How We Test

Every air purifier we recommend goes through the same evaluation. We start with numbers that an independent body has verified, check the product against safety and ozone rules, calculate what it will really cost you to run, and only then look at features and design. When we test a purifier in person, we publish the room, equipment, and conditions so you can judge the result.

As of September 2026, our reviews are based on manufacturer specifications, official certification databases, and published independent test data. We have not yet started in-house testing, and no review on this site claims hands-on results.

Part 1: The research-based evaluation (every product)

Step 1: Verify CADR in the AHAM Verifide directory

Clean Air Delivery Rate (CADR) is the most useful single number for comparing purifiers. It is measured under the AHAM AC-1 standard and reported separately for smoke, dust, and pollen, in cubic feet per minute. Higher is faster.

We look the model up in the AHAM Verifide directory and record the certified smoke, dust, and pollen CADR, plus the date we checked. If a brand publishes a CADR that is not in the directory, we call it a manufacturer claim. If a brand only publishes “coverage area” or an “air changes per hour” figure without a certified CADR, we say so, because those numbers depend on assumptions the brand chooses.

Two details matter:

CADR is measured on the highest fan speed. Most people run a purifier on a quieter setting, so real-world performance at night is lower than the headline number.
The two-thirds rule. AHAM recommends a smoke CADR of at least two-thirds of your room’s floor area in square feet (for an 8 ft ceiling). For wildfire smoke, AHAM recommends a CADR equal to the full room area.

Worked example. Your bedroom is 12 ft x 14 ft = 168 sq ft (15.6 m²).

Everyday use: 168 x 2/3 = a smoke CADR of at least 112 cfm.
Wildfire smoke: a smoke CADR of at least 168 cfm.
What that means in air changes: 168 sq ft x 8 ft ceiling = 1,344 cubic feet. A 112 cfm purifier moves 112 x 60 = 6,720 cubic feet per hour, which is 6,720 / 1,344 = 5 air changes per hour on its top speed.

Step 2: Check filter claims

HEPA wording. In the US, “True HEPA” usually refers to the Department of Energy definition of at least 99.97% capture of 0.3-micron particles. European H13 and H14 grades are defined under EN 1822. Terms like “HEPA-type,” “HEPA-like,” and “99% HEPA” have no standard definition, so we flag them.
Carbon. For odors and VOCs, the amount and form of activated carbon matters more than the word “carbon” on the box. We record the carbon weight when the manufacturer publishes it and note when it does not.
Claims history. We search the BBB National Programs National Advertising Division decisions and major news for challenges to a brand’s filtration claims and mention relevant outcomes.

Step 3: Ozone and safety checks

Any purifier with an ionizer, UV-C lamp, plasma, or photocatalytic stage can create ozone, which irritates the lungs. We check:

CARB certification. California requires portable indoor air cleaners sold there to be certified, with ozone emissions at or below 0.050 parts per million, and to meet an electrical safety standard such as UL 507 or UL 867. We look the model up on CARB’s official list.
UL 2998. Some products carry UL’s zero-ozone-emissions validation. We note it when present and verified.
Ozone generators. We do not recommend devices sold to deliberately produce ozone as “air cleaners,” in line with EPA guidance.

Step 4: Noise

We record the manufacturer’s decibel figure for the lowest and highest fan speeds and note where it was measured if the brand says. Because brands measure at different distances, we treat these as rough guides unless we measured them ourselves (see Part 2).

Step 5: Energy use and running cost

We record wattage by fan speed from the spec sheet, ENERGY STAR certification status, and where available the unit’s efficiency (smoke CADR per watt, the metric ENERGY STAR uses). Portable air cleaners sold in the US have also been covered by federal Department of Energy efficiency standards since December 31, 2023, with a stricter tier from December 31, 2025.

Worked example. A purifier that draws 40 W on its everyday speed and runs 24 hours a day: 40 W x 24 h x 365 days = 350,400 Wh = 350 kWh per year. At an electricity price of $0.17 per kWh, that is 350 x 0.17 = about $60 per year. Swap in your own rate from your utility bill.

Step 6: True cost of ownership

We add the purchase price, yearly filter cost, and yearly electricity cost, then show the total over five years.

Worked example. Purifier price $220. Replacement filter $60, changed every 12 months. Electricity $60 per year.

Year 1: $220 + $60 = $280 (first filter included in the box)
Years 2 to 5: 4 x ($60 filter + $60 power) = $480
Five-year total: $760, or $152 per year.

A cheaper purifier with a $90 filter every six months can easily cost more than this over five years.

Step 7: Real-world owner reports

We read long-term owner reviews and independent test reports for problems a spec sheet will not show: rattles, sensor drift, app failures, filter availability, and warranty service. We cite independent testers by name when we use their data.

Step 8: Score and rank

For buying guides, we rank products on a consistent weighting:

Factor	Weight	What we look at
Verified performance	35%	AHAM Verifide CADR relative to the use case and room size
Cost of ownership	20%	Five-year cost including filters and electricity
Safety and transparency	15%	CARB listing, ozone risk, honest HEPA and coverage claims
Noise	10%	Low and high speed dB, sleep mode
Features and usability	10%	Sensors, auto mode, filter indicators, app
Brand support	10%	Warranty, filter availability, claims history