COWAY Air Purifier for Home Up to 1,748ft², HEPA Filter for Smoke, Allergies, Pet Dander, Odor, Air Quality Monitor, Auto&Eco Mode, Timer, Filter Indicator, 3yr Warranty, Mighty AP-1512HH, Black

Why it's worth it

The Coway AP-1512HH Mighty pairs true HEPA filtration with a sensor that ramps the fan when the air gets dirty. It's compact enough for a bedroom, quiet enough to leave on, and it doesn't ask you to think about it once it's plugged in.

The auto mode is the reason to buy this one. A pollution sensor watches the room and raises fan speed when particle levels climb — when pollen counts spike, when the dog flops down beside it, when someone's cooking. You don't have to notice a problem to get more filtration. That matters, because the most common way people undermine a purifier is by leaving it on low and forgetting about it.

Four stages, sequenced so the expensive one lasts longer. A washable pre-filter grabs hair and coarse dust first. A deodorization layer handles odors and VOCs. Then air reaches the true HEPA filter, which captures 99.97% of particles at 0.3 microns — the range that covers pollen, pet dander, dust mite debris and mold spores. Keeping the big stuff off the HEPA element is what stretches its life through a full year of running.

From our review of 12 air purifiers for allergies, by David Sinclair, Managing Editor

What we like

• +The auto mode is the reason to buy this one
• +Four stages, sequenced so the expensive one lasts longer
• +Eco Mode saves you money on a machine you'll run constantly
• +It fits where you need it

What to know

• –There's no app and no Wi-Fi
• –The Bipolar Device is an ionizer, and asthma patients should switch it off
• –Filters are an annual expense you shouldn't ignore