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.
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.
Pros
Cons
Verdict
The Blue Pure 411 Auto is one of the few genuinely small purifiers with an independently measured CADR: AHAM puts it at 123 cfm smoke and sizes it at 190 sq ft, and that room figure reconciles exactly with AHAM's own arithmetic. The washable fabric sleeve is a real advantage, because the stage that loads fastest is the one you can maintain for nothing. Two things to understand before buying. CARB classifies it Electronic — it passed the ozone test, but the electrostatic charging stage is how HEPASilent works and cannot be switched off. And Blueair publishes no noise figure or wattage for it at all, which on a unit designed to run continuously is the specification you would most want.
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), which corresponds to 4.8 air changes per hour. 123 x 1.55 = 190.65 and the directory prints 190. A third-party figure, not a manufacturer claim.
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 | 123 cfm, AHAM Verifide |
|---|---|
| AHAM suggested room size | 190 sq ft (equivalent to 4.8 air changes per hour) |
| CARB | Certified, device type Electronic, notified 2020-11-24, executive order G-20-192 |
| Filter life | 6 months of operation, signalled by a red indicator |
| Replacement filter | Blue Pure 411 Series Particle + Carbon Filter shared with the 411 and 411+ |
| Dust CADR | 107 cfm, AHAM Verifide |
| Pollen CADR | 96 cfm, AHAM Verifide |
|---|---|
| Meets AHAM ozone limits | Yes |
| Filter indicator reset | Hold the centre button 7–10 seconds, up to 30 depending on model |
| Pre-filter | Washable fabric sleeve, specific to the Auto and sold separately |
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 | 192 ft² |
| 4×/hour | The rate most allergy guidance assumes | 231 ft² |
| 2×/hour | General freshening in a room without a specific problem | 461 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 185 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 THAT NEEDS EXPLAINING RATHER THAN ALARMING. CARB's complete certified list carries "Blueair | Blue Pure 411 Auto | 3231101000 | Electronic | 2020-11-24 | G-20-192".
Electronic does not mean the machine is an ozone generator. It means California's certifier identified a component capable of producing ozone and therefore TESTED it against the state's emission limit — and it passed, which is what certification means. Blueair's HEPASilent works by charging particles electrostatically before filtering them mechanically, so the classification follows directly from how the technology works. AHAM's directory separately marks this model Yes in its "meet ozone limits" column.
What it does mean practically: this is not a filtration-only machine in the way a CARB-Mechanical unit is, and the charging stage is integral to how it filters rather than a feature you switch off. If you specifically want no electronic stage at all, this is not that machine. Every 411-series variant on the CARB list is classified the same way.
| 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 sensor | Built in; it is what distinguishes this variant | Included |
| Replacement cartridge | Blue Pure 411 Series Particle + Carbon Filter, sold separately | Sold separately |
| Published noise figure | Not published by Blueair | 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 411 replacement filter
Part "Blue Pure 411 Series Particle + Carbon Filter" · "6 months of operation", signalled by a red filter replacement indicator on the unit. Blueair does not publish an hours-per-day assumption behind the figure, so it cannot be scaled arithmetically — but on this range the indicator is doing the counting, and Blueair's stated approach on the sister 511 model is that its algorithm tracks fan speed, running time and measured pollution rather than days. After fitting a new cartridge the indicator has to be reset by hand: Blueair's instruction is to press the centre button for 7 to 10 seconds, and up to 30 seconds depending on the model.
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.