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Can air purifiers help to prevent Covid-19?

​Studies have shown that some Covid-19 infections can be spread by exposure to small droplets and particles of the coronavirus that linger in the air for minutes, or even hours.

Can air purifiers help to prevent Covid-19?

Air purifiers are ostensibly useful as they offer some good protection against the transmission of airborne viruses and aerosols, while reducing potential allergen triggers in the environment.

​Studies have shown that some Covid-19 infections can be spread by exposure to small droplets and particles of the coronavirus that linger in the air for minutes, or even hours. 

As a result, retailers have reported a surge in sales of air purifiers since the onset of the pandemic.

These devices are ostensibly useful as they offer some good protection against the transmission of airborne viruses and aerosols, while reducing potential allergen triggers in the environment. 

Air purifiers usually comprise multiple filters and a fan. The fan sucks in surrounding air and pushes the air through the filters, and then circulates the purified air back to the room.

As the air moves through the filters, pollutants and particles are captured and the clean air is pushed back out into the living space.

There are many types of air purifiers in the commercial market.

Common ones here include the High-Efficiency Particulate Air (Hepa) purifiers, ultraviolet air purifiers, activated carbon air purifiers, and ionic air purifiers.

Some specialised air purifiers employ short-wave ultraviolet light (UV-C light) to inactivate airborne pathogens and microorganisms like mould, bacteria and viruses. They share the same ultimate goal as all air purifiers, that is, to reduce indoor air pollutants.


Most portable air purifiers with an efficient Hepa filtration system can certainly help to reduce the risk of airborne transmission of Covid-19.

A high-quality Hepa-based purifier can remove 99 per cent of contaminants from the air, including the respiratory droplets that spread the coronavirus.

These air purifiers capture the virus on the filter media. Once the viral particles are captured, they no longer grow and cannot be released.

Ioniser purifiers are another type of air purifier known to be effective against Covid-19.

They utilise a high voltage to generate and release charged negative ions into the air, which stick to the viruses, thereby killing them.

Once the viruses are destroyed and no longer pose further harm, they are then stuck to other charged surfaces like walls and tables which can be easily wiped down.

Others have found UV air purifiers to be the best air purifier for Covid-19 protection as data has shown that UV light can kill the coronavirus. Accordingly, UV light air purifiers seem to provide an effective way to kill viruses such as the coronavirus in the air.

All three types of purifiers are effective against Covid-19. 

The Hepa filter air purifiers hold an advantage over the other two purifiers insofar as they do not release any harmful or dangerous pollutants, such as ozone (from ionisers) or UV light (from UV light air purifiers). 


There are a few things a user should keep in mind to achieve the best results from an air purifier.

Firstly, ensure that there are no objects blocking the air intake and outlet passages so that the purifier can draw in more air. By doing so, the device can trap and remove more allergens and micro organisms before distributing fresh, clean air to the room.

Secondly, keep all windows and doors closed because air purifiers work best in enclosed spaces —  the confinement of the room maximises their potential to remove allergens and micro organisms faster and more efficiently.

Thirdly, it is recommended to leave an air purifier running 24/7 under its auto-mode function. Using this feature, its air quality sensor will continually monitor air quality by detecting the level of pollutants in the air.

When levels are high, the purifier automatically operates at a higher speed to clean the room faster.

If it detects low pollutant levels in the air, it will set the purifier to its lowest speed. During lower speed operations, the air purifier operates quietly while consuming less energy.

Finally, to sustain the purifier’s best performance, it is recommended that the user maintains the filters regularly.

For instance, most air purifiers have a washable pre-filter which can be washed and dried after every 10 to 15 days of use.

Paradoxically, air purifiers can also degrade air quality.

After prolonged use and without maintenance, dirt and bacteria that accumulate on the filters can be released back into the room. Proper operation requires equipment servicing and replacement of filters and other parts periodically.


To choose an air purifier of an appropriate size for one’s needs, consider the floor area of the room to purify.

In addition, one may wish to consider an air purifier with a higher air change per hour rate if any members in the family have allergies or asthma, and are looking for an air purifier to help manage their symptoms.

After choosing the type and size of the air purifier, one may also consider additional special features.

These include features such as energy star-rating to save money and conserve energy, auto-mode function that provides real-time air quality updates and adjusts air flow speed based on the levels of detected pollutants, as well as more advanced features that can even facilitate a Wi-Fi connection so users can control the purifier from their phones.

Ultimately, air purifiers are not silver bullets to combat Covid-19.

People must continue to employ ongoing mitigating measures such as wearing masks at all times, and practising good social distancing, in order to reduce the spread of the coronavirus through droplet transmission.



Ernest Chua is an associate professor at the National University of Singapore’s Department of Mechanical Engineering. His research focuses on developing novel solutions in biothermal therapies, renewable and clean energy technologies, such as cooling and dehumidification, building energy management and performance, as well as waste energy conversion systems. 

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