Clean air delivery rate: Commonly referred to as CADR, this is a combination of how much air they move and how clean they can get that air. It might seem like a lot, but you want the air in a room to circulate at least three times per hour. “If you’re in a conversation in a room and that air is only being cleaned once or twice every hour, then the HEPA system is not going to be very effective,” said Dr. Sai Nimmagadda, an allergy & immunology specialist in Chicago. He says to consider airplanes, which completely change the cabin air every three minutes, or 20 times per hour.
HEPA filters: There is only one filter you want: a HEPA, or high-efficiency particulate air, filter. Anything that says “HEPA-like” or something along those lines means you should immediately look for a different product. HEPA filters will grab upwards of 99.9% of fine air particles, including viruses, bacteria and pollen. These filters aren’t cheap. Depending on use, they may only last six months before needing a replacement, so make sure you factor this in when pricing out your options.
Pre-filters: A screen housed within an air purifier that traps larger air pollutants—like dust or pet dander—so that they don’t clog up the HEPA filter, which is meant for the microscopic crap. These are almost always washable, so that you don’t have to constantly buy replacements.
Carbon filters: Another air purifier filter, which is apt at taking care of volatile organic compounds, or VOCs, aka the stinky stuff. Odors from cooking, cannabis and/or pets (or to be more technical, molecules like nitrogen dioxide, acetaldehyde and sulphur dioxide) are now trapped.
Coverage: Air purifiers are broken down by “coverage” or the largest room they can effectively clean, typically circulating the air two to five times per hour. This ranges from small kitchens to large family rooms, so break out the tape measure. In general, it’s better to have several small air purifiers in multiple rooms, rather than one large one for the entire house.
Where should I put my air purifier?
“You can’t put a small HEPA filter in the corner of the room expected to protect you when you’re on the other side of the room,” says Nimmagadda. For best results, place it in the room you spend the most time in, like your bedroom, and make sure it can circulate air effectively throughout the room, and that it’s not obstructed by pieces of furniture or hidden away in a corner.
What about allergies?
If you want to specifically keep one room clean from, say, pet dander, make sure to keep the room relatively sealed tight with an air purifier running before you enter. Nimmagadda recommends focusing on your specific allergies. For instance, if you’re allergic to tree pollen, keep windows closed in the springtime.
But unless there’s serious air pollution outside, you don’t want to keep your windows permanently closed as fresh air is important for air quality. “One of the theories of why asthma and other [respiratory] illnesses are on the rise is because these [new] homes that we build are so airtight that they don’t really have fresh air exchanges. That leads to more indoor air pollution,” says Nimmagadda, who explains that’s why smoke from poorly ventilated kitchens or dust mites in your carpet are so prevalent.
Do air purifiers protect you from Covid-19?
According to recent studies, “air filtration simulation experiments quantitatively showed that an air cleaner equipped with a HEPA filter can continuously remove SARS-CoV-2 from the air.” While companies are hesitant to make broad claims about Covid prevention, some have their air purifiers independently tested, like Coway, which showed a “99.98% removal of Covid-19 in under two minutes.” This effectiveness is especially good news with the upcoming winter season. Then again, the virus is spread through person-to-person contact, so if you’re sitting two inches away from someone who has the virus, that air purifier isn’t doing anything to stop you from getting infected.
Best Overall Air Purifier: Blueair Blue Pure 311 Auto
CADR: 250 for smoke, 250 for dust, 244 for pollen
For Room Sizes: 388 square feet
Noise Level: 23 to 53 decibels
Filter Price: $40
Filter Lifespan: 6 months