Air Purifiers

Frequently asked questions

What CADR do I need for my room?

For an 8-foot ceiling, start with smoke CADR equal to at least two-thirds of the room's square footage. A 12 x 14 bedroom is 168 sq ft, so the baseline is about 112 cfm. Add more headroom for smoke, high ceilings, open layouts, or if you want to run the purifier quietly.

Why use smoke CADR instead of a brand's maximum room claim?

Smoke CADR is a comparable particle-cleaning rate measured in cubic feet per minute. Room claims often use different air-change assumptions, so a huge coverage number can be misleading. CADR is the better first filter when comparing models.

Does HEPA remove odors and VOCs?

HEPA-style particle filtration helps with dust, pollen, dander, and smoke particles. Odors and gases need activated carbon or another gas-removal medium. A thin carbon layer can help a little, but it is not the same as a deeper carbon bed.

Should an air purifier run all night?

Usually yes, especially in a bedroom. Air cleaning depends on fan speed and run time, so a purifier that stays quiet enough to run continuously is often better than a louder model you turn off.

How should I adjust for a high ceiling?

Multiply the room area by ceiling height divided by 8 before applying the CADR rule. A 200 sq ft room with a 10-foot ceiling should be treated like roughly 250 sq ft.

Is a tiny purifier enough for allergies?

Only in a very small space near you, like a desk, dorm corner, or bathroom. For a normal bedroom, a tiny purifier is usually underpowered compared with a full-size bedroom model.

How we grade

We score every product on the criteria that actually decide the purchase.

PickGrade grades air purifiers on five weighted criteria: clean-air delivery for the room (30%), particle filtration (20%), noise at usable speeds (18%), odor and carbon capability (16%), and filter cost and maintenance (16%). Two things are worth understanding about these grades. First, we prefer AHAM-verified CADR figures, and we mark a purifier down when its airflow number is manufacturer-supplied or estimated rather than independently verified. Second, the grade measures a purifier's absolute capability, not whether it's right for you. That means a small, correctly-chosen desk unit will score low here and still be exactly what you should buy for a desk, which is why our grades and our recommendations don't always point at the same product. The Levoit Core Mini is the clearest example: a modest grade, and still the right $50 purchase for a personal space. Fit is what the quiz and the buying guides are for. We do not claim hands-on lab testing; recommendations rest on manufacturer data, AHAM and independent measurements where they exist, and buyer-fit tradeoffs.