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Do Air Purifiers Remove Viruses?

Many air purifiers claim to filter out and even kill bacteria and viruses. However, only those air purifiers equipped with HEPA (high-efficiency particulate air)-rated filters can capture the airborne virus-sized particles.

HEPA filters can trap only those airborne viruses that are circulating in the air at that time. Once trapped within the filter’s fibres, these viruses cannot remain infectious and multiply.

Although HEPA filters are effective in trapping viruses, these filters cannot kill the viruses. Thus, HEPA filters cannot provide complete protection against viruses. These can only trap a small per cent of viruses moving in your indoor environment.

You should not consider an air purifier as a substitute for the usual hygienic practices like washing your hands, sanitizing hard surfaces, etc.

HEPA filters 

HEPA (high-efficiency particulate air) filters are highly effective filters that can trap and remove up to 99.97% of particles of 0.3 microns and above. Most of the viruses vary from 0.02 microns to 0.4 microns in diameter.

Most of the viruses are well below the particle size that HEPA filters can capture. However, HEPA filters can still trap such tiny viruses when they contact the filter fibres while passing through them.

HEPA filters comprise a complex maze of tiny fibres carrying an electrostatic charge. This charge attracts the bypassing particles like a magnet instead of trapping particles like a net.

This is how the HEPA filter’s maze-like fibres capture tiny particles below 0.3 microns like H1N1 flu viruses. The nanoparticles move in a random pattern and stick to fibres. While the larger particles travel straight, make an impact, and get trapped by fibres.

A study by NASA in 2016 had suggested that HEPA filters are highly effective, with nearly 100% efficiency in capturing the very smallest airborne particles.

However, an air purifier with HEPA filters cannot protect from viruses. These air purifiers only serve as an additional protective measure, and that too if properly placed in the room.

When an infected person coughs or sneezes, viruses spread in the air and carried by the water vapour in the form of tiny droplets. These viruses remain infectious while they are suspended for several hours in the air. Eventually, these are inhaled by the individuals.

The reliable way for removing virus-sized particles from the indoor air is by circulating the complete volume of indoor air multiple times per hour through the air purifiers. This enhances the possibility of viruses entering the filters and getting trapped by the fibres.

A HEPA air purifier minimizes airborne transmission and supports overall health by blowing cleaner air in indoor and shared air-breathing spaces.

Photocatalytic Air Purifier

A photocatalytic air purifier generates electrostatic ions and employs oxidation effects for trapping and killing bacteria and viruses. However, it is not effective for killing all the viruses present in the entire air circulating in the home.

Ultraviolet Air Purifier

An ultraviolet air purifier serves as an excellent sterilizer by using the UV rays for sterilizing any enclosed spaces. But this air purifier requires viruses and bacteria to remain exposed to UV rays for several minutes for killing them.

If an air purifier uses UV rays to sterilise the filters that have captured the viruses and bacteria, it works effectively in killing them. However, if air passes through a UV light quickly, it may not deliver the desired result.

Catechin-based filters 

The air purifiers equipped with catechin-based filters also feature antiviral properties. These filters are prepared using plant extracts with antibacterial and antifungal properties.

Carbon filters

The air purifiers with carbon filters work great for trapping various air pollutants, volatile organic compounds (VOCs), odours, etc. However, it is not effective against trapping viruses and bacteria.

It uses activated carbon filters that trap the air pollutants when they pass through it.

Even though an air purifier with HEPA filters is technically capable of trapping any airborne viruses like H1N1 viruses that pass through it, it does not kill the trapped viruses. The trapped viruses may remain alive for several hours or days.

If you happen to replace your clogged filters with trapped but active viruses, you may still get infected by these viruses. Moreover, an air purifier captures viruses only from the sucked-in air.

An air purifier cannot prevent you from viruses found on a person’s skin, hard surfaces, floors, and other infected places. All the above- mentioned filters or sterilizers could only trap those airborne viruses or bacteria that passed through them.

Thus, you need additional ways like maintaining proper hygiene and boosting your immune system apart from installing air purifiers for breathing pure air.

Air purifiers don’t serve as the first line of defence for protection against viruses. There is no alternative to wearing masks, maintaining social distancing, and practising excellent hygiene at work and home.

An air purifier with HEPA filters can trap ultrafine airborne particles. This can be a useful addition to your defence strategy for preventing virus transmission.

As airborne transmission is only one way of virus-transmission, an air purifier can’t guarantee complete protection. It can remove pollutants from the indoor air but cannot avoid all modes of virus transmission.