Australia is choking on smoke – so are air purifiers the answer?

Martin Farrer

The smoke haze that has hung over large parts of New South Wales since November has prompted people to rush out and buy air purifying machines to try to keep the smoke at bay in the their homes.

The advice from the government is to shut your doors and windows and stay inside, especially if you have pre-existing respiratory issues. Nevertheless, demand for air purifiers has been so great that shops are reporting that they are running out.

Galvan Cheung at Good Guys in Alexandria in Sydney said stores had very few left.

“We are almost completely sold out across the range from every manufacturer,” he said. “Our regular suppliers can’t guarantee stock of air purifiers until next year. Unless you are willing to drive to Coffs Harbour or Port Macquarie – they are the only stores that have any stock. Stocks are low in every state because they’ve all had problems with bushfires.”

Related: Will wearing a face mask protect me from bushfire smoke? – explainer

But what features should you look for in buying one and do they even work?

What does an air purifier do?

These are electrical devices that work by plugging into the mains socket. They filter the air that’s coming into your house and take out the harmful toxins and microparticles and then help blow the clean air around the home. They are not the same as humidifiers or air conditioners.

What should I be looking for?

Experts agree that you must make sure your device has an HEPA filter (it stands for high-efficiency particulate air). It works by pushing the air through a fine mesh that then collects harmful particles such as pollen, dust mites, tobacco smoke and, crucially for Australians, bushfire smoke.

Chris Barnes, the household product expert at Choice.com.au, said a HEPA filter was vital for trapping harmful smoke.

“A HEPA filter is something which is important to trap fine particles,” he said. “Smoke does tend to be fine particles so you need a really, really good filter. You might have to do a bit of maintenance by taking the filter out and cleaning it every few weeks.

“You should check that you can clean the filters because if you need to replace them with new ones every time the cost can mount up.”

It’s also important that the purifier has a fan that can blow the fresh air around the house or around the room you’re trying to clean.

“You must have good air flow around the purifier because otherwise it will just sit there and clean that corner of the room,” Barnes said. “The better units will typically have their own fan but you can give it a helping hand by using a pedestal fan to blow the air around.”

Some also come with a carbon filter but that was not as important as the HEPA filter.

What’s on the market?

Cheung says that Good Guys sell four brands – DeLonghi, Dyson, Cli-mate and Breville. You can pick up a desktop device for about $70 but they become progressively more expensive depending on how big the space is and how sophisticated you want your technology to be.

The Dyson Pure Hot+Cool purifying fan heater sells for around $900 and, as the name suggests, is also a mini aircon unit. It claims to be able to simultaneously heat or cool a whole room while advanced purifiers remove fine particles such as allergens and pollutants. Dyson says it can purify the air in an 81 square metre room. It also comes with an app which you can use to monitor air quality levels in your home.

Another popular machine in Australia is the Arovec air purifier which sells for $168.99 on Amazon. It claims to neutralise dust via a preliminary filter, eliminate cooking and smoking smells and filter unhealthy air.

The website 10reviews.com.au rates the US-made Levoit LV-H132 machine, which retails at around $140, as one of the best domestic devices. Amazon.com.au is currently sold out of these machines. Another highly recommended one is the Germ Guardian, made by another US company, Guardian technologies, which is almost $700.

Do they actually work?

Experts agree broadly that air purifiers do help to keep harmful air particles out of your home. But as with any consumer choice, it depends on how much you want to pay. Barnes says that Choice has been working on a product review of air purifiers and taking advice from its UK sister organisation, Which?

Related: NSW fires: wind change expected to fan bushfires as Sydney smoke causes hazardous air quality – live

He said it was probably worth paying a bit extra to get a more expensive machine.

“Which? found that the real cheapies didn’t really do the job particularly well,” he said.

Dr Christine Cowie, a respiratory health expert from the Centre for Air Pollution, Energy and Health Research and the Woolcock Institute of Medical Research, told Guardian Australia last week air purifies could help.

“There are a few studies that indicate air purifiers are useful in reducing particulate matter indoors but they do need to be fitted with a Hepa filter,” Cowie says.

Be aware that every purifier has a set amount of area it can purify. “One small air purifier will not do a whole house,” Cowie says.

NSW Health was more sceptical in its response to Guardian Australia.

“Air purifiers can reduce particles in a smaller indoor area such as a single room that is closed off from other areas, however there is limited evidence of their effectiveness during bushfire smoke events.”

Does aircon do the same job?

If you have a reasonably up to date split aircon unit it will help to keep the air inside your home cleaner because it will have a good filtration system.

“Because you close up the house anyway when you are using your air conditioning and the indoor units have a filter, it will have some effect,” Barnes said. “The more recent units have better filtration systems so if you have reasonably up to date one it is better than nothing.”