Clean Air Home Lab

Start with CADR, not the advertised room size

Most air purifiers are sold on a room-size number measured at two air changes an hour. We size them at the rate you actually need, price five years of filters, and tell you which models are still made.

  • AHAM-certified CADR
  • Five-year filter cost
  • Every spec cited and dated
  • No manufacturer sponsors

What are you trying to fix?

Start from the problem. Each of these goes straight to the buying decision, not to a category index.

Air purifiersSized by CADR against your real room, not the box claim. Bedrooms, large rooms, open plan.BedroomsQuiet picks for sleep. Sorted by the maker's sleep-mode noise figure and by room size.Large roomsOpen plan and big living rooms. Picks with enough CADR for the real floor area.Purifiers under $100Small-room units that still use a real HEPA filter, with the yearly filter cost.Air quality monitorsPM2.5, CO2, VOCs, radon. Which sensors are real measurements and which are estimates.Wildfire smokeSmoke is part particle and part gas. Picks with a real HEPA filter and real carbon.Filter replacement costsThe expense nobody prices in. Real intervals and annual cost by brand and model.Allergies and petsPollen, dust mites and dander are large particles. Why a washable pre-filter saves money.Damp basementsSizing a dehumidifier, pump versus gravity drain, and which 50-pint models are still made.Radon testingThe EPA action level is 4 pCi/L. How to test, what mitigation costs, finding a certified pro.HVAC filtrationMERV explained, filter sizing, and when a furnace filter beats another portable unit.

Three things the box gets to say that nobody checks

Air purifier marketing leans on three phrases that sound like specifications and are not.

"True HEPA" and "HEPA-type" are not the same claim
The EPA says a HEPA filter, as the US Department of Energy defines it, can in theory remove at least 99.97% of airborne particles 0.3 microns in size. Words like "HEPA-type" or "HEPA-like" do not make that claim. Look for the word HEPA and what the maker says it means.
Advertised room size is not usable room size
Makers quote room size at different air change rates. Coway rates the Airmega 400 at 3,120 sq ft at one air change an hour and 1,560 at two, from the same machine. So size by CADR instead. The EPA chart asks for a CADR of 65 for a 100 sq ft room with an 8-foot ceiling.
Start with CADR, then stop
Clean Air Delivery Rate is the figure AHAM Verifide certifies, so sizing starts there. It is not the whole decision. Noise decides whether you will run the unit. And the EPA says CADR is for particles only. For gases, it says carbon works when a large amount is used.

How we get to a recommendation

Sized by CADR

Sized by CADR, not by box claims

We size purifiers by Clean Air Delivery Rate at a stated air change rate, so the coverage figure means something.

Read the CADR guide
Filter cost reviewed

Five-year cost, not sticker price

Filter cost is calculated from the manufacturer's own price and replacement interval, never estimated.

See filter costs
Research backed

Every number has a source

Specifications are cited to manufacturer documentation or AHAM, with the date checked. We do not physically test products.

Read the methodology

Sources and last review

Specifications on this page are taken from the documents below, on the dates shown. We do not physically test products; read our methodology. Page last reviewed .

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