The Best Air Purifiers for Allergies

It wins because it is the least compromised machine in the table. 229 certified smoke CADR clears the 200 CFM AHAM asks for a 300 square-foot room, it does that on 31 watts — $34 a year — and ENERGY STAR measures its ozone emission at 0.00 ppb because there is no ionizer to emit any.

The filter classification is the detail worth noticing. The register records it as HEPA, not HEPA-Type, which several better-marketed machines in this table do not manage including two sold under “True HEPA” branding. What that distinction means.

It is not the most powerful machine here and it is not the largest. It is the one where every column reads well and none of them has an asterisk.

265 certified smoke CADR across 410 certified square feet, which clears AHAM’s 267 CFM threshold for a 400 square-foot room. AHAM classifies it fan-and-filter — no ion generator — and ENERGY STAR measures 0.00 ppb on the identically-rated AT40.

Winix’s far better-known 5500-2 has lower certified output, ships PlasmaWave, and uses 31% more electricity a year. The AT41 is the newer machine and it is better on every axis except availability.

435 certified smoke CADR and 674 certified square feet is the largest genuine coverage here, and 9.0 CFM per watt is the best efficiency figure in the whole table. For a genuinely large space nothing else is close.

The reason it is not the overall pick, and the reason we can be exact about it: AHAM classifies this model as carrying an ion generator while ENERGY STAR records it as fan-and-filter and measures 2 ppb ozone. The registers disagree, and rather than choosing the flattering reading we print both. Two parts per billion is far under the 50 ppb program limit and is not a health concern for most people — but it is not zero, and several machines here are.

16 watts. $17 a year. Certified for 169 square feet, comfortably clearing the 107 CFM AHAM asks for a 160 square-foot bedroom, with 0.00 ppb measured ozone and a HEPA-classified filter.

A bedroom purifier is only useful if it is still switched on in six months, which makes noise and running cost the real specification. This one is cheap enough to forget about.

231 certified smoke CADR, ENERGY STAR verified, 0.00 ppb measured ozone, no ionizer, $43 a year. Genuinely good numbers, and it is stocked essentially everywhere, which is not nothing.

One caveat and one correction. The caveat: ENERGY STAR classifies the filter HEPA-Type despite the True HEPA branding. The correction: LEVOIT advertises 1,718 square feet of coverage and the certified figure is 358. Both numbers appear on LEVOIT’s own page — the first is coverage at one air change per hour, the second at AHAM’s 4.8 — and only the second describes air purification as you would recognize it.

370 certified smoke CADR across 574 certified square feet, and the most useful thing Alen publishes is the filter interval: 12–15 months for the standard filter and 7–10 months for the carbon variants, at 24/7 operation. Almost nobody in this category publishes intervals qualified by duty cycle.

It has a switchable ionizer, and Alen publishes the ozone figure both ways — zero when disengaged, under 0.001 ppm when engaged. ENERGY STAR measures 1 ppb. Publishing the number both ways is unusually straightforward behavior for this category and worth crediting.

Its advertised coverage of 2,800 square feet against 574 certified is the widest claim-to-certified gap on this site — nearly five times.