Honeywell HPA300
AHAM verified
- Really cleans
- 457 sq ft42 m² 42 m²457 sq ft
- Box says
- 465 sq ft43 m² about right
- New filter
- 3–12 months
Coway · Airmega 400S
Coway Airmega 400S
Not verified. A verified model that cleans at least as much: Winix 9800, 513 sq ft47 m².
Really cleansNot verified
499 sq ft46 m² 46 m²499 sq ft
At 4.8 air changes an hour with a 2.5 m ceiling
- Box says
- Purifies 3,120 ft² in 60 minsPurifies 3,120 ft² in 60 mins (290 m²) 6.2× overstated
- New filter
- Every 6–12 months
See it on Amazon: Coway Airmega 400SPaid link
A big two-filter Coway tower with app control. Coway's CADR isn't independently verified, so we don't pick it.
Verdict
Who it's for
A popular large-room purifier with a filter set on each side. At Coway's figure it would clean a living room with a dining area, but nobody has verified that. The Winix 9800 is a verified alternative of similar size.
Good
- Particle sensor and auto mode
- App control
- No ionizer
Trade-offs
- CADR not independently verified
- Takes two filter sets
- Large and heavy
Spec facts
Coway Airmega 400S · Airmega 400S
- Really cleans
- 499 sq ft · 46 m²46 m² · 499 sq ftat 4.8 air changes an hour, 2.5 m ceiling
- Smoke CADR
- 328 CFM · 557 m³/hMaker’s figure, not independently verified
- Maker’s claim: Coway · checked 1 Nov 2026
- Box claim
- Purifies 3,120 ft² in 60 minsPurifies 3,120 ft² in 60 mins (290 m²)6.2× overstated
- Maker’s claim: Coway · checked 1 Nov 2026
- Filter
- Coway Max2 filter set (two per unit)Washable pre-filter + activated carbon and HEPA. Replace every 6–12 months
- Maker’s claim: Coway · checked 1 Nov 2026
Maker’s claim: the manufacturer’s own figure, not independently checked. Where figures come from
Running it
Filter and upkeep
- Replacement filter
- Coway Max2 filter set (two per unit)
- Type
- Washable pre-filter + activated carbon and HEPA
- Replace every
- 6–12 months
- Power at top speed
- 66 W
A new filter every 6–12 months means 1–2 filters a year. At top speed it draws 66 W: 1.6 kWh if it ran flat out all day. Slower settings use less.
We have no Amazon link for this filter: the maker's page in the sources sells or lists it.
Source: Maker’s claim, Coway, checked 1 Nov 2026
The box vs the maths
The box says 3,120 sq ft290 m². It really cleans 499 sq ft46 m².
To clean 3,120 sq ft290 m² it would only change the air in the room 0.8 times an hour. We size every purifier at 4.8 air changes an hour, the level AHAM's room-size guideline works out to.
Coway's figure is the room it can change the air of once an hour, and the wording says as much. That's a real number, but at one air change an hour smoke and pollen come back in nearly as fast as the purifier removes them. The CADR behind both numbers is Coway's own; AHAM hasn't certified it.
557 m³/h smoke CADR ÷ (4.8 × 2.5 m ceiling) = 46.4 m² = 499.9 sq ft46.4 m²
Use the calculator for your exact room and ceiling, or read how we pick.
Drawn to scale: the box says “Purifies 3,120 ft² in 60 mins”, the purifier really cleans 499 sq ft, 6.2 times less.Drawn to scale: the box says “Purifies 3,120 ft² in 60 mins”, the purifier really cleans 46 m², 6.2 times less.
Room sizes
Which rooms it fits
It suits 269 sq ft25 m², 322 sq ft30 m² and 376 sq ft35 m² rooms best: there it has 31–84% more air than the room needs, so it needn't run flat out. At 430 sq ft40 m² it only just keeps up (15% to spare), so it would run near its top speed, usually its loudest (why we don’t list noise). In rooms of 215 sq ft20 m² or less it's more than twice the size needed; a smaller model does the job.
Under a 2.7 m ceiling it covers 462 sq ft, under 3 m 416 sq ftUnder a 2.7 m ceiling it covers 42 m², under 3 m 38 m², so with a 3 m ceiling it no longer covers 430 sq ft40 m² (why).
For a 538 sq ft room or bigger it's too small, although the box claims 3,120 sq ft: the For a 50 m² room or bigger it's too small, although the box claims 290 m²: the 538 sq ft50 m² page lists models that cover it. In an open-plan space, add up every area without a door between (how).
All of this rests on Coway's own CADR figure. AHAM hasn't certified it, so we never make it a pick; a certified model is the safer buy at the same size.
Alternatives
The Coway Airmega 400S or one of these?
The certified models closest in size, and what is different about each, from the same kinds of source.
Cleans 457 sq ft, 42 sq ft lessCleans 42 m², 4 m² less, on a certified CADR. It has no air quality sensor. It needs filters more often (every 3–12 months).
Winix 9800
AHAM verified
- Really cleans
- 513 sq ft47 m² 47 m²513 sq ft
- Box says
- 2,506 sq ft233 m² 4.9× overstated
- New filter
- 3–12 months
Cleans 513 sq ft, 14 sq ft moreCleans 47 m², 1 m² more, on a certified CADR. It has an ionizer you can switch off. It needs filters more often (every 3–12 months). 2.7 kg lighter.
Levoit EverestAir-P
AHAM verified
- Really cleans
- 539 sq ft50 m² 50 m²539 sq ft
- Box says
- 2,635 sq ft245 m² 4.9× overstated
- New filter
- 12–15 months
Cleans 539 sq ft, 40 sq ft moreCleans 50 m², 4 m² more, on a certified CADR. It goes longer between filters (every 12–15 months). 1.8 kg lighter.
Sources
Where these numbers come from
- Maker’s claim Coway Airmega 400S product page and specifications · Coway
- Maker’s manual Coway Airmega 300 / 400(S) user manual (PDF) · Coway
We don't test purifiers ourselves: every figure on this page is copied from these sources and was last checked on 1 Nov 2026. Spotted one that's wrong or out of date? Tell us and we'll fix it and change the date.