Coway Airmega 400S review

The Coway Airmega 400S is the connected counterpart to the local-control Airmega 400: a large, two-sided purifier with app control, scheduling and voice-assistant setup. Its case is not a different room-size class or a numeric display on the appliance. The 400S fits when a large room needs the same conservative airflow comparison as the 400, but you want the option to check or schedule it from a phone. If you will never use connected controls, the simpler 400 is the closer match.

Read the room figures at the cleaning rate you mean

Coway lists 3,120 square feet at one air change per hour and 1,560 square feet at two. That 3,120-square-foot headline describes a slow one-change rate, not repeated cleaning. The shared U.S. 400S/400 manual gives 1,560 square feet at two changes and 780 square feet at four, assuming an eight-foot ceiling. For this guide’s common 4.8-ACH comparison, 1,560 × 2 ÷ 4.8 equals 650 square feet. This 650-square-foot figure is a rate-scaled comparison, not a 4.8-ACH claim Coway directly prints. It clears the 606-square-foot large-room step used in the finder, but with little margin for an open plan, a high ceiling, doors between rooms or blocked airflow. A higher fan setting may also sound different from a quiet or automatic mode.

The product page publishes separate CADRs of 328 CFM for smoke, 328 for dust and 400 for pollen. Those pollutant-specific ratings are not a generic, pollutant-independent CFM number; the comparison fields keep generic CADR unknown rather than selecting one value to satisfy a hard minimum. They are Coway figures, not our own measurements.

Choose 400S for the connected routine, not a new filter layout

The exact user manual identifies the 400S as AP-2015E, separate from non-Wi-Fi 400/AP-2015F. White and Graphite are finish offers within this 400S family. The unit retains direct power and mode controls, sensor-based Auto, Sleep, Eco and three manually selected airflow levels. The app is an additional control path, not a requirement to use those local modes. Coway lists remote app operation, real-time air-quality monitoring, scheduling and timer choices of one, two, four or eight hours through its IoCare+ app. The manual also has Wi-Fi setup and Google Home/Amazon Alexa integration sections for the 400S and 300S models.

That connected setup brings dependencies. The product page says a router must support both 2.4 and 5 GHz, or 2.4 GHz alone; a 5-GHz-only setup will not work. A lost connection or an app you do not want to use should not make basic local operation essential, but connected commands and scheduling depend on the network and service. Coway’s page shows a colored air-quality signal and the manual’s panel uses color categories. It does not establish a numeric PM2.5 value on the purifier, and the app’s phrase “real-time air quality monitoring” does not by itself prove an in-app numerical particle reading. If exact PM values are your must-have, compare a model whose specific page and manual document them rather than interpreting the 400S’s color feedback as a number.

Auto adjusts among three fan levels according to the sensed air-quality category. In Eco, the manual says the fan can stop when the indicated air quality remains good, then restart when pollution is detected; Sleep behavior also responds to darkness and good air quality. These are useful automatic routines, but they are not a promise of sustained top-speed room coverage. Select the highest manual speed when the higher airflow basis matters, and decide whether the resulting noise fits where people sleep or work.

Budget for two filter sides and keep both clear

The 400S arrives with two washable pre-filters and a pair of Max2 filters, one set on either side. The Max2 media combines HEPA and activated carbon. Remove shipping plastic before the first run; do not wash or reuse the Max2 filters. Coway recommends vacuuming the pre-filters, gently washing them if needed and shade-drying them fully before reinstalling. The manual shows separate pre-filter and Max2 indicators and reset steps. The product copy describes the Max2 interval as six to twelve months in one place and one year in its specifications, while the manual relies on use indicators rather than a fixed calendar schedule. Treat filter life as a condition-based estimate and replace the matched pair together. The particle sensor also needs periodic cleaning; a light sensor or particle sensor is not a gas monitor.

The body is 14.8 inches wide and deep, 22.8 inches high and 24.7 pounds. Those are shell measurements, not the working opening: the manual calls for keeping both side intakes and the top outlet unobstructed and does not give a numeric wall clearance in the inspected English instructions. At a published 66 watts and 22–52 dB(A), it is a substantial appliance to run in a quiet bedroom. The page’s filtration and capture language is Coway’s own claim, not an independent test result.

Choose the 400S if you want app scheduling or remote access, accept the Wi-Fi requirements, and have room for a large two-sided purifier. If the app is irrelevant, compare the Airmega 400: it has the same stated room basis, filter arrangement and footprint, but no Wi-Fi. If you need numeric particle readings on the appliance or easier rolling movement, the Airmega 450 has a different local display and wheels; compare its own room basis and filter routine before choosing it. Neither the 400S nor its included general-carbon Max2 filters are a substitute for a documented TVOC sensor or an included specialty pet filter.