On 1 January, Canberra experienced its worst air quality on record. Smoke from Australia’s devastating bushfires has now blown as far as Queenstown, New Zealand, forcing millions to become fluent in a new kind of jargon: AQI, PM2.5, HEPA and “hazardous”.

Since December, major retailers have reported selling out of air purifiers. Guardian Australia called JB Hi-Fi, The Good Guys and Bing Lee in Canberra on 2 January: all three appliance stores confirmed they had run out of air purifiers across the region. Road closures and uncertainty around manufacturer delivery dates mean it can be difficult to predict when more will arrive.

This is unfortunate, as preliminary product testing from consumer advocacy group Choice suggests that air purifiers can help reduce the presence of bushfire smoke in homes. “Those do work,” says Chris Barnes, who manages household product testing at Choice. “Removing smoke is one of the things that air purifiers are made to do.”

Choice have released an air purifier buying guide, and they intend to test more models over the coming months “assuming that we’re actually able to get our hands on most of those models”, Barnes says. The only unit Choice presently recommends, the Philips Blueair 205 (paywalled), costs upwards of $699. At time of checking it was sold out on Amazon and unavailable for home delivery through Harvey Norman, but was still available for purchase, with delivery, online through Bing Lee.

However, many people do not have a spare $700 to spend on white goods, and are facing hazardous air quality now, not within a four to seven day delivery window. Buying an air purifier is “maybe something to think about, at this stage, for next season – God forbid”, Barnes says. “Plan ahead.”

In the meantime, the first and most important thing you can do is follow government advice and close all your doors and windows. “Read the warnings, know when the smokey days are coming and try and seal the house again in advance,” Barnes advises.

There are some other steps you can take to help reduce the presence of bushfire smoke indoors. Sealing your home properly has a secondary benefit of making your home more energy efficient too.

Block out draughts

“Really the key is to keep [smoke] out in the first place,” Barnes says of dealing with hazardous air days. Even if your doors and windows are closed, smoke can still creep in through the gaps.

“Australian houses, by world standards, are very leaky,” Alan Pears, a senior industry fellow at RMIT specialising in clean energy and climate policy, told Guardian Australia in October 2019.

Pears recommends a very cost-effective diagnostic tool to find where air is leaking into and out of your home. “Put a bit of cling film across the bottom of a clothes hangar and just walk around near the bottom of doors and windows, around the edges of the skirting board, and see if there’s a lot of air being sucked out of or into your living area.”

Pears explains that bathrooms and laundries are the primary culprits when it comes to air leakage, because they often have fixed ventilation or ducts leading to the outside, to help prevent condensation. Simply remembering to close bathroom and laundry doors, or installing automatic door closers so you don’t have to remember, should help keep your home air-tight.

Once you’ve figured out where leaks are coming in from, “there are lots of strip-things you can put along the bottom of your door to seal [it], and there are lots of foam and rubber tubings you can put around windows to seal those up properly.” He suggests using YouTube as a resource for figuring out how to install these.

If you can’t make it to a hardware store, Barnes suggests that rolled up towels at the bottom of doors should help. While he says it doesn’t make much of a difference if the towel is wet or dry, “in principle [a wet towel] would probably help trap a little bit more smoke, but really you’re not going to get that much smoke coming in through those sorts of gaps”. A wet towel will, however, “help keep some of the heat out as well”.

Vacuum up

Air filters aren’t the only household products with filters. “The HEPA filter in an air purifier is really what does most of the work in trapping smoke particles, so if you have one in your vacuum cleaner you’re putting it through the same sort of filter,” Barnes says. “An air purifier processes the air,” he adds, so it can’t do anything about the soot particles that have already settled around your home. “Just do the vacuuming, because you probably want to get the smoke and dust and soot off the carpet and off the floors anyway.” Barnes also recommends wiping down furniture, “to try and get as much particulate out of the house as possible”. This does not mean you can flip a vacuum cleaner upside down and use it to suck in the air in your home though. This does not work.

If there’s still a lingering smoke smell once your home is sealed and tidy, all you can really do is “open your house up again when the air’s fresh again outside”.

Use air conditioning, if you have it

If your home has split-system air conditioning installed, you should already be running it with a sealed-up home. Although air conditioner filters are designed mostly to catch dust and other larger particles, Barnes suggests that “they may well help” with haze too.