Coway
Airmega 400
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.
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.
Pros
Cons
Verdict
The Blue Pure 211+ Auto is the best-evidenced large-room unit on this site. AHAM measured it at 353 cfm smoke CADR and sized it at 550 sq ft, and Blueair publishes those same numbers instead of a bigger figure at a gentler air-change rate — which, after fifteen filter guides and eight reviews spent untangling coverage claims, is worth saying plainly. It draws 4 W on its lowest speed at 23 dB, so running it continuously is genuinely cheap and quiet. Two caveats, and neither is a defect so much as a thing to know: CARB classifies it Electronic because HEPASilent charges particles electrostatically, which is integral rather than switchable; and its replacement filter is Auto-specific, with Blueair itself warning that fitting the non-Auto version reduces CADR and voids the warranty.
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
AHAM's own suggested room size, derived from the smoke CADR by AHAM's published rule (smoke CADR x 1.55) and therefore equivalent to 4.8 air changes per hour. 353 x 1.55 = 547 and the directory prints 550.
WHAT MAKES THIS UNIT UNUSUAL: Blueair publishes 550 ft² too. It is not quoting a larger number at one air change per hour and burying the comparable one, which is what most of this catalogue does. The figure on its own page is the third-party figure.
AND IT SAYS SO IN PLAIN WORDS. Blueair's own listing states the unit "filters the air at a rate of approximately 4.8x an hour (or about every 12.5 minutes) in a 550 ft² room", alongside "up to 2640sqft extra-large spaces in 60 minutes on high". Naming the air-change rate next to the room size is the thing this whole site keeps asking manufacturers to do, and here one of them simply does it.
Always compare two purifiers at the same air-change rate; manufacturers pick different ones and the headline square footage is not otherwise comparable.
| Smoke CADR | 353 cfm, AHAM Verifide and Blueair publishes the same figure |
|---|---|
| AHAM suggested room size | 550 sq ft (equivalent to 4.8 air changes per hour) |
| CARB | Certified, device type Electronic, notified 2021-01-26, executive order G-21-017 |
| Noise | 23 dB on the lowest speed no louder than 56 dB on the highest |
| Power | 4 W on the lowest setting, up to 38 W on high |
| Replacement filter | Blue Pure 211+ Auto Particle + Carbon Filter ⚠️ AUTO-SPECIFIC, see the filter guide |
| Dust CADR | 347 cfm, AHAM Verifide |
|---|---|
| Pollen CADR | 380 cfm, AHAM Verifide |
| Meets AHAM ozone limits | Yes |
| Energy Star | Rated |
| Air intake | 360-degree, so placement is less constrained than on a single-intake unit |
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 | 552 ft² |
| 4×/hour | The rate most allergy guidance assumes | 662 ft² |
| 2×/hour | General freshening in a room without a specific problem | 1324 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 530 ft², which is the same arithmetic
at roughly five air changes an hour.
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
CLASSIFIED ELECTRONIC, AND THE REASON MATTERS MORE THAN THE LABEL. CARB's complete certified list carries "Blueair | Blue Pure 211+Auto | 3631101000 | Electronic | 2021-01-26 | G-21-017".
Electronic does not mean ozone generator. It means California's certifier identified a component capable of producing ozone and therefore TESTED the unit against the state's emission limit — and it passed, which is what certification means. Blueair's HEPASilent charges particles electrostatically before filtering them mechanically, so the classification follows from how the technology works rather than from a bolt-on feature. AHAM's directory separately marks this model Yes in its meet-ozone-limits column.
Practically: the charging stage is integral, not a switch. If you specifically want a purely mechanical machine, CARB lists every Blueair 211 and 411 variant as Electronic, and the Coway and Levoit units on this site as Mechanical — that is the comparison to make.
| Capability | What it needs | Status |
|---|---|---|
| Particle filtration | Particle + Carbon cartridge, pre-installed | Included |
| Odour reduction | Activated carbon layer, part of the same cartridge | Included |
| Washable pre-filter | Fabric sleeve — check whether one is supplied with your unit | Not verified |
| Auto mode with particle sensor | Built in; it is what distinguishes this variant | Included |
| Replacement cartridge | Blue Pure 211+ Auto Particle + Carbon Filter, sold separately | Sold separately |
| App or voice control | Not available on this model | 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.
Blueair Blue Pure 211+ Auto replacement filter
Part "Blue Pure 211+ Auto Particle + Carbon Filter" · ⚠️ BLUEAIR DOES NOT STATE AN INTERVAL ON THIS FILTER'S PRODUCT PAGE. Checked 14-sep-2026. Its subscription option defaults to six months, which is a shipping cadence rather than a measurement, and we are not going to present it as the manufacturer's stated filter life. What Blueair does publish elsewhere in this range is how its units decide: on the sister 511 model the stated approach is an algorithm that tracks fan speed, running time and measured pollution rather than days. On a unit whose whole selling point is Auto mode, the indicator is the figure to trust, not a number from a page that does not give one.
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.
Coway
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.
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.
GermGuardian
A 22-inch tower with a UV-C lamp, rated by GermGuardian at 99 cfm smoke CADR. Its honest coverage figure is 153 sq ft — the 743 sq ft in the listings is the same machine at roughly one air change per hour.