Coway Airmega 400 Review: Big-Room Purifier With a 5-Year Warranty

What the Airmega 400 is

The 400 is a square tower that pulls air in through both side panels, each with its own washable pre-filter and Max2 filter (a combined HEPA and activated carbon cartridge), and blows it out of the top. A particle sensor and a light sensor drive Smart Mode: the fan rises with pollution, Eco Mode turns it off after 30 minutes of clean air, and Sleep Mode lowers noise and power when the room has been dark and clean for three minutes, according to the Amazon listing. The 400S adds Wi-Fi and app control; Coway lists it at $749.

Coway Airmega 400 CADR and coverage

Coway's product page lists 328 cfm for smoke, 328 for dust and 400 for pollen, and coverage of 1,560 sq ft at two air changes an hour or 3,120 sq ft at one. A Coway blog post gives different figures (285 smoke, 358 dust, 450 pollen); we use the product page. We found no Coway model in the AHAM Verifide directory on November 3, 2026, so neither figure can be checked against AHAM's database.

Air changes per hour from Coway's 328 cfm smoke CADR, 8 ft ceilings.

Room	Floor area	Air changes an hour
Large main bedroom, 16 x 20 ft	320 sq ft	7.7
Living room, 20 x 25 ft	500 sq ft	4.9
Open plan, 25 x 30 ft	750 sq ft	3.3
Coway's 2 air change figure	1,560 sq ft	1.6 (at 8 ft; Coway's own math differs)

The last row shows why coverage claims need a second look: with 8 ft ceilings, 328 cfm gives 1.6 air changes in 1,560 sq ft, not 2. Coway's figure likely assumes a different ceiling height or CADR. For allergies or smoke, size the 400 for 500 sq ft or less. Our sizing calculator runs the sum for your room.

Filters and running cost

Each side takes a Max2 filter, and Coway sells the pair as a Max2 filter set for $129, rated for about a year; replacement pre-filters are $35. The carbon is part of the Max2 cartridge rather than a separate bed, so for heavy odors a machine with a dedicated carbon filter does more.

Three-year cost at Coway's list prices. Electricity assumes 12 hours a day at the full 66 W and 17.2 cents per kWh, EIA's 2025 US residential average. Our arithmetic, a worst case.

Item	Cost
Purifier (Coway list price)	$649
Max2 filter sets, 3 years	$387
Electricity, 3 years	up to $149
Total	about $1,185

Noise, power and ozone

Coway lists 22 to 52 dB(A) and 66 W, which is quiet and efficient for a machine of this size. The 400's filtration is mechanical, with no ionizer listed, and the Airmega 400 (AP-2015F) and 400S (AP-2015E) appear on the California Air Resources Board's certified list as mechanical air cleaners.

Airmega 400 vs the alternatives

CADR from AHAM's directory except where marked.

Model	Smoke CADR	Room size	Notes
Coway Airmega 400	328 cfm (Coway)	About 500 sq ft at 4.8 air changes (our arithmetic)	5-year warranty, $129 filters
Levoit Core 600S-P	391 to 394 cfm	606 to 611 sq ft	AHAM listed, app
Winix C909	337 cfm	522 sq ft	AHAM listed
Honeywell HPA300	300 cfm	465 sq ft	No sensor, lower price
Blueair Blue Pure 211i Max	435 cfm	674 sq ft	AHAM listed, very efficient

For a certified big-room machine, the Blueair Blue Pure 211i Max moves more air for less power. For the lowest purchase price at this size, the Honeywell HPA300 covers 465 sq ft.

Who should buy the Coway Airmega 400

• Buy it for an open plan room or large bedroom of 300 to 500 sq ft if you value a long warranty and a quiet low setting.
• Buy it if you want a hands-off machine; Smart, Eco and Sleep modes run on the sensors.
• Skip it if you want certified figures; AHAM-listed machines at this size cost less.
• Skip it if filter cost matters; $129 a year is high next to Coway's own $59.79 Mighty set.

More options are in our best purifiers for large rooms.