My downstairs neighbor smoked. Not occasionally — constantly. The smell drifted up through the floorboards and settled into my apartment like an unwelcome houseguest. My couch smelled like an ashtray. My clothes smelled. I tried candles, air fresheners, opening windows in January. Nothing worked.

I bought an air purifier out of desperation. I did not expect it to help much. Twenty minutes after plugging it in, the smoke smell was gone. I walked out of the apartment and back in to test it — like resetting your nose — and I could not smell anything but clean air.

What to look for in an air purifier

Not all air purifiers are the same. For smoke and odors, you need three things: a true HEPA filter for particles, an activated carbon filter for gases and odors, and a CADR (Clean Air Delivery Rate) high enough for your room size.

HEPA alone does nothing for smoke smell. HEPA traps particles — dust, pollen, pet dander. Smoke particles are small enough to pass through some HEPA filters. The carbon filter is what absorbs the volatile organic compounds that make smoke smell like smoke.

The model I bought and why

I got the Coway Airmega AP-1512HH. It is the one Wirecutter has recommended for years. About a hundred and sixty dollars. It covers roughly three hundred and sixty square feet — fine for a bedroom or living room, not enough for a whole apartment.

The pre-filter is washable — I rinse it in the sink every two weeks and it comes out gray with whatever was in the air. The HEPA filter lasts about a year. The carbon filter, which is the one handling the smoke smell, lasts about six months with heavy use. Replacement filters are about forty dollars for a set.

It has an auto mode that ramps the fan up when it detects particles and down when the air is clean. At night I run it on the lowest setting — it is quiet enough that I forget it is on. The highest setting sounds like a box fan. I only need that when I burn something in the kitchen.

The electricity cost is negligible

Running this thing twenty-four hours a day on auto mode costs me about three dollars a month in electricity. That is less than a single scented candle and a whole lot more effective.