Your questions on air purifiers answered
What is the best air purifier?
The Dyson hushjet compact purifier is the best air purifier I’ve tried. After testing most of Dyson’s air purifiers over the past five years – including some of its much larger fan models – this is easily the most impressive small-format option I’ve tried. It combines fast, effective purification with genuinely useful smart features, low running costs and a distinctive, design-led finish that feels a cut above many compact rivals.
If you’re looking to spend less, the Coway airmega 50 is tidy and inexpensive but effective in most rooms. If you’re working with a larger, open-plan area, Coway’s airmega 350 is also well worth considering. It doesn’t have the same level of app control or detailed data as Dyson, but it’s powerful, responsive and covers a lot of ground with minimal fuss.
How I tested air purifiers
During my at-home trials, I monitored air quality at regular intervals and created a few deliberately messy real-world scenarios to see how each machine coped with what you might encounter in everyday life. That meant throwing puffs of flour and wood ash into the air, burning matches like a pyromaniac, and lighting candles to create smoke.
Yes, there was a spreadsheet involved, along with a few carefully crafted formulas to work out which purifiers were actually doing the best job according to the following key metrics.
- Air purification: I used an independent air quality monitor to measure real improvements in air quality rather than relying on whatever numbers the purifier itself decided to report. Where a purifier had an auto mode, I used it; otherwise, I stuck with the medium fan speed for consistency.
- Noise: Using a decibel meter, I measured noise levels at different fan speeds. The best air purifiers were quiet enough to run overnight without disturbing sleep.
- Ease of use: I assessed how straightforward each purifier was to set up and operate, including the performance of smart features such as companion apps, built-in air-quality monitoring, scheduling tools and automated alerts.
- Design: Air purifiers usually sit out in the open, so I also considered how each model looked in a living space. The best designs balance practicality with aesthetics, while remaining appropriately sized for the rooms they serve.
- Value for money: Finally, I considered not just the upfront cost but the long-term investment, including replacement filter prices and the estimated cost of running the purifier day-to-day.
What does an air purifier do?
Professor David Fairen-Jimenez, head of the absorption and advanced materials lab at the University of Cambridge, says: “We spend so much time indoors that the quality of the air will impact the quality of health and life.” Air purifiers filter out various particles and pollutants to improve air quality.
The contaminants could be anything from volatile organic compounds (VOCs) generated from doing work around the house (if, for example, you have freshly painted walls) to car fumes coming in through your windows when you air your home, or the fumes that result from frying food.
How do air purifiers work?
Most work by drawing the air into the machine and running that air through a filter (sometimes several filters) to grab small particles of pollen, pollution, dust and – depending on the type of filter – viruses and smaller particles. It then sends the clean air out into the room again. Some also use something called ultraviolet germicidal irradiation to ‘kill’ any viruses caught in the air.
It’s worth noting it isn’t only catching small particles that’s tricky, but also PM 2.5, or fine particulate air pollution, which is another area researchers are continually looking into.
Do air purifiers remove dust?
In a word: yes. The thing to know about air purifiers is that their efficacy depends largely on the filtration system and the size of the particles they can capture. The gold standard in filters is the high-efficiency particulate air filter (aka the HEPA filter), which captures at least 99.97 per cent of 0.3-micron and larger particles. The naked eye can’t see particles smaller than 10 microns in size, so, yes, most air purifiers will remove dust from the air.
Do air purifiers help with allergies?
If your allergies are triggered by pollution or other fine particles in the air, a good purifier is likely to help.
Studies carried out by Lung India show that asthma patients who were sensitised to dog and cat fur, dust mites, and birch and tree pollen found symptoms improved after 10 weeks of sleeping in a room where there was a purifier containing a HEPA filter.
That said, even the best one has limitations – you will still be breathing in allergens when you leave your home and open windows – but, on the whole, if you notice your house being clean and ventilating well reduces allergies, it’s safe to assume an air purifier will also have a positive effect.
Can air purifiers help remove smells?
A good air purifier can help reduce or even eliminate unpleasant smells entirely, while making the air you breathe healthier and fresher.
Do air purifiers help with mould?
While air purifiers won’t help treat active mould in your home, they can help capture spores from the air, preventing them from reproducing and spreading throughout your home, so these gadgets are a great way to control the spread of airborne mould particles.
Read more: Air purifiers vs dehumidifiers – which one your home needs, according to experts
What is the clean air delivery rate?
The CADR (clean air delivery rate) indicates how quickly the purifier removes contaminants from the air, but it shouldn’t be the sole factor in deciding which one to choose. It’s advised to aim for a CADR that is at least two-thirds of your room size in square metres. For example, if your room is 20 sq m, opt for an air purifier with a CADR of at least 240 cubic metres per hour.
Why you can trust IndyBest reviews
I’ve been testing air purifiers since 2021 for a range of consumer and lifestyle publications. Over the past few years, I’ve developed a reliable testing process designed to cut through marketing claims and measure what actually matters: how well each purifier cleans the air and how quickly it does it.
Our expert tester, Joanne Lewsley, has been testing air purifiers and other air quality appliances for more than a decade, so she knows exactly what makes for a good air purifier. She has consulted experts on what to look out for, and all of her reviews are based on independent opinion and real-life testing.
The wider IndyBest team also reviewed individual air purifier models, such as Dyson’s purifier. Additionally, our experts have given in-depth insight on other air-quality-related items, such as dehumidifiers, air fresheners and humidifiers. These gadgets can also be used for other chores, such as drying clothes in a more energy- and cost-effective way.
Meet the experts
Henry Burridge: Associate professor in environmental fluid mechanics, Imperial College London.
Professor David Fairen-Jimenez, head of the absorption and advanced materials lab at the University of Cambridge.
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