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.Air quality monitorsPM2.5, CO2, VOCs, radon. Which sensors are real measurements and which are estimates.Wildfire smokeSmoke is part particle and part gas. What to run before, during and after an event.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 US standard for a HEPA filter is 99.97% capture at 0.3 microns. H13 is a grade in the separate European EN 1822 scale. "HEPA-type" and "HEPA-like" are unregulated marketing terms with no test behind them. Look for a stated standard, not a suffix.
Advertised room size is not usable room size
A box claiming 1,560 sq ft is usually quoting two air changes an hour. For allergies or smoke you want four to five, which roughly halves it. Coway rates the Airmega 400 at 3,120 sq ft at one air change and 1,560 at two, from the same machine.
Start with CADR, then stop
Clean Air Delivery Rate is the one figure certified by a third party, so sizing starts there. It is not the whole decision: noise decides whether you actually run the unit, and carbon mass decides whether it touches smoke and VOCs at all.

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

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