Experts warn against opening your windows when using an air purifier — and what you can *actually* do when temperatures soar

Knowing whether air purifiers work with windows open is a common dilemma, especially as the weather warms up. After all, it's natural to want to let fresh air into your home throughout spring and summer.

However, the downsides of cracking open the windows to combat higher temperatures is the rise in pollen, dust and airborne pollutants. This is where the best air purifiers can be a real life-saver as they can help with allergies and generally improve air quality at home.

So, this leaves us wondering – do air purifiers work with windows open, or is it counter-productive? And if they struggle to keep up with outdoor pollutants, are air purifiers worth it during the summer months when you're more likely to have the windows open? I consulted the experts and asked them to weigh in and settle the debate.

Do air purifiers work with the windows open?

While it may seem like air purifiers are simple appliances, there are many things I wish I'd known before buying an air purifier, including how to use them properly. And although I now know I should leave an air purifier on while cleaning, I've always questioned, 'do air purifiers work with windows open?'

The short answer is yes – but there are some caveats. The general consensus among the experts is that while most air purifiers will still work with windows open, it's not ideal.

'Air purifiers can still function when a window is open, but they may not be as effective,' warns Dyson engineer Shawn Navarednam.

This is because the air purifier may struggle to keep up with the constant influx of outdoor particles, such as pollen, dust, and pollution – which makes it trickier if you're trying to pollen-proof your home.

Katie Lilywhite, air treatment expert at AO.com echoes this; 'Your air purifier will work when the windows are open, however it will be far less efficient. These appliances rely on circulating and filtering the air in enclosed spaces and face an uphill struggle when windows or doors are left open.'

So, what should you do?

Noel Fok, CEO and co-founder of EcoAir, explains that while opening windows is essential for maintaining good indoor air quality, it is best to turn your air purifier off while windows are open.

'It will have to work harder to remove outdoor pollutants from the new air coming in and this can affect overall performance,' he says. In fact, you may find that your air purifier will go into overdrive and ultimately cost more to run.

'Ideally, open windows - and doors - in various rooms for 5-10 minutes each day to create airflow and refresh the air in your home and then, once windows are closed, turn your air purifier back on so it can get to work purifying the refreshed indoor air,' Noel recommends.

That being said, it's not a major issue if you do want to open the windows for brief intervals while your air purifier is running, believes Shawn from Dyson.

'If ventilation is needed for comfort or safety, keeping the window open for short periods is fine, the purifier will still help clean the air, but it could be at a slower rate,' he advises.

So, while your air purifier can still work with windows open, for best results you should switch it off while you ventilate the room if you want to maximise its efficiency.

There is another solution worth considering, though, and that's investing in a combined air purifier-fan. As air purifiers don't cool a room, these hybrid appliances will cool the room and at same time filter out airborne pollutants. This makes them a smart choice for warmer months when keeping windows shut isn't always practical.

Shop the best air purifier fans

FAQs

Do air purifiers work if the door is open?

Air purifiers do work with the door open, but it's worth noting that their effectiveness will be greatly reduced.

'If the door is open, untreated air keeps flowing in, so the purifier cannot fully clean the space,' says Chris Michael, chair of Meaco.

'It will still filter the air that passes through it, but it will not be able to keep on top of the whole room. You will get much better results with the door closed so the air stays contained and the purifier can do its job efficiently.'

That said, if you prefer to keep internal doors open – particularly when it's warm – being mindful of where you place your air purifier can help. Positioning it deeper into the room you want to target will ensure it's filtering the air where it's most needed.

Where should you not put an air purifier?

Air purifiers also work best in locations with maximum movement or air – for example, close to windows, doors or walls.

'Avoid placing it behind furniture or under shelves, where airflow is restricted, or near radiators where extreme heat may damage the machine. These spots can block the circulation of air, making it harder for the purifier to clean the whole room,' warns Shawn from Dyson.

You also need to make sure that there's around 3-5 feet of clear space around the air purifier so that it can work to the best of its ability and maintain constant airflow.

Do air purifiers work in an open room?

Whether an air purifier works in an open room is a difficult one, as it's not a simple answer.

'They can help, but not as effectively as in a closed space,' says Chris from Meaco. 'New air keeps coming in, so the purifier has more to deal with. You just need to make sure you get one that’s powerful enough for the size of the space.'

The experts agree that for larger, open spaces, opt for a more powerful model with a decent Clean Air Delivery Rate (CADR) – which measures the volume of air the air purifier can filter, or clean, in a given timeframe.

Alternatively (and budget dependent), you might want to place two air purifiers at opposite ends of the room to help clean air circulate throughout.

So, will you be keeping your windows open or closed this summer? If you want your air purifier to work to the best of its ability, it's best to keep them closed.