A large twin-intake tower Coway rates at 328 cfm smoke CADR. Its headline 3,120 ft² is quoted at ONE air change per hour; at AHAM's 4.8 the comparable figure is about 508 ft².
Pros
Cons
Verdict
The Airmega 400 is a well-built large-room machine with the clearest ionizer answer on this site — CARB classifies all four SKUs Mechanical, so California's certifier found nothing capable of generating ozone. It publishes noise, wattage, dimensions and weight, and its pre-filters are washable. The problem is the number everyone quotes. Coway's 3,120 ft² is at one air change per hour, and it publishes nothing at AHAM's 4.8 convention; run its own CADR through AHAM's own arithmetic and you get about 508 ft². That is still a large room, and it is six times less than the box implies. Add that the CADR itself is Coway's own — no Coway model appears in the AHAM directory at all — and this is a machine you buy on its build and its certification rather than on measured performance.
Price, seller and package contents change. Check the variant on Amazon before you buy.
Who it's for
Who should skip it
How this coverage figure is stated
⚠️ THIS IS THE NUMBER TO READ CAREFULLY ON THIS UNIT, and we have not used Coway's headline.
Coway publishes two bases, and neither is the one that makes purifiers comparable: "1 air change/hour 3,120 ft²" and "2 air changes/hour 1,560 ft²". AHAM's convention is 4.8 air changes an hour, and Coway does not publish a figure at it.
The 508 ft² above is AHAM's own arithmetic applied to Coway's own CADR: smoke CADR x 1.55, or 328 x 1.55 = 508. That is the figure to use when comparing this machine against anything else on this site. The 3,120 ft² on the box is the same machine measured six times more generously.
The input is still Coway's own CADR, not a measured one — see below.
Always compare two purifiers at the same air-change rate; manufacturers pick different ones and the headline square footage is not otherwise comparable.
| CADR (manufacturer-stated) | 328 smoke / 328 dust / 400 pollen Coway's own figures; no AHAM entry found |
|---|---|
| Coverage at AHAM's 4.8 basis | About 508 ft², calculated as 328 x 1.55 Coway does not publish a figure at this basis |
| CARB | Certified, device type Mechanical, notified 2026-01-13, executive order G-26-006 |
| Noise | 22–52 dB(A) |
| Maximum power | 66 W |
| Filters per service | TWO Max2 filters and TWO pre-filters one of each per side |
| Coverage as Coway states it | 3,120 ft² at 1 air change/hour; 1,560 ft² at 2 air changes/hour |
|---|---|
| Dimensions | 14.8 x 22.8 x 14.8 in |
| Weight | 24.7 lb |
| AHAM Verifide | No Coway model appears in the October 2023 AHAM directory |
| Smart control | None on the 400. Wi-Fi and app control are the 400S |
Our calculation, not the manufacturer’s
| Air changes | When you want this rate | Room it suits |
|---|---|---|
| 4.8×/hour | Wildfire smoke, allergy season, a room you are sensitive in | 513 ft² |
| 4×/hour | The rate most allergy guidance assumes | 615 ft² |
| 2×/hour | General freshening in a room without a specific problem | 1230 ft² |
Worked from the CDC/NIOSH relation
air changes = (CADR × 60) ÷ (area × ceiling height),
assuming an 8 ft ceiling. Change the ceiling height and these
numbers change. AHAM’s own consumer rule — a smoke CADR of at
least two-thirds of the room’s area — puts the ceiling for this
unit at about 492 ft², which is the same arithmetic
at roughly five air changes an hour.
This CADR is the manufacturer’s own figure, not an AHAM Verifide
measurement, so treat it as a claim rather than a verified result.
You can check this at home. In a closed room of the size in the first row, PM2.5 should halve about every nine minutes at top speed once its source stops. A monitor shows whether this unit manages that in your home. How to run the test
Ionizer and ozone
None identified by California's certifier. CARB's complete certified list carries four rows for this family, all Mechanical:
· Coway | Airmega 400(G) | AP-2015F(G) | Mechanical | 2026-01-13 | G-26-006 · Coway | Airmega 400(W) | AP-2015F(W) | Mechanical | 2026-01-13 | G-26-006 · Coway | Airmega 400S(G) | AP-2015E(G) | Mechanical | 2026-01-13 | G-26-006 · Coway | Airmega 400S(W) | AP-2015E(W) | Mechanical | 2026-01-13 | G-26-006
Under California's regime only ELECTRONIC air cleaners are tested against the ozone emission limit, because only they have a component capable of producing one. A Mechanical classification means CARB did not identify an ion- or ozone-generating stage. Coway's product page does not mention an ionizer, UV lamp or plasma stage either.
That is a real point of difference from the Blueair units on this site, which are classified Electronic because HEPASilent charges particles electrostatically. If you want filtration and nothing else, this machine is on the right side of that line.
| Capability | What it needs | Status |
|---|---|---|
| Particle and carbon filtration | Two Max2 filters, pre-installed | Included |
| Washable pre-filters | Two, one per side | Included |
| Replacement filter set | Airmega 400/400S Max2 Filter Set — two filters, sold separately | Sold separately |
| Replacement pre-filters | Sold separately AND singly; the machine needs two | Sold separately |
| Air quality sensor with Auto mode | Built in | Included |
| Wi-Fi and app control | Not on the 400 — that is the 400S | Not verified |
| Independently measured CADR | Not available — no AHAM entry found | Not verified |
Package contents vary by variant and seller. Check what is in the box on the Amazon listing before you buy. “Not verified” means the manufacturer does not document it either way — not that it is missing. “Not offered” is the other thing: the manufacturer does document it, and the answer is that this model does not have it.
Coway Airmega 400 Max2 filter set
Part 3104756 / AP-2015-FP / ⚠️ "Max2" IS A FAMILY NAME, NOT A PART. Coway sells an Airmega 250 Max2 filter and an Airmega Icon Max2 filter as separate products. Searching for "Max2" on its own will show you filters for machines that are not yours. · "Filter Life Expectancy is 12 Months", per Coway's product page for the set. Coway does not publish an hours-per-day assumption behind that figure on this page, so it cannot be scaled arithmetically to your own use. Note also that the interval applies to the Max2 element; the pre-filter is a separate part with its own maintenance, and being washable it is the one that costs nothing to look after.
Checked against the AHAM Verifide directory, CARB's certified air-cleaner list and the manufacturer's own pages. We did not test this unit. Nothing here is a measurement of ours: every figure is either documented by the manufacturer or published by an independent standards or testing body, and where the two disagree this page says so.
Blueair
AHAM Verifide at 353 cfm smoke CADR for a 550 sq ft room, and Blueair publishes exactly those numbers rather than a flattering pair — which almost nothing else in this catalogue does. It draws 4 W on its lowest speed.
Blueair
AHAM Verifide at 283 cfm smoke for a 439 sq ft room, and the rare case where the electrostatic question has an actual number attached: ENERGY STAR measured its ozone emission at 2 ppb.
Blueair
A compact tower with an AHAM Verifide smoke CADR of 123 cfm and a 190 sq ft AHAM room size. CARB classifies it Electronic, which is a consequence of how Blueair's HEPASilent works rather than a fault.
