Can air purifiers help with COVID-19?

Avleen M.
Avleen M.Published on 5 Oct 2021

On their own, air purifiers are not a magic solution when it comes to stopping the spread of COVID-19. However, when used as part of a COVID-protection plan, using the right air purifier in your home or office can reduce the number of airborne particles that contain the virus - adding an extra measure of protection when it comes to staying healthy.

two staff in small office wearing masks and with air purifier

The two types of contaminants

According to a World Health Organisation brief, COVID is spread when small liquid particles are transferred from an infected person’s mouth or nose into the air, when they speak, cough, sneeze, sing, or breathe.

There are two types of particles that spread COVID-19. The first are larger respiratory droplets, which are 5 microns or larger in size. These droplets quickly fall to the ground or onto other surfaces - making sanitising surfaces of prime importance.

The second type of contaminants are smaller aerosol particles. These are airborne particles that travel on tiny droplets, ranging in size from 0.1 microns to 1 microns. For scale, the width of a human hair is around 70 microns. These airborne particles can linger in the air from anywhere for hours. After 15 minutes, these travel further than the recommended 1.5 metres of social distance and are easily inhaled.

Can an air purifier help with COVID-19?

HEPA filters

An air purifier with a true HEPA filter can trap 99.97% of airborne contaminants as miniscule as 0.3 microns. Since aerosolised coronavirus particles are 0.1-1 microns, this means air purifiers with HEPA filtration can trap 70% of these contaminants.

The HEPA filter on an air purifier will trap these particles in its fibres, and stop them from being released back into the room. However, a HEPA air purifier won’t kill COVID virus particles. They can survive on the filter for up to 72 hours after being trapped.

If you then touch the filter surface (for example if removing it or cleaning it), you can make contact with the living virus particles and become infected. The particles can also be disturbed and recirculated into the air. While it’s tempting to frequently check or clean the filter, it can be dangerous to do so.

UV Filters

Air purifiers with UV filters run air through an ultraviolet light to kill microbes like viruses, bacteria and mould spores. They are also known as sanitisers. Unlike HEPA filter air purifiers, UV filters don’t trap contaminants, but kill them before recirculating the sanitised air back into the room.

While this sounds like an ideal solution for destroying virus particles, there are some drawbacks. UV filters need to use a specific type of UV light called UV-C light to be effective. UV-C ligth can destroy the genetic material in virus particles, such as proteins. However, an air purifier must use 254nm light to destroy virus particles so they can’t reproduce.

However, research has shown that UVC-light at these wavelengths is dangerous and poses a health hazard to skin and eyes. There’s no guarantee that this UV-C light can’t leak out of air purifiers into a room.

Far-UVC light, on the other hand, is safer. You only need 222nm of far-UVC light to be effective against coronavirus particles, and have the same germicidal properties as regular UVC-light.

The downside is that there aren’t that many air purifiers with UV-C light filters available to buy. They also have a slower disinfection rate, leading to reduced effectiveness. They can remove 99.99% of coronaviruses in 25 minutes.

The best option is a far UV-C light that sterilises a filter after it’s trapped virus particles. This is better than a UV light that sterilises air that happens to pass through the filter - as the air may not be exposed to the UV light for long enough to be effective. It also means if you accidentally touch the filter, there's less chance of you touching virus particles.

What air purifiers can’t do to help

Air purifiers won’t be able to trap or kill virus particles that are contained in droplets on hard surfaces, or droplets or smaller virus particles already on a person’s body.

They’re also not a substitute for adequate ventilation and filtration, which reduce the risk of getting COVID-19 while inside a room by diluting airborne virus particles and cutting down the amount of time they spend in a room.

How do you ventilate a room naturally?

This involves adding clean air to a room, while removing stale air. It’s recommended that a room gets 4-6 units of air changes per hour (the standard in hospitals), and that the average household gets 0.35 air changes per hour.

You can increase the rate of air change in a room by doing the following according to the World Health Organisation: running heating and air conditioning (HVAC) systems, or opening windows and doors, and creating cross-ventilation by opening windows and doors on both sides of the room, if possible.

Avoid directional fans that don’t have filtration systems. This can blow infected air directly from person to person.

How do you filter air in a room?

As well as providing ventilation, HVAC systems in air conditioners filter the air in a room. Remember to upgrade or service the filters in your air conditioner’s HVAC systems. Using the AC with an effective HVAC system along with a HEPA air purifier can have positive results for improving air filtration in a room.

Some air conditioners have built-in air purifiers with HEPA filters, which can be effective as an all-round purification system. However, these are usually found on high-end air purifiers and can be quite expensive.

Putting it into a practical context

An air purifier may be helpful for your home, office or classroom in these situations:

  • You have a household member that has COVID-19 or needs to quarantine. Placing an air purifier in their room while they’re isolating can help clean the air in that room and help protect other household members.
  • A household member is at high-risk of getting COVID, or is vulnerable to developing complications from it (for example, if they have a health condition or are an older person).
  • You have a small office space that doesn’t have reliable air conditioning, and it’s not practical to keep windows open.

Air purifiers won’t be effective for:

  • Extra-large spaces (like large, open-plan offices) if the air purifier is not the correct size for the room. Large air purifiers can usually work for rooms of up to 1500 square metres. Any larger, and you may be better off sourcing a commercial air scrubber with a HEPA filter. These are designed for extra-large spaces.

The bottom line

While air purifiers shouldn’t be relied on as a single safeguard against COVID-19, they can go some way in trapping or even killing virus particles in the air.

To make the best use out of them, make sure to prioritise the following first: hand hygiene, sanitising hard surfaces, social distancing, wearing masks and avoiding crowded places. No air purifier can completely eliminate the risk of contracting COVID, but they can provide a little extra peace of mind when you're out and about after COVID restrictions ease in your state.