick.


Occupational hygienist and mask expert Kate Cole carries a small carbon dioxide monitor nearly everywhere she goes. Humans breathe oxygen in and carbon dioxide out; measure the levels and you have a crude proxy for how many people you’re sharing the air with. Cole uses the monitor to help her decided if she needs to don an N95.

“It’s not going to tell you you’re going to get COVID,” says Cole. “But it’s a crude measure to help understand when you’re in a place that would present a high risk of exposure.”

Ultimately, all these measures are up to the individual. Crabb admits his regime isn’t sustainable. “They are the stopgap,” he says, until – if – governments act on air quality.

We don’t leave salmonella testing up to individuals, and neither should we clean air. “This should not be our personal responsibility whatsoever,” says Morawska. “We need indoor air quality standards – and they should be legislated.”

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