How we pick
This page is the site. Everything else is an application of what is written here — including the part about where the method stops working.
Every competitor in this category competes by claiming more testing. Of the seven roundups we read while planning this site, four make first-person testing claims and not one of those claims is independently checkable. We cannot win that contest honestly and we are not going to try.
What we compete on instead is arithmetic you can re-run. Every ranking on this site is derived from inputs that are published by somebody other than us and somebody other than the company selling the machine.
The selection criteria, in order
1. Certified Clean Air Delivery Rate
The first filter, and the one that does most of the work. We look for a CADR figure in one of two public registers:
- AHAM’s VERIFIDE directory — AHAM retains an outside laboratory to test sample units and verify manufacturers’ claimed ratings under ANSI/AHAM Standard AC-1.
- EPA’s ENERGY STAR database — certification requires testing to the same AC-1 standard through an EPA-recognized certification body, and the database additionally publishes measured ozone emissions and certified annual energy use.
A unit in neither register can still appear on this site, and it is labeled manufacturer-claimed everywhere its figures are shown. It cannot take a top-pick slot on the strength of numbers nobody checked.
2. Room size, by AHAM’s own rule
Quoted verbatim from AHAM’s published standards: “the CADR of your air cleaner should be equal to at least two-thirds of the room’s area.”
Two conditions come attached and are routinely dropped. AHAM’s suggested room sizes assume a 8-foot ceiling, and AHAM states that if your ceilings are higher, an air cleaner rated for a larger room will be necessary. And the figure on the certification seal is based on cleaning and circulating the room’s air 4.8 times per hour — not the one air change per hour that produces the much larger number on the box.
For pet households we size to 6 air changes an hour rather than 4.8, because the allergen source is continuous. That is our judgment applied to AHAM’s method, and it is labeled as ours wherever it appears rather than presented as a standard.
3. Total cost to run
Certified annual energy use in kWh per year, from whichever register lists it, multiplied by 18.34 cents per kWh — the U.S. average residential price for June 2026 from the EIA’s Electric Power Monthly, Table 5.3. The rate is printed on every page that shows a dollar figure so you can substitute your own.
Filter cost is the other half and is far less well documented. Where a manufacturer publishes both an interval and a price we compute the annual figure. Where they publish one or neither, the page says so. We do not estimate an interval to complete a table.
4. Filter classification, as recorded rather than as marketed
The registers classify a unit’s filter as HEPA or HEPA-Type. That is a published field and it does not always agree with the packaging — several machines sold as “True HEPA” are recorded as HEPA-Type. We report the register’s classification. What the distinction means.
5. Ionizer status and measured ozone
Every product card on this site states whether the unit has an ionizer, plasma or UV stage, whether it can be switched off, and its measured ozone emission where a register publishes one.
The exclusions, stated as exclusions
- A non-defeatable ionizer disqualifies a unit from being a top pick on any asthma-scoped page.
- No published CADR, no top-pick slot. A unit with no CADR figure at all cannot be ranked and does not appear.
- Manufacturer-claimed CADR cannot win a roundup over a certified unit of comparable output.
What we do not do — and what we do instead
We do not test air purifiers. We do not own them. We have no laboratory, no particle counter, no test chamber, and no staff beyond the person writing this.
We are saying that in the same breath as what we do instead, because the two belong together: we compile third-party certified CADR, apply the published sizing standard out loud, compute running cost from certified annual energy use at a stated electricity rate, read ionizer status and measured ozone off the register rather than the box, cite primary sources for anything touching health, and exclude on EPA guidance.
Every one of those inputs is public. You can check any of them in about a minute, and you can reach a different conclusion from the same evidence — which is not true of a testing claim.
Where our method is weak
This section is not optional and it is not softened. These are the real limits of what we do.
| Limitation | What it means for you |
|---|---|
| CADR is not a pet-dander test | The standard uses smoke, dust and pollen. No certification for pet allergen exists. CADR is the best comparable number available and it is a proxy. |
| Certified figures are measured on a new filter | In a sealed chamber, at maximum fan speed. Your filter will be older, your door will open, and you will run it on low. |
| No per-speed CADR is published by anyone | Our 'buy headroom so it runs quiet' advice is reasoning from certified maxima plus how fans work. It is sound and it is not a measurement. |
| We cannot assess build quality or reliability | That needs owning units over years. We do not, so we say nothing about it rather than repeating other people's impressions. |
| Filter intervals are optimistic in pet households | Manufacturer figures assume general use. A shedding dog shortens them and nobody publishes by how much. |
| The registers sometimes disagree | AHAM and ENERGY STAR classify some Blueair models differently on ionizer status. We print both rather than choosing the flattering one. |
| Carbon mass is almost never published | Odor performance scales with it, and we can only report the filter composition a register records. That is weaker evidence than a weight. |
How to check us
Every figure on this site links to its source. If you want to verify a whole page rather than a single number, these are the four places everything comes from:
- AHAM VERIFIDE directory of certified room air cleaners — search by brand.
- ENERGY STAR certified room air cleaners — includes measured ozone and annual energy use.
- EPA’s Guide to Air Cleaners in the Home — the source of every ozone and efficacy statement we make.
- AAFA / Allergy Standards certified product register — where we mention that certification.
If a figure here is wrong, or a model has been discontinued or re-rated, tell us and we will correct the page and mark the correction.
Who does this
One person, writing under the name Scooter M., who is genuinely interested in this category and does the arithmetic. No credentials are claimed because none are held. More about that, and the editorial policy that governs corrections.