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Air Purifiers
Air purifiers explained — how HEPA filtration works, which size you need, and how purifiers compare with humidifiers for allergies, dust and cleaner air at home.
How Air Purifiers Work
An air purifier pulls room air through one or more filters and pushes it back out cleaner. At the heart of most models is a HEPA filter, which captures at least 99.97% of particles as small as 0.3 microns — including dust, pollen, pet dander and many airborne allergens.
Many purifiers add an activated-carbon filter to absorb odours, smoke and gases that a HEPA filter can’t catch, plus a washable pre-filter that traps larger particles like pet hair and extends the main filter’s life. Unlike a humidifier, a purifier doesn’t change humidity at all — it cleans the air, which is why many allergy-prone homes run both. Our Humidifiers vs Air Purifiers comparison explains which one tackles which problem.
What to Look For When Buying
Room size and CADR: match the purifier’s coverage to your room — the CADR rating shows how fast it cleans the air, and bigger rooms need a higher CADR.
True HEPA: choose a true HEPA filter over vague ‘HEPA-type’ claims.
Carbon filter: essential if smoke, cooking smells or pets are your main problem.
Running costs: check replacement filter prices and how often they need changing, usually every 6–12 months.
Noise: for a bedroom, look for a quiet sleep mode in the low-dB range.
Our Air Purifier Comparison
Read our in-depth comparison of humidifiers and air purifiers — what each one removes, who needs which, and when running both makes sense.
Difference Between Humidifier vs Air Purifier: Which One Should You Pick?
How do you know which is the right choice for you, a humidifier vs an air purifier for the issues…
Related Guides
More air-quality guides from across the site — our dedicated air purifier reviews and buying guides are in the works.
About Air Purifiers
Clean air and balanced humidity work together: purifiers remove particles and allergens from the air, while humidifiers and dehumidifiers control the moisture in it. If you’re unsure which your home needs first, our Humidifiers vs Air Purifiers comparison breaks it down symptom by symptom.
We’re currently researching air purifiers for this section, and full reviews are coming soon. In the meantime, explore our Buying Guides and Guides & Tips for the rest of your home’s air.