Instead, he thinks products that successfully marshal aerosol particles, the microscopic droplets of liquid that carry the virus, are worth spending money on, but he concedes it’s often difficult for consumers to work out which ones do what they claim. Jimenez said that a colleague often tells him that 50 per cent of air purifiers are not worth having. “I think that’s a very modest estimate,” he added.
There are two options, Jimenez said: Devices that remove the virus from the air or devices that leave it in the air but render it non-infectious by damaging the protein coating used to bind to human cells.
HEPA filters take the first approach by pushing the air from a room through minute fibres with distances of around a micron, in the process removing 99.7 per cent of contaminants, including COVID-19 particles, from the air, according to the CDC.
Prices vary from about £150 to as much as £1,000, but Linsey Marr, a professor of environmental engineering at Virginia Tech university, said a lot of the add-ons for more expensive versions are “unnecessary”. “Once the virus particles have stuck to the filter, you don’t then need to apply UV or an ioniser to them, they’re not coming back, unless you start waving the filter around,” said Marr.
The Belgian government has recently joined Taiwan in mandating the use of carbon dioxide monitors in certain public spaces to help in the fight against COVID-19. As people emit CO2 when they breathe out, such monitors are a helpful corollary for the likely spread of coronavirus particles in a poorly ventilated room, according to Jimenez.