Coway Airmega 400S Review: Whatever you need in this Smart enabled air purifier!
Airmega 400S Specification
Product | Airmega 400S |
Dimension | 14.8 x 22.8 x 14.8 in (37.6 x 57.9 x 37.6 cm) |
Weight | 24.7 lb (11.2 kg) |
Fanspeed | 3 |
Coverage (up to) | 1560 sq. ft. (145 m2) |
Airflow speed | |
Dust free (CADR) | 350 cfm (595 m3/h) |
Pollen free (CADR) | 350 cfm (595 m3/h) |
Smoke free (CADR) | 350 cfm (595 m3/h) |
Filtration | 4-stage |
Pre-Filter - Lifespan - Replacement cost ($) | Pre-filter (2 pack) Permanent +- 25 |
HEPA filter - Lifespan - Replacement cost ($) | Max2 (Green True HEPA filter) 1 year |
Carbon filter - Lifespan - Replacement cost ($) | Max2 (Activated carbon filter) 1 year |
Ionizer/ Technologies | |
UV-light/ PCO | - |
Other filter | - |
All-in-one filter - Lifespan - Replacement cost ($) | Max2 Filter 1 year +- 129.99 |
Optional/ Addon | - |
Noise level | 22 - 52 dB |
Power usage level | 6 - 66 W |
Timer/ Scheduler | 1, 2, 4, 8 hours (App), Scheduler |
Sensors | Pollution sensor, Light sensor |
Auto mode | |
Air qualityAQ indicator | |
Filter change indicator | |
More color options | |
Wi-Fi/ BTBluetooth | |
ENERGY STAR | |
Remote control | |
Child lock | |
Warranty | 5 years |
Email/ Phone support |
Key features
- Wi-Fi connectivity for AIRMEGA app integration
- Works with Amazon Alexa
- 4-stage filtration
- Permanent Pre-filter
- MAX2 filter (99.97% True HEPA filter + 99% Activated Carbon filter)
- 3 fanspeed (Low, Medium, High)
- Dual air suction via side air inlet
- Dedicated Pre-filter and HEPA filter indicator (Change, Wash)
- Smart mode - Auto, ECO and Sleep mode
- Real-time air quality monitor (Good, Moderate, Unhealthy, Very Unhealthy)
- Adjustable pollution sensor's sensitivity (sensitive, normal, less sensitive)
- Scheduler/ Timer via IoCare app (1, 2, 4, 8 hours)
- 5 years warranty
Pros
- 4-stage filtration with widest purifying coverage in its group.
- Dual pre-filter that cover and protect the HEPA filter from large particles like dust.
- Outstanding allergens and smoke filtration via MAX2 filter (Full-size HEPA + Carbon).
- Auto mode that accurately adjusts the fan speed based on room air quality.
- Light/ sleep mode that automatically tones down the noise and speed when the room is dark.
- Separate Pre-filter and MAX2 lifespan indicator that based on real-time usage.
- Timer + advanced scheduler for 7 days customizable on and off setting (via IoCare app).
- Highly legible and accurate real-time air quality monitor.
- Standard 5 years manufacturer warranty.
Cons
- All Airmega air purifiers are expensive. This is the most expensive version of its series.
- Filter replacement cost is high although Max2 set consists of both HEPA and Carbon filter.
- Slight learning curve on Wi-Fi connectivity especially for first time user.
- No Ionizer as an option.
- Timer is only accessible via Airmega app.
The starters
Simplicity meets modern architecture. Coway Airmega 400S manage to perfect the art of design with its seamless dual side air inlet. The 14.8 x 22.8 x 14.8 in size and 24.7 lb weight is considerably compact for its category if you discounted the four fixed legs. Build quality is top-notch that does not seem to be any signs of ozone off-gassing or air by-pass. Upfront, there is a LED ring AQ indicator with real-time (every minute) air pollution update. Up to four different colors will be shown on the air quality status. Starting from Good (Blue and green), Moderate (Green and yellow), Unhealthy (Yellow and pink) to Very Unhealthy (Pink and red). Finally, to lift or transport the air purifier around, simply hold on to both sides of the handles.

Controls are located at the top black panel that separates into two sections. On the left side, you will find a Wi-Fi button, Light button, Pre Wash button, and Max2 change button. Touching the Wi-Fi button connect the air purifier to a Wi-Fi network. The Wi-Fi LED indicator will start blinking when the pairing is in progress. Once a stable connection is established, the LED indicator will stay constant. The light button will turn on or off the air quality indicator light. Pre Wash button will shows the pre-filter cleaning cycle at 5 levels: 100%, 80%, 60%, 49%, 20%, and 0%. Once the button is lit, you will need to clean the pre-filter. To reset the Pre Wash filter Lifetime notifications, touch and hold the button for 2-3 seconds. The above steps apply to Max2 Change button as well. Instead of cleaning the filter, you will need to replace the Max2 filter. Light sensor function by detecting the intensity of ambient light. When the air purifier is in Smart mode and surrounding is in pitch black for 3 minutes, Sleep mode will activate.
Moving to the right side, you have the big main Power button that is self-explanatory. Touch the button once to turn on the air purifier, touch and hold the same button again for 2-3 seconds to turn it off. To manage the fan speed or purifying mode, either touch or swipe your finger upward or downward on the curve bar. One more secret function that most people didn’t know unless they read the manual (how many of you does that). you can adjust the sensor’s sensitivity by holding on the Light button +Smart bar. Continue by selecting one of the fan speed (speed 1 = sensitive, speed 2 = normal, speed 3 = less sensitive). Overall, all buttons are responsive, clearly labeled with dedicated indicator light.
Like 300S, the Wi-Fi enabled feature that allows you to control the air purifier at any place via IoCare app. Pairing is easy for both Apple and most Android phones so long you have strong Wi-Fi connectivity. We did encounter some issues with some lower end model (Huawei to be exact) that requires few retries. Upon successful connection, you can access features like timer, speed, Smart Mode, and scheduler. Highlights would be on the scheduler that allows you to program weekly activities. You can also access indoor/ outdoor air quality report and Real-time Air Monitoring.
Airmega 400S also works with Amazon Alexa where you could control specific functions. The standard list of voice command includes on/ off, switching mode, fan speed, timer, check filter life, and air quality.
Briefly go through other key specification again. A standard 4-stage filtration, 3 fan speed with Smart mode (Auto/ Sleep/ Eco). Wi-Fi enabled for Airmega’s IoCare app and Amazon Alexa support. Pre-filter/ MAX2 life-time indicator (actual filter real-time usage lifespan). Lastly, air quality indicator, 30 days money back guarantee and 5 years warranty.
Airflow, speed, and CADR
What’s inside count
Airmega 400S uses the same 4-stage filtration setup that is proven against the test of time. Essentially a dual pre-filter plus Max2 filter bundled (True HEPA and Activated Carbon). Each pre-filter would cover both sides of air inlet for incoming airborne contaminants. With large particles out of the way, Green True HEPA filter would focus on microbes allergens. Anything that is 0.3 microns or bigger with not be able to bypass the HEPA filter excluding gas particles. That job belongs to Activated Carbon filter that will absorb nearby smoke and odors. There is no optional Ionizer included in the filtration list; Not a big miss for some.Keep it down
At what cost
^ Replacement filters/ estimated cost
Airmega 400S VS the challengers

Airmega 400
Identical in every way except it's around $100 cheaper due to the lack of Wi-Fi + Alexa support. This is the air purifier to go for if you have no use of the remote access.
Airmega 300S
The smaller, cheaper, and Wi-Fi ready version that is indistinguishable at first glance. Airmega 300S has a weaker overall performance and lacks filter real-time usage indicator.
Coway AP-1512HH Mighty
Coway best-selling air purifier that is priced a lot less with decent airflow. Coway Mighty filtration performance wise is incomparable to Airmega 400S.