An air purifier works by sucking in air, passing it though a filter that captures pollutants, and pushing the cleaner air back out into the room. Today’s best air purifiers can remove everything from dust particles and pet dander to gases from the air in your home (here’s more on what air purifiers can and can’t help with).
Different models are suited to different needs and spaces, so it’s worth taking a few minutes to figure out exactly what you need before you invest. Here are six questions to ask before buying an air purifier…
What filters are included?
Different filters tackle different particles. The most common option for particle filtering is the HEPA filter (High-Efficiency Particulate Air filter). According to EU standards, to be called a HEPA filter, it must capture at least 99.95% of particles that are 3 microns or less in size. This type of filter will help with dust, pollen, viruses and bacteria.
Some air purifiers have a carbon filter (sometimes called an activated carbon filter or charcoal filter). This is designed to absorb unpleasant odors and gases.
Those are the two most common types of filter, but more advanced models might add on filters to tackle specific pollutants. For example, Dyson’s most advanced air purifiers come with a selective catalytic oxidation filter that enables them to capture and destroy formaldehyde. This is a relatively rare addition, and this type of air purifier tends to be very expensive.
How efficient is it at cleaning air?
Different air purifiers are designed for use in different-sized spaces. The information to pay attention to is how quickly air is drawn through the filter (in cubic feet per minute) and the clean air delivery rate (CADR). A rule of thumb is that, for general use, you should look for a CADR that’s at least two-thirds of the room’s total area.
Most air purifiers come with a recommended square footage for coverage, but be wary of taking this spec at face value – you also need to know how long the purifier will take to clean the air in a room of that size. To be truly effective, a purifier needs to cycle through all the air in a room three to five times per hour.
What modes does it have?
Some air purifiers come with an auto mode that adjusts based on pollution levels. They can switch on when the quality drops below a certain standard, or boost fan speeds in response to higher pollution levels, to clear the particles quickly. There might be information to show you the room’s air quality at a glance, and you might also be able to view air quality over time, perhaps via a companion app.
Basic air purifiers won’t have these kinds of features. You’ll simply switch them on or off and adjust the fan speed manually. An auto mode prompted by an air quality sensor can help reassure you that your purifier is indeed doing something. It also means the appliance can respond to air quality changes that might otherwise be missed.
Aside from an auto mode, some air purifiers have other special modes. A common one is a sleep mode or night mode, which will typically be quieter than standard modes (and may also turn off the appliance’s lights), so you can run it while you’re asleep without it disturbing you.
How do you control it?
Pricier, more advanced air purifiers will sometimes come with a companion app. This can provide information that’s difficult to show on-screen on the purifier itself, such as air quality over time. It might also enable you to turn the purifier on or off remotely. Some smart air purifiers have voice assistant support, too.
Basic purifiers are operated by buttons on the machine itself, or may come with a remote control so you don’t need to get up and go over to the purifier to switch it on.
The ability to set a timer or schedule when your air purifier comes on is useful if you don’t want to just be running it constantly.
How do I keep an eye on the filters?
In order for your air purifier to keep doing its job efficiently, the filter(s) will need washing or replacing periodically. Premium purifiers can have a filter health section in the companion app, while more basic options just have a warning light that tells you when your filter’s time is up.
Before buying, consider how often the filters will need replacing, whether they can be washed, and how expensive replacements are.
Can it do anything else?
Some air purifiers can also be fans, heaters, dehumidifiers, or humidifiers. Or, perhaps more accurately, air purification is occasionally a bonus function added to other kinds of devices. For appliances that work by sucking in air and blowing it out again, you can just add a filter and – hey presto! – you’ve got an air purifier. In these cases, the air purification is often not the priority, so don’t expect advanced features like air quality sensors or stats.
However, it can be a great way to save money and space by combining what could be multiple appliances into one. For example, some of the best fans on the market – including a number of Dyson fans – also operate as air purifiers. These can be a great option for people who suffer from seasonal allergies.
