Coway Airmega 300 vs 350 vs 400 vs 400S: Which Purifier for an Open-Plan Floor or Whole Apartment

By Simone Ellery · Updated 2026-10-23T02:53:04.835Z · How we choose · How we make money

We may earn a commission if you buy through links on this page, at no extra cost to you. Our picks are based on the data shown, not on what pays us.

What changed: All four models are currently at their 90-day low, with prices flat over the period.

Airmega 300

$549.00 90-day range $549.00 – $549.00 trend: flat Lowest price in 90 days

Pros

• 285 CADR and a listed 2512 sq ft coverage rating suit an open-plan floor
• Runs as quiet as 22 dB and draws 57 W
• At $549.00 it sits $100.00 below the Airmega 400 and $200.00 below the 400S
• Price is at its 90-day low and has been flat

Cons

• 285 CADR is the lowest of the four listed purifiers
• Costs $210.00 more than the Airmega 350, which lists a higher 352 CADR
• 21.4 lb and 13.6 x 21.2 x 13.6 in make it heavier than the 17.2 lb Airmega 350

Who it's for: Someone purifying an open-plan floor or whole apartment on a budget who wants a quiet unit and will trade some CADR for a lower price than the 400 series.

Check price at cowaymega.com

Airmega 350

$339.00 90-day range $339.00 – $339.00 trend: flat Lowest price in 90 days

Pros

• 352 CADR is the highest in the series, above the Airmega 300's 285 and the 400/400S's 328
• 2640 sq ft coverage suits an open-plan floor or a whole apartment
• 21.5 dB is the quietest listed, and at 17.2 lb it's the lightest unit here
• At $339 it's the cheapest of the four, $210 below the Airmega 300 and $410 below the 400S

Cons

• 62 W draw is higher than the Airmega 300's 57 W
• Filter replacement is needed once a year

Who it's for: A shopper who wants the most airflow and coverage for the least money in this lineup, with the lowest noise and weight.

Check price at cowaymega.com

Airmega 400

$649.00 90-day range $649.00 – $649.00 trend: flat Lowest price in 90 days

Pros

• 3120 sq ft coverage, the largest in the series, suited to an open-plan floor
• CADR of 328 for smoke and particle removal
• 22 dB minimum noise and 1-year filter life
• Price held flat at its 90-day low of $649.00

Cons

• 24.7 lb and 14.8 x 22.8 x 14.8 in, the heaviest and bulkiest of the group
• Costs $100.00 more than the Airmega 300 and $310.00 more than the Airmega 350
• 66 W power draw, higher than the 300's 57 W and the 350's 62 W

Who it's for: Anyone needing maximum coverage for a large open-plan space or whole apartment during a smoke event who can accept the extra weight and cost.

Check price at cowaymega.com

Airmega 400S

$749.00 90-day range $749.00 – $749.00 trend: flat Lowest price in 90 days

Pros

• 3120 sq ft coverage suits an open-plan floor or whole apartment
• CADR of 328 for smoke-event filtration
• Runs at 22 dB, quiet enough for living spaces

Cons

• At $749.00 it is the priciest in the lineup, $100.00 more than the Airmega 400
• 1-year filter life means annual replacement

Who it's for: Buyers who want the largest coverage in this lineup and will pay $100.00 over the Airmega 400 for it.

Check price at cowaymega.com

How we chose

We compared the four models on coverage, CADR, size, weight and current price. All four are at their 90-day low. The Airmega 350 is the lowest-priced at $339.00, and the Airmega 400S is the highest at $749.00, $410.00 more than the 350. The Airmega 400 costs $310.00 more than the 350, and the Airmega 300 sits between them at $549.00, $210.00 more than the 350.

Coverage and CADR don't rise together across the lineup. The Airmega 400 and 400S both cover 3120 sq ft at 328 CADR. The Airmega 350 covers 2640 sq ft at 352 CADR, the highest CADR here, and the Airmega 300 covers 2512 sq ft at 285 CADR.

Size and weight differ too. The Airmega 350 measures 12 x 12 x 23 in and weighs 17.2 lb. The Airmega 300 measures 13.6 x 21.2 x 13.6 in and weighs 21.4 lb. The Airmega 400 and 400S share 14.8 x 22.8 x 14.8 in dimensions; the 400 weighs 24.7 lb. Noise ratings are 21.5 dB for the 350 and 22 dB for the 300 and 400.

Who should skip these

If you're shopping for a single small room, this family is more machine than you need. The smallest coverage here is the Airmega 300 at 2512 sq ft, and it's also the second-priciest at $549.00. The Airmega 350, at $339.00, is the lowest-priced unit in the lineup, but it still lists 2640 sq ft of coverage.

If your budget is under $300, none of these fit. The Airmega 350 is the cheapest at $339.00, and every other unit costs more: the Airmega 300 is $210.00 more than the 350, the Airmega 400 is $310.00 more, and the Airmega 400S is $410.00 more.

The larger units also take up more floor space. The Airmega 400 and 400S each measure 14.8 x 22.8 x 14.8 in and weigh 24.7 lb for the 400, so they suit an open-plan floor rather than a bedroom corner. If you want a compact unit for one room or a spend below $300, look outside this family.

How to choose the right one

Start with floor area. The Airmega 350 covers 2640 sq ft, the 300 covers 2512 sq ft, and the 400 and 400S each cover 3120 sq ft. If you are treating one open-plan floor or a whole apartment, the 3120 sq ft figure is the one to match against your space; the 350 and 300 sit a step below it.

Then weigh CADR against footprint. The 350 has the highest CADR here at 352, in a 12 x 12 x 23 in cabinet weighing 17.2 lb. The 400 and 400S are rated at 328 CADR in a larger 14.8 x 22.8 x 14.8 in body, 24.7 lb for the 400. The 300 is rated at 285 CADR at 13.6 x 21.2 x 13.6 in and 21.4 lb. All four list a 1 Year filter life; noise is 22 dB on the 300, 400 and 400S and 21.5 dB on the 350.

Price is the last filter. The lineup runs from $339 to $749. The 350 is $210.00 less than the 300, the 400 is $100.00 more than the 300 and $310.00 more than the 350, and the 400S is $100.00 more than the 400 and $410.00 more than the 350.

Questions readers ask

By Simone Ellery · Published 2026-09-22 · Updated 2026-10-23