Best Air Purifiers for Allergies

Match the AHAM smoke CADR to your room: CADR should be at least two-thirds of the room's square footage for about five air changes an hour (a 300 sq ft bedroom needs roughly 200 CADR). Makers' "coverage" numbers often assume fewer air changes; our cards list the CADR and the rated coverage separately.

True HEPA (H13) captures 99.97% of 0.3-micron particles and every purifier here has it or equivalent. What differs is how much air moves through it (CADR), how loud that is, and whether there is enough activated carbon to do anything about smoke and cooking smells — thin carbon "pre-filters" do little.

More than the purifier, often. Five years of filters ran from about $150 (Levoit Core 300S) to about $400 (Blueair 211i Max) in our pricing, plus $30–$80 a year in electricity on medium. Our running-cost figure includes both.

A sealed 400 sq ft room, an incense stick burned for five minutes to raise PM2.5 above 300 µg/m³, then the purifier on high while a laser particle counter logs the drop; we time to 90% reduction. We repeat on the highest fan setting that measures under 50 dB at 1 m, measure watts on medium, and price the maker's filters over five years at the recommended interval.