Air purifiers can come with several types of filters and many models include multiple filter types. Not all filters are created equal.
HEPA filters. High-Efficiency Particulate Arresting (HEPA) filters are considered to be the most effective filters at targeting common allergens. HEPA filters remove at least 99.95% of allergens and pollutants.
Activated carbon filters. These filters use activated charcoal to clear smoke, chemicals and odours from the air. However, they don't filter allergens and bacteria and need to be replaced frequently.
Ozone filters. This filters can help remove odours, including the smell of smoke, but they don't remove allergens or pollutants.
Ionic filters. Ionic filters use an electrical field to remove pollutants from large areas. While they are somewhat effective, they produce ozone, a type of pollutant, and release it into the air.
Ultraviolet (UV) filters. UV filters can kill bacteria. However, in order to work, most bacteria need to be exposed for an extended period of time – much longer than most purifiers allow.
How to compare air purifiers
When choosing an air purifier, consider the following factors:
If the purifier is too large for your room, your energy bill will be unnecessarily high. If it's too small, it will be ineffective. Look for one that matches the footprint of the rooms you want to use it in. If you have a large, open space, you might need to get multiple purifiers and place them on opposite ends of the space.
An air purifier that can automatically check the air quality of the room and adjust settings accordingly will allow you to set it and forget it. Otherwise, you'll have to manually adjust the settings throughout the day.
Some air purifiers sound like a loud tower or pedestal fan, while others have a quiet hum similar to a refrigerator. To be the most effective, the air purifier should run all day, so look for a model that's quiet enough not to be a nuisance.
You'll need to replate the filters regularly. Activated carbon filters need to be replaced more often than other filter types (typically around once every three months). Filter prices can range from around $20 up to $200 or more. Consider buying replacement filters when you buy the purifier to avoid additional shipping costs.
Filter replacement indicator
Some models include an indicator or light that tells you when you need to replace your filter and can help you avoid using your air purifier while it's not working.
If you plan to keep the air purifier in your bedroom, look for a model with a sleep setting that shuts off any lights and maintains a quiet fan setting while you sleep.
A sensor light can tell you what the air quality is as soon as you enter a room.
Antimicrobial agents can stop mould from growing within the air purifier and extend the life of the filters.
Look for a purifier with multiple, adjustable fan speeds to save energy and avoid unnecessary noise.
Three tips for air purifier maintenance
Check out our top tips to get the most out of your air purifier:
Replace the filters regularly. While replacement filters add significantly to the lifetime cost of the air purifier, a purifier without working filters is effectively useless. Make sure to replace the filters at the recommended times, which is between three to twelve months for most filter types.
Consider where to put it. If you work from home or spend most of your time at home, a purifier in your office or living space can make a lot of difference. If you're out of the house a lot, a unit in your bedroom will have a more significant impact. It might be more convenient to move the purifier from room to room, so look for one that's light enough to carry. Alternatively, consider getting multiple units – one for each room.
Keep it running. In order to be the most effective, the purifier should be turned on as much as possible – with all windows and doors closed.
Sarah Brandon is a senior writer at Finder. She has a degree in Psychology from New York University and loves learning about why people do what they do. Sarah has researched and written about a wide range of topics, from pool fences to private jets to personal loans. But no matter the subject, her number one priority is figuring out what information our readers need to make the best decisions.
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