We saw a spike in online traffic for air purifiers at the start of the pandemic as worried people were, understandably, looking for products to help prevent them getting Covid-19. 

Recent studies have indicated that air purifiers can reduce traces of airborne Covid-19 on hospital wards. But you shouldn’t solely rely on an air purifier to filter out the virus in your home. Read on to find out why that’s the case, how air purifiers can potentially help improve your air quality in other ways, and free ways you can breathe cleaner air at home.

---

Just want to see which air purifiers that impressed in our tests? See our list of Best Buy air purifiers.

You can also read the latest coronavirus news and advice from Which?

---

Air purifiers for coronavirus: do they exist?

At the start of the pandemic, some air purifier manufacturers implied, or outright claimed, that their machines would protect you from coronavirus.

Examples of manufacturers making direct claims about this include AllerAir (below, spotted on 25 March 2020)

And Airpura (spotted on 24 March 2020):

By 25 March 2020, the Airpura website had been adjusted to say ‘how an air purifier can kill airborne viruses’ rather than ‘how an air purifier can kill airborne viruses, such as coronavirus’.

These manufacturers only ship to Canada and the US, so their products aren’t available in the UK. And you could argue that, even if these products don’t work as well as claimed, there’s no harm in buying one. But there is a risk that such advertising gives false hope and could act as a distraction from official government advice.

Blueair air purifiers

In March 2020, air purifier manufacturer Blueair’s website stated:

‘Blueair air purifiers have not been tested for the removal of coronavirus yet, as it’s a new strain that was discovered in 2019.

‘However, here is what we do know: Blueair air purifiers have been third-party tested for the removal of the most common viruses and bacteria with a clearance rate of more than 99.99%. The tests included H1N1 influenza, staphylococcus aureus, E coli and aspergillus.

‘Blueair’s HEPASilent™ technology captures at least 99.97% of airborne particles down to 0.1 microns in size. This includes any viruses with a particle size of at least 0.1 micron. Corona viruses measure about 0.12 micron.’ 

Blueair air purifiers are often highly rated by Which?, but we are in no way saying that these products (or any commercial air purifiers) protect you from coronavirus.

We reached out to Blueair for comment in March 2020. Blueair told us that:

‘We have made it absolutely clear on our website that an air purifier will not protect you from coronavirus. We have also stated very clearly that Blueair has not tested against the new coronavirus. We have posted the information you refer to on our website in response to the many questions (including questions about particle sizes) that have been flooding in from all over the world – from consumers, hospitals and media – asking specifically about air purifiers and coronavirus.’

In April 2021, Blueair updated its website to say that it had now tested the ability of its HealthProtect 7400 series to remove live coronavirus particles from the air and that its results showed 99.99% of the live SARS-CoV-2 virus in its test were removed from the air. It also said these models were ‘not proven to kill SARS-CoV-2 or reduce or prevent Covid-19 transmission’.

Research on using air filter machines on Covid-19 wards

In November 2021, a research team at Addenbrooke’s Hospital and the University of Cambridge reported that they were able to use HEPA filter/UV steriliser air purifiers to remove most airborne traces of SARS-CoV-2 on surge wards at the hospital.

The air purifiers also successfully filtered out other bacterial, fungal and viral bioaerosols (airborne particles containing living organisms).

Intensive care consultant at Addenbrooke’s Hospital Dr Vilas Navapurkar, who led the study, told us: ‘We can remove SARS-CoV-2 and other infecting potential organisms from the air. We can measure how much is there in that proportion of air that’s breathable into the lungs that triggers injury. It’s the science of measuring the air that’s key here.’

This is an exciting development, which could allow hospitals to better manage airborne transmission of Covid-19 between patients and staff on the surge wards, with relatively inexpensive air purification machines, especially during peaks. However Dr Navapurkar stresses that further testing needs to be carried out, as there are many variables that could impact the effectiveness of an air purifier on a hospital ward.

‘Every room is different and every human is different. I don’t know whether one person has had an operation, has had steroids, is on immunosuppressants, if they’re a smoker or not. Their vulnerability is different.

‘The size, activity and disease burden of each room will also be different. For example, we can have a cardiac arrest in one bay but not in the other and that would throw up a plume of pathogens.’

Report on portable HEPA air cleaners and exposure to coronavirus

A July 2021 report from the Centre for Disease Control (CDC) in the US also suggested that portable HEPA air cleaners could reduce exposure to SARS-CoV-2 aerosols indoors.

It focuses on conference rooms, not household environments, and there’s a lot more real-world evidence needed – so the results don’t change our advice about air purifiers and Covid.

The CDC study simulated a meeting between an infected person exhaling aerosols, and three uninfected people, in a conference room for an hour.

A significant reduction in exposure to aerosol particles was observed with the HEPA air cleaners in place (and exposure was even lower when everyone in the room was wearing masks). But there are a few caveats.

For example, the study doesn’t measure the impact of having good ventilation in a room, which can affect air flow patterns, so we can’t compare which is better. The CDC does say that HEPA purifiers would need to be used as a supplement to good ventilation indoors.

The robots used to simulate meeting participants were also static, and there were only four of them – so the situation doesn’t account for people moving around a room, nor does it tell us about more crowded spaces like shops.

Also, the test concluded that the air purifiers are likely to be most effective when placed close to an infected person – but in real life it won’t always be clear who this is.

The CDC does acknowledge these and other limitations in its publication. It suggests that the use of portable HEPA air purifiers could supplement current building ventilation systems, in addition to other measures in public indoor spaces such as wearing face masks.

Air purifiers and particle filtration

Coronavirus particles do fall within the particle-size range that HEPA filters, found in some air purifiers, capture, which is 0.01 micron and larger. 

An air purifier could capture coronavirus, if the purifier had a particular type of HEPA filter with an efficiency of 99.95% and an ultra violet lamp to then kill coronavirus.

Crucially, though, in the real world, a lot depends on factors such as:

• the type of HEPA filter you have
• the size of your room
• the number of air changes in that room
• the state of the filter
• whether your air purifier is older and so has a fading UV lamp. 

How to stay safe during the pandemic

There is increasing evidence to show that Covid-19 can linger in enclosed spaces and that ventilation is key. 

Current government advice states that ‘while larger droplets fall quickly to the ground, smaller droplets and aerosols containing the virus that causes Covid-19 can remain suspended in the air for some time indoors, especially if there is no ventilation. Ventilation is the process of replacing this shared air with fresh air from outside. The more ventilated an area is, the more fresh air there is to breathe and the less likely a person is to inhale infectious particles’.

The government recommends:

• Let plenty of fresh air into your home by uncovering vents and opening doors and windows (if you are concerned about security, noise or the costs of heating, opening windows for a short period of time while you wrap up warm is still worthwhile).
• Leave extractor fans in your bathroom or kitchen running for longer than usual.
• Leave windows fully open for a short period after someone working in your home such as a cleaner or tradesperson has left.

It also states that if someone in your home is self-isolating, you should open a window in their room and keep the door closed to reduce the spread of contaminated air to other parts of the household.

It’s also important to remember that Covid-19 can also be transmitted through contact with respiratory droplets, when you’re in close proximity to someone, and surfaces.

To stay safe, follow the latest NHS guidance, including around household visits. Remember that you won’t need to worry about contracting Covid-19 from your air at home if you don’t admit someone into your home who may be infected. 

You should also:

• Wash your hands frequently and for at least 20 seconds.
• Cover your face in indoor settings where required, unless you’re exempt.
• Catch coughs and sneezes in a tissue.
• Avoid touching your eyes, nose or mouth if your hands are not clean.
• Obey the law regarding staying home and practising social distancing when it’s necessary to go out.

How an air purifier can help you improve your indoor air quality

When it comes to trying to stay healthy generally, regardless of Covid-19, breathing cleaner air can only ever be a good thing.

An air purifier shouldn’t be your first line of defence, though: if you can increase the flow of fresh air into your home by opening windows,  do that instead.

If that’s not a viable option – say, you live on a very polluted street or you suffer from hay fever – then an air purifier can help by trapping common allergens and delivering cleaner air. If you suffer from allergies, a good air purifier can help you by trapping pollutants such as dust and pollen particles.

Some air purifiers come with carbon filters, designed to also capture gases.

We know many people are interested in using air purifiers to tackle traffic pollution. Yet it’s currently impossible to say which are most effective at tackling gases caused by traffic pollution coming in through an open window. So air purifiers aren’t a perfect or complete solution to the problem of air pollution.

The government is also currently recommending that schools use HEPA (high-efficiency particulate air) air purifiers. While we hope this helps, this doesn’t change our recommendation not to completely rely on one at home. Even in a public space, an air purifier can help to improve air quality but it’s not a quick fix.

However, you can use our air purifier reviews to find one that does a great job of trapping dust, pollen and smoke particles at least.

What should I look for in an air purifier?

If you are going to buy an air purifier, some come with features that make them easier to use. These include smart features, which let you control the air purifier from your smartphone and/or check pollution levels in your home, and auto settings, which prompt the air purifier to spring into action when pollution levels rise (you’ve just sprayed deodorant, say).

The fact that an air purifier has lots of features doesn’t mean it will do a good job, by any means, so it’s important to check our reviews before you buy.

As a minimum, look for one with a HEPA filter. Other filters – including ones with names such as HEPA-type filter – aren’t held to the same European Standards as HEPA filters.

And make sure to clean and replace any filters according to the manufacturer’s instructions. A clogged-up filter won’t do much, but overly vigorous cleaning can also damage a filter.

How to improve your indoor air quality

There are steps you can take to improve your indoor air quality without spending money:

Open a window to get fresh air

As we said before, ventilation is important, and opening a window is one of the easiest way to remove polluting particles from your living space. Be strategic about this if you can and try to time it for when there isn’t likely to be lots of traffic outside if you live on a busy road.

Minimise the toiletries you’re using

Avoid sprays when buying personal care products. You may well find yourself using less hairspray, body sprays and so forth if you’re still working from home and not socialising as much as you were pre-pandemic.

Use your cooker hood

Many of us have been doing more home cooking over the past year. Switch on your kitchen hood and fans during and after cooking, even if you find them annoyingly noisy, to clear the air of oil and other ingredients that have evaporated into it, and limit damage to your walls and kitchen cabinets.

Head to our guide to improving your indoor air quality at home to find out more.

Reduce the likelihood of pollen triggering an asthma attack

Emma Rubach, head of health advice at Asthma UK, says that warm spring weather can make pollen levels spike.

Around 3.3 million people with asthma are affected by pollen, which can cause symptoms such as wheezing, a tight chest or coughing.

If that applies to you, Asthma UK says you should:

• take your prescribed preventer medicine to soothe your irritated airways, so that you’re less likely to react to the pollen trigger
• take hay fever medicines, such as antihistamines, as they stop the allergic reaction that triggers asthma symptoms and keep itchy eyes and runny noses at bay
• keep your blue reliever inhaler with you at all times in case of an emergency.

Indoor air quality for people with a lung condition

The British Lung Foundation also offers useful guidance on what people with a lung condition should do to stay safe during the coronavirus pandemic.

Zak Bond, policy officer (air quality) at the British Lung Foundation, says: ‘There’s never been a more important time for all of us to think about the quality of the air we are breathing within our own homes.

‘For the 12 million people in the UK living with respiratory condition, such as asthma or chronic obstructive pulmonary disease (COPD), it’s particularly important to minimise exposure to indoor pollutants, which can cause a flare up of their symptoms.

‘There are some simple steps we can all take to improve indoor air quality, such as keeping rooms well aired by opening windows several times a day and particularly when we are cooking or using the shower. It’s also important to keep the rooms at a comfortable temperature throughout the day to reduce the levels of moisture in the air which can result in mould.

Air purifiers have been found to reduce background concentrations of particulate matter which can trigger symptoms.’

---

This story was originally published on 26 March 2020, but has since been updated several times to reflect the latest developments.