Coway Airmega ProX Review
The biggest certified portable machine we can find, read against the register rather than the brochure. We do not test units; this is the record, including the column where it underperforms.
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The largest certified coverage we can find on a portable machine, and — unusually — also the most efficient: 577 certified smoke CADR across 894 certified square feet at 10.2 CFM per watt, for $61 a year. It measures 0.00 ppb with no ion stage and has the quietest published top speed of any large machine here. The asterisks: a pollen column below its own smoke figure, a filter price nobody publishes, and a 51 lb footprint.
First, the disclosure that shapes everything below: we have not tested this unit. We own no air purifiers and run no laboratory. What follows is the ENERGY STAR record plus Coway’s own published specification, each labeled — our method, including where it runs out.
The certified record
| Specification | Figure | Source |
|---|---|---|
| Smoke CADR | 577 CFM | ENERGY STAR |
| Dust CADR | 586 CFM | ENERGY STAR |
| Pollen CADR | 450 CFM | ENERGY STAR |
| PM2.5 CADR | 581 CFM | ENERGY STAR |
| Certified room size | 894 sq ft | ENERGY STAR, at 4.8 ACH |
| Two-thirds-rule room | 865 sq ft | Our arithmetic on the CADR |
| Annual energy use | 335 kWh | ENERGY STAR |
| Electricity per year | $61 | Our arithmetic at a named rate |
| Air per watt | 10.2 CFM/W | ENERGY STAR |
| Measured ozone | 0.00 ppb | ENERGY STAR |
| Technology | Fan and Filter | ENERGY STAR |
| Filter classification | HEPA-Type | ENERGY STAR |
| Power draw | 65 W | Coway |
| Noise | 23-46 dB(A) | Coway |
| Filter set | Max2 (activated carbon + HEPA), 1 year | Coway |
| Pre-filter | Washable, two XL sets | Coway |
| Replacement filter price | Not published in our sources | — |
| Sensors | PM1, PM2.5, PM10, with a filter change indicator | Coway |
| Size and weight | 18.9 x 36.6 x 24.3 in, 51 lb | Coway |
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.
Big and efficient, which is not the usual combination
Large machines are normally the thirsty ones: more air costs more watts, and the efficiency figures on this site generally fall as coverage rises. The ProX breaks that pattern, and it is the single most interesting thing about it.
At 10.2 CFM per watt it posts the highest Integrated Energy Factor we have recorded — ahead of the Blueair 211i Max at 9.0, which is the efficiency benchmark at a much smaller size. In practice it certifies 894 square feet on 335 kWh a year, which is less electricity than the LEVOIT Core 600S uses to cover 606 square feet (387 kWh) and less than the Coway Airmega 450 uses for 687 (389 kWh).
That is $61 a year against $71 and $71 — the largest machine on the site is also the cheapest of the large machines to run. Over the years a machine like this stays plugged in, that inverts the usual argument for buying small.
The quietest top speed of any large machine here
Coway publishes 23-46 dB(A). The number that matters is the top of that range: 46 dB(A), against 51 for the Alen BreatheSmart 75i, 52 for the Airmega 400, 55 for the Core 600S and 57.7 for the Airmega 450. Every one of those is a smaller machine.
The reason is straightforward physics rather than acoustic engineering: a large fan moving a given volume of air spins slower than a small one doing the same job. It is the practical case for oversizing a machine slightly — you run it at a middle setting where it is inaudible instead of running a smaller one flat out — how to read a dB range covers why the bottom of the range matters more in a bedroom and the top matters more in a room people talk in.
The column where it underperforms
Every certified machine posts three CADR figures, and pollen is almost always the highest of the three because pollen is the largest of the test particles. The ProX is one of only two machines we cover where that is not true: its pollen figure of 450 sits below its smoke figure of 577 and its dust figure of 586.
Be careful how much weight that carries. In absolute terms 450 CFM matches the highest pollen figures on this site — the Blueair 211i Max and the Airmega 450 post the same number. What it means is that the ProX’s advantage over those machines, which is large on smoke and dust, disappears entirely on pollen. If seasonal allergy is the specific reason you are buying, you are paying a premium for capacity that does not show up in the column you care about — the roundup that ranks on the pollen column explains why that column deserves its own ranking.
What else it gets right
A measured zero, with nothing bolted on. ENERGY STAR records fan-and-filter and 0.00 ppb; Coway’s specification lists no ionizing stage. At this size that is not a given — the other machines covering 600-plus square feet include two that measure 2 ppb with an ion classification the registers disagree about.
Washable pre-filters, in quantity. Coway ships two XL washable pre-filter sets and describes the main cartridge as activated carbon plus HEPA on a one-year schedule. In a house with animals the pre-filter is what protects the expensive part — the machines that document one remain a short list.
Sensors that report something specific. PM1, PM2.5 and PM10 readings plus a filter change indicator. This site does not rank on features, but a PM1 readout is more informative than the colored dot most machines offer, and the filter indicator is useful precisely because Coway publishes an interval for the cartridge.
Where it is beaten, and what is missing
No filter price we could source. Coway publishes the interval — one year — but no replacement price for the ProX Max2 set that we could find, so its annual filter cost cannot be computed. That is a real gap on a machine in this bracket, and it is the same gap as on the Airmega 450. Coway does publish both figures for the Airmega 400, which makes the omission here more conspicuous than it would be from another brand — what each manufacturer publishes about filter cost.
One register, not two. ENERGY STAR certifies it; AHAM does not list it, because AHAM’s directory does not carry Coway at all. That is one independent source rather than two. It is not a red flag — ENERGY STAR certification requires testing to the same ANSI/AHAM AC-1 standard through an EPA-recognized body — but the LEVOIT machines a bracket below now appear in both.
A filter the register classifies HEPA-Type, not HEPA, despite Coway describing the Max2 as a HEPA filter. The certified CADR already reflects what the filter removes, so this matters less than the label suggests, but the Honeywells at a fraction of the price are recorded HEPA — what the classifications do and do not promise.
It is a piece of furniture. 36.6 inches tall, 24.3 deep and 51 lb. That is roughly double the weight of the Airmega 450 and nearly four times the LEVOIT Core 600S. It will not be moved between rooms, so buy it for the room it is going to live in.
Coway’s own CADR is lower than the certified one. Coway publishes 568 smoke CADR for this machine; ENERGY STAR certifies 577. The gap is small, and it is in the same direction as the Airmega 400’s — this manufacturer understates its own machines, which is the opposite of the usual problem in this category.
The room it actually fits
| Room | ACH | Verdict |
|---|---|---|
| 500 sq ft | 8.7 ACH | Far more machine than the room needs |
| 721 sq ft | 6.0 ACH | Our 6 ACH pet-room target, exactly |
| 865 sq ft | 5.0 ACH | AHAM's two-thirds rule, exactly |
| 894 sq ft | 4.8 ACH | The register's own figure |
| 1,000 sq ft | 4.3 ACH | Short — nothing certified reaches it |
The bottom row is the honest ceiling of this whole category. At 1,000 square feet even this machine falls short of the rule, which is why our 1,000 square-foot page recommends two machines in two zones rather than one flagship.
Who should buy it
Buy it for a genuinely open floor between about 664 and 865 square feet — a loft, a great room, a converted open plan — where you want certified coverage, a measured zero and a machine quiet enough to leave running while people are in the room.
Buy something else if the space is smaller, which for most households it is: the Airmega 450 covers 687 certified square feet and the Core 600S 606, both for materially less money. And if pollen is the specific problem, the premium here buys you nothing over machines costing far less.
Quick picks
The ProX against the two machines a buyer at this size should actually weigh it against.
| # | Product | Best for | Certified CADR | Price |
|---|---|---|---|---|
| 1 |  The unit reviewed Coway Airmega ProX 577 certified CFM across 894 sq ft at 10.2 CFM per watt, 0.00 ppb measured. | The largest room one machine can certifiably cover | 577CFM smoke ENERGY STAR verified | |
| 2 |  If the room is under 664 sq ft Coway Airmega 450 443 certified CFM across 687 sq ft with the same zero and no ion stage. | Open-plan floors up to about 665 sq ft | 443CFM smoke ENERGY STAR verified | |
| 3 |  Cheapest to run at large size 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 |
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The alternatives worth weighing
Coway Airmega 450
Coway · model Airmega 450 (AP-2524B)
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687 certified square feet with zero measured ozone and a vacuumable pre-filter. The step between the Airmega 400 and the ProX, and the cheapest certified way past 600 square feet.
443 smoke / 445 dust / 450 pollen CFM · 444 PM2.5
- Certified room size
- 687 sq ft
- Advertised coverage
- 3,285 sq ft in 60 minutes
- Energy / year
- 389 kWh
- Electricity / year
- $71
- Air per watt
- 6.7 CFM/W
- Power draw
- 72 W
- Noise
- 23.6-57.7 dB(A)
- Measured ozone
- 0 ppb
- Filter class
- HEPA-Type
- AHAM rule, 650 sq ft
- Clears it (434 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.
443 certified smoke CADR across 687 certified square feet with the same 0.00 ppb, the same absence of an ion stage and a vacuumable pre-filter — for a materially smaller outlay. The full record on it.
The honest con: $71 a year is more electricity than the ProX uses for more room, its published range tops out at 57.7 dB(A) — the loudest we print — and Coway publishes no filter price for it either.
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 9.0 CFM per watt for $47 a year — the lowest electricity bill of any machine covering more than 600 square feet. The full record on it.
The honest con: ENERGY STAR measures 2 ppb rather than zero, AHAM classifies the Max range as carrying an ion generator with no documented way to switch it off, and Blueair publishes neither a noise figure nor a filter schedule.
Common questions
Is the Coway Airmega ProX worth it?
What size room does the Airmega ProX cover?
Can the Airmega ProX cover a whole house?
Is the Airmega ProX good for pollen?
Does the Airmega ProX produce ozone?
Sources
- ENERGY STAR certified room air cleaners database
- AHAM — air filtration standards and the two-thirds rule
- Coway Airmega ProX specification
- EPA — Guide to Air Cleaners in the Home
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
- Room sizeThe Best Air Purifiers for 1,000 Square FeetNo certified single unit covers 1,000 sq ft. The Coway Airmega ProX reaches about 865; past that the answer is two machines in two zones.
- Room sizeThe Best Air Purifiers for Large RoomsCertified for 500+ square feet, ranked on real coverage and what each costs to run.
- Room sizeCoway Airmega 450 Review687 certified square feet with 0.00 ppb ozone, a vacuumable pre-filter and three filter options — against the loudest published top speed we print and no filter price.