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Do air purifiers really work?

Our expert take on what they can and can't do, and whether they're worth your money.

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Last updated: 23 February 2022
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Checked for accuracy by our qualified fact-checkers and verifiers. Find out more about fact-checking at CHOICE.

Need to know

  • Air purifiers are growing in popularity and there are a huge range of brands and types available
  • Air purifiers can help clear the air of bacteria and viruses such as COVID-19, but they do have their limitations
  • CHOICE experts review more than 40 air purifiers from brands such as Dyson, Breville, Kmart and more, scoring them for how well they remove smoke, dust and other irritants from the air and how easy they are to use. Become a CHOICE member to access full reviews

As we learn to live with a heightened awareness of airborne viruses such as COVID-19 and look for ways to clear the air in our homes, schools and workplaces, air purifiers are growing in popularity.

They're billed as an easy way to improve air quality and reduce pollution, and there's a huge variety of brands, sizes and types available at a wide range of prices. 

Some boast sleek designs and impressive-sounding features, from virus-zapping UV lights to activated carbon filters and Wi-Fi connectivity. Plus, there's a whole host of acronyms you've probably never heard of – HEPA, CADR, VOC – what? 

In a new take on futuristic fashion, there's even an air purifier you can wear like a necklace (spoiler: studies indicate that most of these are not very effective, and they could be largely useless in the open air; you'd be better off just wearing a mask). 

So, can air purifiers actually benefit your health – improving air quality to reduce bacteria and the risk of viruses, for example? Can they lessen the effects of bushfire smoke and other irritants such as dust, pollen and chemicals? Or are they just another useless fad? 

Here, CHOICE household products expert Chris Barnes takes us through what they can and can't do.

What can an air purifier do?

It can help remove pollution such as dust and smoke

Smoke from back-burning or bushfires is a reality of living in Australia and can be very irritating or even damaging for asthma sufferers and people with other health conditions. 

"Yes, a good air purifier can help clear the air of smoke from bushfires or tobacco, and odours, but you should look for a product with a HEPA filter, which is a filter that traps very small particles," says Barnes. "It's one of the most important features of an air purifier – not all purifiers on the market have this, so make sure you check the product specifications."

Look for a product with a HEPA filter, which traps very small particles ... It's one of the most important features of an air purifier

CHOICE household products expert Chris Barnes

The HEPA filter may be used in conjunction with another type of filter such as carbon, charcoal, ionisation or UV filter, and all have different key uses and effectiveness. For more on different types of filters to look out for, read our air purifier buying guide

Air purifiers can also help remove common household allergens, such as dust, pollen and mould, that can trigger hay fever, asthma and other respiratory conditions. In our expert air purifier reviews, we give individual performance scores for how well each model removes smoke, dust and volatile organic compounds (VOCs) from the air, so you can check each model's performance against your specific concerns before you buy.

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A good air purifier can help clear the air of smoke from bushfires or tobacco, and odours, but you should look for a product with a HEPA filter.

It can help clear the air of viruses such as COVID-19, bacteria and mould spores 

While we'd all love a magic COVID-busting appliance in our homes, air purifiers aren't the perfect solution. But they can be useful. 

Viruses such as the COVID-19 virus are usually transmitted by small aerosol particles when an infected person breathes out or coughs or sneezes. These tiny droplets can stay in the air for a long time, up to an hour or more.

In the right circumstances, a good air purifier can remove most of these particles from a room's air.

An air purifier with a HEPA filter can be surprisingly good at trapping viruses and bacteria out of the air

CHOICE household products expert Chris Barnes

"An air purifier with a HEPA filter can be surprisingly good at trapping viruses and bacteria out of the air," says Barnes. "The issue is that it can only process what's in the air that it happened to suck in at the time, so it wouldn't necessarily process all the air in your home to trap and kill a virus that may be present. 

"But, in addition to following health advice such as regularly washing your hands, an air purifier might be worth considering as an extra protection against airborne viruses if you have people coming and going in your house, such as kids going to school or essential workers, or if it's hard to keep your home freshly aired."

We don't test the ability of air purifiers to kill viruses in our labs, but you can read more in Do air purifiers trap viruses and other germs?

It can tell you about your indoor air quality

Most air purifiers have sensors to determine how much pollution is in the air around them, along with other measurements such as indoor air temperature and humidity. 

Usually they'll display this information on the unit or (for Wi-Fi-connected models) in an associated app, perhaps as a detailed particle count or a simple coloured indicator (such as green for good through amber and to red for heavily polluted air). 

It can be very interesting – and useful – to see just how much dust or smoke is in your home's air, and the sort of activities that add to pollution, particularly if you're sensitive to these types of irritants.

Simply frying food on a gas cooktop can rapidly create a lot of pollution in the air

For example, simply frying food on a gas cooktop can rapidly create a lot of pollution in the air (even when you don't burn the food!). 

Spraying insecticide, using cleaning fluids and painting will also add chemicals and fine aerosol particles to the air. 

Leaving the purifier to run on automatic, so that it adjusts its speed to suit the level of pollution, can be useful too, as hearing it rev up can be an indication that there's smoke or other pollution getting into your home. 

What can't an air purifier do?

It can't keep your home free of germs

While an air purifier can be very good at filtering out germs, it can only filter the air in the room that it's in. Air in other parts of the house can remain untreated. And any virus-laden droplets that settle onto surfaces won't end up going through the air purifier.

So it's still very important that you keep up the usual hygiene practices: washing your hands, cleaning hard surfaces, and of course, trying to avoid bringing germs into your home in the first place. 

It can't guarantee frequent air changes in your home

Ideally the air in a room should be replaced by fresh air several times an hour, to prevent the build-up of carbon dioxide, odours, moisture and other pollutants.

The simplest way to do this in most cases is through natural ventilation: opening doors and windows and letting in the breeze. When that's not possible, such as in small rooms with poor ventilation, or when the outdoor air is too hot or cold, or too smoky, then an air purifier will certainly help. But it's unlikely to achieve the same level of air change in the long term.

Ideally, the air in a room should be replaced by fresh air several times an hour

If you often need to keep your home closed up, or if it's just very well sealed with no air leakage from windows and doors, then a mechanical ventilation system might be a solution. These usually include air filters to make sure incoming air is free of dust and other nasties.

It can't reliably filter out dangerous chemicals

We test air purifiers for their ability to remove volatile organic compounds (VOCs). These are typically released into the air from paint, furniture, aerosol sprays, cleaning products and so on. 

They include a wide range of chemicals which can cause breathing and skin irritation, headaches and worse. Common culprits are formaldehyde, ammonia, benzene and acetone (we use acetone in our tests).

Although some air purifiers are specifically designed to remove such chemicals, most are not very effective, and several are pretty useless at this particular task. 

And... you'll still need to dust your home

Sadly, however good the air purifier is at removing dust from the air, there's always more that settles on the furniture and the floor. Dusting, vacuuming and mopping will still be a necessary chore.

Is it worth buying an air purifier?

Whether an air purifier is worth buying and how much you should spend depends on things such as what you'd like to use it for and the effectiveness of the product you buy.

"We've reviewed a range of air purifiers from different brands, ranging in price from $89 to over $1600," says Barnes. 

"We measure the Clean Air Delivery Rate (CADR) of each air purifier to assess how well it clears particles of dust, smoke and other volatile organic compounds (VOC) from the air, and use that information to give each model a score based on its performance and ease of use." 

We are seeing some disappointing products in our labs, some which barely clear anything from the air

CHOICE household products expert Chris Barnes

"The performance of different brands and types of air purifiers definitely varies and we are seeing some disappointing products in our labs, some which barely clear anything from the air," he says. 

"How well a model will perform in your home can be affected by things such as its relative size to the size and shape of the room you're using it in, as well as how many, and which, pollutants are in your air." 

How to choose the right size and capacity

Size really matters when it comes to air purifiers. Our experts recommend you look especially closely at the advertised Clean Air Delivery Rate (CADR) and consider the size of the room you'll be using it in. 

Most models will advertise what capacity room they're suited for. You basically want to ensure that the air purifier works hard enough – or has a CADR that's high enough – so it circulates the full volume of air in your room to clean it thoroughly, otherwise it won't be doing the job you bought it for. 

Generally, the higher the CADR the better, but keep in mind this standard is tested using very specific settings (with the purifier unit placed in the centre of the room and set to its highest speed), and it only relates to the removal of three pollutants: dust, tobacco smoke and pollen. 

It may be worth getting a model that's rated for a slightly larger room than you need

Barnes suggests it may be worth getting a model that's rated for a slightly larger room than you need. 

"That can mean the purifier will clear the room's air faster on its highest setting, but still comfortably keep the air clear on its lowest and quietest speed (good for when you're trying to sleep)."

Find out more about CADR and the Dyson-specific test method known as POLAR, in our air purifier buying guide.

Ongoing filter costs

If you're considering buying an air purifier, make sure you take into account the cost of replacement filters, which can add up quickly.

Costs vary between brands and models, and replacement filters for the models we've tested can range from about $55 to $89 each, which could add up to well over $100 per year depending on how often you run your purifier and at what setting. 

Check our air purifier reviews for filter prices and estimated annual costs on models we've tested.

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