Blueair vs Coway
The cleanest values-based choice on this site: the most efficient machines in the category against the ones with nothing bolted on.
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One trade decides it. Blueair delivers the most certified air per watt in the category — 9 CFM/W on the 211i Max — and every model we cover measures 1 to 5 ppb of ozone with an ion stage the two registers describe differently. Coway’s certified Airmegas measure 0.00 ppb with no ion stage, add washable pre-filters, and reach 894 square feet. Asthma in the house pushes you to Coway; a tight electricity budget pushes you to Blueair.
Most brand comparisons on this site come down to which register a company files with. This one does not — both brands are certified and well documented. It comes down to a genuine engineering trade, and to how much weight you put on a small number that is not zero.
The two ranges, side by side
| Model | Smoke CADR | Certified room | Air per watt | Measured ozone |
|---|---|---|---|---|
| Blueair Blue Pure 411i Max | 145 CFM | 225 sq ft | 8.2 CFM/W | 2 ppb |
| Blueair Blue Pure 311i Max | 283 CFM | 439 sq ft | 8.4 CFM/W | 2 ppb |
| Blueair DustMagnet 5440i | 216 CFM | 335 sq ft | 5.9 CFM/W | 1 ppb |
| Blueair Blue Pure 211i Max | 435 CFM | 674 sq ft | 9 CFM/W | 2 ppb |
| Blueair Blue Pure 211+ | 348 CFM | 539 sq ft | 5.8 CFM/W | 5 ppb |
| Coway Airmega 400 | 376 CFM | 583 sq ft | 6.1 CFM/W | 0.00 ppb |
| Coway Airmega 450 | 443 CFM | 687 sq ft | 6.7 CFM/W | 0.00 ppb |
| Coway Airmega ProX | 577 CFM | 894 sq ft | 10.2 CFM/W | 0.00 ppb |
Electricity costs on this page use 18.34¢ per kWh, the U.S. average residential price for June 2026 from the U.S. Energy Information Administration, Electric Power Monthly, Table 5.3. Your rate is on your bill and is probably not this one; multiply the kWh figure by your own rate and you have your number.
The trade, stated plainly
Read the fourth column and Blueair wins everything under 700 square feet. Read the fifth and it loses all of them. That is the entire comparison, and it is unusually clean because neither brand is hiding anything: both publish, both certify, and the numbers simply point in opposite directions.
Two parts per billion is a small number. The ENERGY STAR program limit is 50, and a gas stove or a laser printer will do more to a room’s air than a Blueair at 2 ppb. It is also not zero, and EPA’s standing advice is to avoid portable cleaners that intentionally produce ozone because ozone is a lung irritant. Where we land: for a living room in a household with no respiratory condition, the efficiency is worth more than the 2 ppb. For a bedroom occupied by somebody with asthma, we take the measured zero and pay the electricity.
Where Blueair wins
Air per watt, at every size it competes in. 9 CFM per watt on the 211i Max and 8.4 on the 311i Max are the second and third best figures on this site. Only the Airmega ProX beats them, and it is a much larger machine at a much higher price.
Coverage per dollar of electricity. The 211i Max certifies 674 square feet for $47 a year. The Airmega 450 certifies 687 for $71. That is 2% more room for about half as much again in running cost.
A machine built for settled dust. The DustMagnet 5440i draws through vents low on the body rather than on top, which is where household dust actually is. Nothing in Coway’s range is designed around that problem — how we rank machines for dust.
Where Coway wins
The ozone column, without exception. Every certified Airmega measures 0.00 ppb and carries no ion generator. In a nursery, a bedroom or any room with an asthmatic in it, that is the specification this site ranks first — why we rank measured ozone above output in some rooms.
Washable pre-filters on every Airmega. Coway documents one on the 400, the 450 and the ProX. Blueair documents none, on any model we cover. In a house with a shedding animal that is the part that protects the cartridge you pay for.
Published noise, and one complete filter bill. Coway publishes a dB range for every Airmega; Blueair publishes none for any model. And the Airmega 400 is the only machine on this site with both a filter price and an interval, making its annual cost $196 rather than a blank.
The top of the range. 894 certified square feet at 10.2 CFM per watt beats Blueair on both axes at once — the only place in this comparison where that happens.
The pre-filter difference, and what it costs
Coway documents a washable pre-filter on every Airmega — two of them on the 400, one per intake face, and two XL sets shipped with the ProX. Blueair documents none, on any model we cover. In a house with a shedding animal that single specification changes the filter economics more than anything else on this page: coarse hair loads a cartridge far faster than fine particulate does, and a mesh you rinse is what stands between the two.
It compounds with the other gap. Blueair publishes no filter interval or price, so a buyer cannot see the consequence of a cartridge loading early; Coway publishes both on the Airmega 400, which is why that machine’s annual cost can be stated at all — the machines that document a washable pre-filter remain a short list, and every Airmega is on it.
Neither brand earns a HEPA classification
Worth stating because both sell on filtration language. Every Blueair we cover is recorded HEPA-Type, including the DustMagnet, whose AHAM entry reads “HEPA Type and Activated Carbon”. Coway’s 450 and ProX are also HEPA-Type, and its Airmega 400 is recorded as a “Composite Filter” — not classified HEPA or HEPA-Type at all.
So on the one field where Honeywell sweeps, these two brands are level and neither is impressive. It matters less than the marketing on either box implies, because certified CADR already contains filtration efficiency — but it does mean a buyer choosing between them should ignore filtration adjectives entirely and read the airflow, the ozone figure and the pre-filter instead — what HEPA-Type does and does not promise.
What each brand tells you before you buy
Coway publishes a noise range for every Airmega — 22-52 dB(A) on the 400, 23-46 on the ProX — and Blueair publishes none for any model we cover. For a machine that will sit in a living room all evening, that is the specification most likely to decide whether it stays switched on.
On filters the gap is wider. Coway publishes a price and an interval for the Airmega 400’s Max2 set, making it the only machine on this site whose annual running cost is fully computable at $196. Blueair publishes neither figure for any model, so every Blueair on this site has half its running cost unquoted — the full table of what each manufacturer publishes.
Quick picks
The efficiency pick, the measured-zero pick, and the machine that is both if the room is large enough.
| # | Product | Best for | Certified CADR | Price |
|---|---|---|---|---|
| 1 |  Cheapest to run Blueair Blue Pure 211i Max 435 certified CFM across 674 sq ft at 9.0 CFM per watt — but 2 ppb measured. | Open-plan spaces above 500 sq ft | 435CFM smoke AHAM VERIFIDE | |
| 2 |  Measured zero, washable pre-filters Coway Airmega 400 376 certified CFM with 0.00 ppb and no ion stage of any kind. | Large rooms, verified Coway | 376CFM smoke ENERGY STAR verified | |
| 3 |  Efficient and zero at once Coway Airmega ProX 577 certified CFM at 10.2 CFM per watt, 0.00 ppb, across 894 sq ft. | The largest room one machine can certifiably cover | 577CFM smoke ENERGY STAR verified |
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The picks
Blueair Blue Pure 211i Max
Blueair · model 3613111100 (Blue Pure 211i Max)
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The most air per watt of anything here and by some distance the largest certified coverage — 674 square feet. It does carry an ion generator, which is the reason it is not our asthma pick.
435 smoke / 453 dust / 450 pollen CFM · 444 PM2.5
- Certified room size
- 674 sq ft
- Energy / year
- 256 kWh
- Electricity / year
- $47
- Air per watt
- 9 CFM/W
- Power draw
- 44 W
- Noise
- Not published
- Measured ozone
- 2 ppb
- Filter class
- HEPA-Type
- AHAM rule, 600 sq ft
- Clears it (400 needed)
Ion generator — fitted
The two registers disagree: AHAM classifies this model 'Fan Filter with Ion Generator' while ENERGY STAR records it as 'Fan and Filter'. ENERGY STAR's measured ozone figure is 2 ppb. We report both rather than picking the flattering one.
435 certified smoke CADR across 674 certified square feet at 9 CFM per watt — $47 a year, the lowest running cost of anything covering more than 600 square feet. The full record on it.
The honest con: 2 ppb measured, an ion classification AHAM records and ENERGY STAR does not, no documented way to switch it off, no published noise figure and no filter schedule.
Coway Airmega 400
Coway · model Airmega 400 (AP-2015F)
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The Coway that is actually in a certification register: 376 certified smoke CADR, 583 square feet, zero measured ozone. If you want a Coway, this is the one with third-party numbers.
376 smoke / 384 dust / 409 pollen CFM · 380 PM2.5
- Certified room size
- 583 sq ft
- Advertised coverage
- 3,120 sq ft in 60 minutes
- Energy / year
- 366 kWh
- Electricity / year
- $67
- Air per watt
- 6.1 CFM/W
- Power draw
- 66 W
- Noise
- 22-52 dB(A)
- Measured ozone
- 0 ppb
- Filter class
- Composite Filter
- AHAM rule, 500 sq ft
- Clears it (334 needed)
No ionizer — filtration only
ENERGY STAR classifies this unit 'Fan and Filter', 0.00 ppb measured ozone.
376 certified smoke CADR across 583 certified square feet with 0.00 ppb measured, no ion stage, washable pre-filters on both faces, a published 22-52 dB(A) range and a published filter price. Our full review.
The honest con: $67 a year against the Blueair’s $47 for less certified room, and ENERGY STAR declines to classify its filter HEPA or HEPA-Type at all.
Coway Airmega ProX
Coway · model Airmega ProX (AP-3522F)
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The largest certified coverage on this site at 894 square feet, and the highest air-per-watt figure we have recorded at 10.2 CFM per watt — with a measured zero on ozone.
577 smoke / 586 dust / 450 pollen CFM · 581 PM2.5
- Certified room size
- 894 sq ft
- Advertised coverage
- 4,253 sq ft in 60 minutes
- Energy / year
- 335 kWh
- Electricity / year
- $61
- Air per watt
- 10.2 CFM/W
- Power draw
- 65 W
- Noise
- 23-46 dB(A)
- Measured ozone
- 0 ppb
- Filter class
- HEPA-Type
- AHAM rule, 800 sq ft
- Clears it (534 needed)
No ionizer — filtration only
ENERGY STAR classifies this unit 'Fan and Filter' and measures 0.00 ppb ozone. Coway's specification lists no ionizing stage.
The one machine that wins both columns: 10.2 CFM per watt — better than any Blueair — with 0.00 ppb measured and no ion stage, across 894 certified square feet. The full record on it.
The honest con: a far higher price bracket than anything else here, 51 lb, no filter price published, and in a room under 664 square feet it is capacity you pay for twice.
The verdict
Common questions
Is Blueair or Coway better?
Do Blueair air purifiers produce ozone?
Which brand covers a bigger room?
Which is cheaper to own?
Sources
- AHAM VERIFIDE directory of certified room air cleaners
- ENERGY STAR certified room air cleaners database
- EPA — Guide to Air Cleaners in the Home
- AHAM — air filtration standards and the two-thirds rule
Figures were read on the dates shown against each source. If one has changed, or if we have got something wrong, tell us and we will correct the page.
Read next
- CADR & costCoway Airmega 400 vs Blueair Blue Pure 211i Max435 CFM across 674 sq ft at 9.0 CFM/W against 376 across 583 at 6.1 — and 2 ppb measured ozone against 0.00.
- CADR & costBlueair vs LEVOITBlueair wins air-per-watt by a distance. Every Blueair here also has an ion stage and a measured ozone figure; every LEVOIT reads 0.00.
- AllergiesHEPA vs ionizers vs ozone generatorsWhat EPA advises about ionizers and ozone, with published measurements for every certified unit.