Coway Airmega 400 vs ProX

Choose the Coway Airmega 400 for a room around 500 square feet with an 8-foot ceiling, using its published full-speed capacity as the sizing limit. Choose the ProX when the room needs more particle-cleaning airflow: the EPA's sizing table calls for 390 CFM at 600 square feet, above the 400's manufacturer smoke CADR of 328 CFM and within ProX's 568 CFM. The larger model earns its floor space through capacity; check the room volume and usable fan setting before buying. (EPA sizing guidance, 400 specifications, ProX specifications)

Quick picks

• Airmega 400 — choose it when capacity is sufficient and floor space matters. Smaller cabinet, dedicated light control and a local shutdown timer.
• Airmega ProX — choose it for the larger connected room. Higher smoke and dust CADR, numerical particle readings and locking wheels, with a substantially larger cabinet.

Comparison table: US 400 non-S versus ProX

These are Coway's current US product-page specifications. Dimensions are width × height × depth; coverage figures retain their stated air-change basis.

Sources: 400, ProX, their manual directory, 400 filter set, ProX filter set, and the EPA's ProX connection record.

• Airmega 400328CFM
• Airmega ProX568CFM

Source: Coway's US product specifications, linked above; full-speed sizing does not describe Silent or Sleep mode.

Size the room on the same air-change basis

Don't size either machine from its largest coverage headline. Those headlines describe one air change per hour. AHAM's suggested-room-size method uses approximately 4.8 equivalent air changes per hour; filtered-air equivalents describe particle cleaning, rather than fresh outdoor air entering the room. (AHAM explanation)

Use that shared target with the published smoke CADR:

Required smoke CADR in CFM = floor area in square feet × ceiling height in feet × 4.8 ÷ 60.

This rearranges AHAM's room-volume relationship. Compare the result with 328 CFM for the 400 and 568 CFM for ProX. If it exceeds the relevant figure, choose more capacity or multiple appropriately placed units. Count the entire open area the purifier would serve; closed rooms need their own placement decision. (AHAM calculation, EPA room guidance)

For a calculation-free reference, the EPA estimates 325 CFM for 500 sq ft and 390 CFM for 600 sq ft, assuming an 8-foot ceiling. On Coway's figures, the 400 only just clears the first example; ProX clears both. Choose ProX if you want more margin near the smaller model's limit. Taller ceilings increase the volume, so use the formula instead of carrying those floor areas over unchanged. These are sizing estimates, not a promise of uniform results throughout a home.

1. 1

   Measure the connected space

   Include the whole open area and use its actual ceiling height.

2. 2

   Compare at a shared target

   Calculate demand at 4.8 equivalent air changes per hour and compare with the maker's smoke CADR.

3. 3

   Check the fan setting

   Published full-speed capacity cannot be assigned to a quieter mode without mode-specific CADR.

Airflow and smoke CADR are different. Coway's separate explainer uses 416 CFM airflow to describe the 400 covering 780 sq ft at four air changes per hour. That calculation does not use its product-page smoke CADR of 328 CFM. Keep the airflow-based coverage and particle-specific CADR separate when comparing the two machines. (Coway's two calculation methods)

Airmega 400: best when the smaller cabinet is enough

The 400 is easier to accommodate at 14.8 inches wide and deep. Its local controls include a 1-, 4- or 8-hour shutdown timer and a Light button. Smart mode adjusts fan speed to the particle sensor; in that mode, Eco can stop the fan after the sensor reports Good for more than 10 minutes. You can select speed or Sleep manually. (400 page, 400/400S manual)

For steady airflow, select a manual speed you can tolerate. The minimum 22 dB(A) specification doesn't establish that the machine delivers its full CADR at that sound level: the EPA notes that CADR is typically measured at highest speed and lower speeds filter less air.

Check the suffix: this pick is the US AP-2015F, non-S. The 400S adds Wi-Fi and app scheduling; Coway publishes the same CADRs and cabinet dimensions for both, and their Max2 filter set is shared. For the smaller step down, see our Airmega 250 versus 400 guide. (400S specifications)

See the non-S Airmega 400 at Coway.

Airmega ProX: best when the room needs more capacity

ProX's advantages extend beyond its higher CADR: its panel displays PM1.0, PM2.5 and PM10 numerically, and it has a control lock. The US manual identifies the AP-3522F family and describes locking wheels. At 51 lb, those wheels are useful for repositioning on a suitable floor; plan a permanent operating location before ordering. Its EPA directory record specifies no connected capability. (ProX manual, connection record)

Turbo is temporary: the manual says it uses airflow equivalent to manual Level 3, lasts 10 minutes, then returns to Auto. For continuous high speed, select manual Level 3. Silent reduces airflow; Auto can enter its sleep setting in darkness. To extinguish panel lights separately, hold the PM information button for more than 3 seconds. A dark panel therefore doesn't require selecting Silent.

The published 23–46 dB(A) range is Coway's claim. It doesn't establish that ProX will sound quieter than the 400 at an equal cleaning rate: neither cited page supplies comparable mode-by-mode CADR and sound measurements. For a choice led by nighttime noise, see quiet air purifiers for bedrooms.

See the Airmega ProX at Coway.

Cabinet clearance and filter access

Measure the full cabinet depth, especially ProX's 24.3 inches. Both manuals require a firm, flat, dry surface with adequate circulation, unblocked sides and an unblocked outlet. Leave practical access to remove the covers and filters on both sides; a cabinet-sized recess is a poor plan. The 20 cm antenna-separation text in the manuals is an electronics instruction, not a filter-intake clearance specification. (400 manual, ProX manual)

Two-sided filters: the complete replacement order

One genuine set supplies both sides. Compare the full-set order when checking ongoing cost. “Max2” alone doesn't identify which machine a filter fits; use the named compatibility above, and verify both filters are included in any alternative package.

There is a lifespan discrepancy: the purifier pages advertise 6–12 months, while the replacement-set pages specify 12 months. Use the latter as a nominal interval and follow the machine's replacement indicator. The washable pre-filters are separate; the manuals prohibit washing or reusing the Max2 filters.

Installation differs: unplug first and remove the shipping plastic from the inserted filters on both sides. The current 400 manual places the green face toward the product; the ProX manual places it toward the pre-filter frame, outside. Follow the manual matching your machine and its filter markings, refit both covers correctly, and reset the appropriate filter indicator after replacement. (400 instructions, ProX instructions)

Buying guide: audit the exact holiday listing

Use the model and contents, rather than the promotion label, to decide:

• Purifier or accessory: both maker pages offer a Genuine Filter selection alongside the machine. Confirm the order includes the purifier itself.
• Exact US version: check non-S 400 versus 400S, ProX's model family and the 120 V, 60 Hz supply.
• Complete filter order: confirm installed filters on both sides; count bundled spares as complete sets only when both sides are supplied.
• Condition and terms: read whether the offer is new, refurbished or open-box, who sells it, and its written warranty and return terms. Compare that exact package with the maker's model page.

This guide establishes model fit, not a current discount or retailer-stock claim. For smoke preparation and its different sizing demands, use our wildfire-smoke purifier guide.

How we choose

Recommendations come from official US specifications, model-matched manuals, EPA sizing guidance and AHAM's air-change method. This is a document-based comparison; no physical product evaluation informs the picks. The CADR table uses Coway's figures; model-specific AHAM directory entries were not independently retrieved.

Official documentation disagrees. The EPA product directory lists 376.0 CFM smoke CADR for AP-2015F and 577.0 CFM for ProX, whereas Coway's pages list 328 and 568 CFM. We cannot establish the reason for those differences, so the sizing recommendations retain the lower maker figures. Also, the 400 page still describes it as the largest-capacity option, conflicting with ProX's page; the model-specific specifications are more useful than that family marketing. (400 directory record, ProX directory record)

Sources were checked November 3, 2026. Our broader research approach is on How we choose.

Verdict

Buy the 400 when its capacity covers your room at a usable fan speed and its smaller cabinet is the better fit. Buy ProX when room volume justifies the higher smoke CADR and larger cabinet. For continuous high airflow on ProX, choose manual Level 3; for either machine, budget for the correctly named complete two-sided replacement set.