The clean-air home · 2026
CADR, air changes per hour, what the carbon stage really does and which replacement filter actually fits your unit. Researched from manufacturer documentation and published standards — and we say plainly when something is not documented.
By the NestyFinds editorial team · Researched from manufacturer documentation, manuals and the AHAM Verifide directory · not bench-tested
An air purifier pulls room air through a filter and pushes it back out with fewer particles in it. That is the whole mechanism, and everything worth comparing sits in four numbers: how much clean air it delivers (CADR), how many times an hour it can do that to your room, what the filter media actually is, and what the replacement filters cost you every year. We work from the manufacturer’s own documentation and the AHAM Verifide directory. We do not test units in a lab, so you will not find a performance figure here that someone did not publish first.
Reviewed in detail
Winix
A 4-stage tower air purifier - permanent pre-filter, washable AOC carbon filter, a filter stage Winix calls True HEPA, and a switchable PlasmaWave ionizing stage - AHAM Verifide for 370 sq ft at 4.8 air changes per hour.
BEST DOCUMENTED Coway
The Coway Airmega Mighty AP-1512HH is a 12.3 lb portable room air purifier that Coway rates at 361 sq ft (4.8 air changes per hour) using a washable pre-filter, an activated-carbon deodorization filter, a filter Coway labels True HEPA, and a bipolar ionizer stage that has its own on/off button.
MOST MEASURED OUTPUT Honeywell
A two-stage mechanical purifier that holds three Type R "True HEPA" filters behind one Type A pre-filter, AHAM Verifide at 300 cfm smoke CADR with a 465 sq ft AHAM suggested room size.
Indicator gone red?
Most returns happen because the part number was one character off. Each guide lists the exact OEM numbers, the models it fits, and the near-identical models it does not.
Before you compare models
The one number that lets you compare two purifiers directly: how much clean air the unit delivers, measured for smoke, dust and pollen. Look for AHAM Verifide — it means an independent lab measured it rather than the brand claiming it.
Coverage claims are not comparable until you know the air-change rate behind them. The same machine can be sold as 1,500 sq ft at one air change per hour or 350 sq ft at five. For allergies or smoke you want the higher rate, so read the small print, not the headline.
"True HEPA" refers to a defined efficiency standard. "HEPA-type", "HEPA-like" and "99% HEPA" are marketing phrases with no standard behind them. If the listing avoids the plain term, that is information.
HEPA media captures particles. It does nothing for smells, cooking odours or VOCs — that is the carbon stage, and how much carbon is in there varies enormously. A thin carbon-coated sheet is not the same as a packed carbon cartridge, and it saturates far sooner.
Some units add an ionizer, plasma or UV stage. California requires air cleaners sold there to be CARB certified, which caps ozone emission. Check whether the extra stage can be switched off, and whether the model appears on the CARB list at all.
A purifier only works while it is running, and people turn off the ones that are loud at the speed they actually need. Compare the decibel figure at the speed that matches your room size, not at the lowest setting.
The sticker price buys the machine once; the filters are the ongoing cost. Work out the yearly filter bill before you compare two units — a cheaper purifier with expensive proprietary filters can cost more over three years.
They solve different problems. A purifier moves particles out of the air; it does not lower humidity, and damp is what mould needs. If your issue is condensation or a musty smell, humidity control comes first.
It depends on whether you have a particle problem you cannot remove at the source, and that is worth being honest about. A purifier moves airborne particles through a filter; it does nothing about the source itself. If the smell is damp, the answer is humidity, not filtration. If it is a gas cooker, extraction and an open window do more than any unit on this site. Where a purifier does earn its place is with particles that keep arriving and cannot be stopped — pollen through open windows in spring, wildfire smoke, dust from a nearby road, cat or dog dander in a flat. Start with the source; a purifier is what you add when the source is outside your control.
CADR is Clean Air Delivery Rate: how much particle-free air a unit delivers per minute, measured separately for smoke, dust and pollen. It is the only figure that lets you compare two purifiers directly, because it combines how well the filter captures with how much air the fan actually moves. A superb filter behind a weak fan gives a poor CADR. The number matters most when an independent body measured it: AHAM Verifide means a laboratory did. A CADR with no AHAM entry is the brand’s own figure, and nobody outside the company has checked it.
Because a coverage figure is meaningless without the air-change rate behind it, and manufacturers pick different ones. The same machine can be sold as "1,051 sq ft" at one air change per hour or "219 sq ft" at 4.8 — both true, same unit, numbers that differ by a factor of five. AHAM’s convention is 4.8 air changes an hour. On every review here we print the basis next to the number, and where the manufacturer does not publish one we say so instead of quietly assuming.
No, and the label is weaker than it looks. There is no public certification a manufacturer can obtain for a consumer air purifier: every HEPA claim on a box is the maker’s own. AHAM’s directory lets brands declare their own filter class, and the same directory carries entries reading "HEPA-Type" next to others reading "True HEPA" or "H13". That is why every HEPA mention on this site is attributed to whoever said it, rather than stated in our own voice.
It is the legal minimum, not a feature. Since 2010 California has required portable indoor air cleaners sold or shipped into the state to be certified, which caps ozone emission. Almost every unit worth buying has it, so its presence tells you little. What is worth knowing is its ABSENCE, or a mismatch between the model on the listing and the model on the certified list — which is a real thing that happens, and something we check for each review.
That is the running cost, and it is the part of the price that is not on the price tag. Manufacturers state intervals between roughly 6 and 12 months, but the interval always rests on a usage assumption — hours per day, at what speed — and that assumption is the part most listings leave out. Our filter guides print the interval together with the assumption behind it, and say which stages are washable and which are not, because a washable pre-filter is one fewer thing you have to keep buying.
