← All guidesGuide · FiltersFilter types, decoded.
The filter is the product — everything else is a fan and a box. Four terms cover nearly every purifier on the market, and only two of them deserve your money.
- The baselineTrue HEPACaptures 99.97% of particles at 0.3 microns — pollen, dander, dust mite debris, most smoke. The minimum acceptable standard for allergies and asthma.
- The marketing trap"HEPA-type" / "HEPA-like"No standardized efficiency — these can capture as little as 50% of fine particles. If the box won't say "True HEPA," assume it isn't.
- The odor specialistActivated carbonHEPA catches particles, not gases. For cooking smells, pet odor, VOCs, and wildfire smoke gases you need a substantial carbon bed — measured in pounds, not a thin sprayed mesh.
- The one to skipIonizers & ozoneIonizers and "plasma" features can emit ozone, a lung irritant. If a unit has one, make sure it can be switched off — and that the unit is CARB certified either way.
What the index actually uses
Filter types across the 113 models we track. True HEPA dominates — but "HEPA-type" still slips in, so check the label on every model page.
True HEPA9 models · 8%
True HEPA H139 models · 8%
H13 True HEPA6 models · 5%
Unspecified5 models · 4%
HEPASilent2 models · 2%
HEPASilent particle + activated carbon2 models · 2%
Match the filter to the problem
Next stepSee which models use which filters.
Filter type is listed on every model page, alongside replacement cost and lifespan.