For most large rooms, the Blueair Blue Pure 211i Max is now the better buy than the Coway Airmega 400: more airflow, an app, lower power use and a lower price, with a three-year cost that ends up about level. The Coway's case is narrower but real. It filters with dual True HEPA and no ionizer, and it needs a new filter set only once a year. This is a research-based comparison built from Blueair's and Coway's published specs, not a hands-on test.
Quick answer
Choose the Blueair if you want the most clean air per dollar and per watt, plus app control. Choose the Coway if an always-on ionizing stage is a dealbreaker for you.
| Attribute | Blueair Blue Pure 211i Max | Coway Airmega 400 |
|---|---|---|
| CADR (smoke / dust / pollen) | 435 / 452 / 450 | 328 / 328 / 400 |
| Room size (CADR × 1.55) | ~674 sq ft | ~508 sq ft |
| Filtration | HEPASilent (electrostatic + mechanical) + carbon layer | Dual True HEPA + dual activated carbon |
| Ionizer | Yes, always on | None |
| Filter cost per year | ~$93–$140 ($69.99 every 6–9 months) | ~$129 (Max2 set, up to 12 months) |
| Rated noise | 23–53 dB | 22–52 dBA |
| Max power | 46 W | 66 W |
| Smart features | Auto + PM1/PM2.5/PM10 sensor + app | Auto + sensor, no app |
| Typical price | $230–$350 ($349.99 list) | $400–$450 |
Where the Blueair wins
The Blueair Blue Pure 211i Max wins on airflow. Its 435 CFM smoke CADR is about a third higher than the Coway's 328, which is the difference between roughly 674 and 508 sq ft at the site's sizing rule. In a 500 sq ft open living area with 8-foot ceilings, that's about 6.5 air changes an hour from the Blueair at full speed against 4.9 from the Coway. More headroom means the Blueair can clean the same room on a lower, quieter setting.
It also has the smarter feature set. The 211i Max has its own particle sensor, an auto mode, night mode, and an app with schedules, filter tracking and Alexa or Google Assistant control. The base Airmega 400 has a sensor and auto mode too, but nothing for your phone. And the Blueair does all this on a 46 W maximum, 20 W less than the Coway, while typically costing $50 to $200 less to buy.
Where the Coway wins
The Coway Airmega 400 wins on filtration type. It pulls air through two True HEPA filters, each with its own activated-carbon layer, and there's no ionizer anywhere in the airflow. The Blueair's HEPASilent design depends on an electrostatic charging stage that runs whenever the fan does. It is CARB certified, so ozone output is under California's limit, but if you want nothing ionizing in the house, the Coway is the one of these two that qualifies.
The Coway's filter routine is also simpler. One $129 Max2 set lasts up to 12 months, so it's one swap a year. The Blueair's filter needs changing every six to nine months. Its pollen CADR of 400 CFM is also close to the Blueair's 450, so for a spring-allergy room the airflow gap is smaller than the smoke numbers suggest.
What three years actually costs
Filter running cost is usually the Blueair's weak point, but against the Airmega 400 it isn't. Here's the three-year math, assuming the first filter ships in the box:
| Blueair 211i Max | Coway Airmega 400 | |
|---|---|---|
| Purchase | $230–$350 | $400–$450 |
| Filters to buy in years 1–3 | $210–$350 (3 to 5 at $69.99) | $258 (2 sets at $129) |
| Purchase + filters | ~$440–$700 | ~$658–$708 |
| Electricity ceiling (max speed 24/7 at $0.17/kWh) | ~$206 | ~$295 |
The Blueair's range is wide because it depends on two things: the price you pay (it is often discounted toward $230) and whether you change the filter at nine months or six. At list price with six-month changes it costs about the same as the Coway over three years. On sale with nine-month changes it is more than $200 cheaper. Neither maker publishes per-speed wattage, so the electricity row is a worst case; real use on auto will be a fraction of it, and the lower-wattage Blueair keeps its edge either way. The filter cost calculator lets you plug in your own prices.
How to choose
Buy the Blueair Blue Pure 211i Max if you're cleaning an open living area of 500 to 700 sq ft, want app control, or simply want the most airflow for the money. Registering it within 60 days extends Blueair's warranty from one year to three.
Buy the Coway Airmega 400 if you want True HEPA with no ionizer and a once-a-year filter change, and you're happy to pay roughly $50 to $200 more up front for it. If neither fits, say you want no ionizer and an app in the same machine, the Levoit Core 600S covers about 606 sq ft with both. Our best air purifiers for large rooms roundup puts all three in context.
Frequently asked questions
Is Blueair or Coway better for a large room?
On paper the Blueair Blue Pure 211i Max. Its 435 CFM smoke CADR covers about 674 sq ft at the site's 4.8 air-changes-an-hour standard, against about 508 sq ft for the Coway Airmega 400's 328 CFM. The Coway closes some of the gap on pollen (400 CFM), but for smoke and dust the Blueair has roughly a third more airflow.
Do the Blueair 211i Max and Coway Airmega 400 both have auto mode?
Yes. Both have an air-quality sensor and an auto mode that raises and lowers the fan for you. The 211i Max reads PM1, PM2.5 and PM10 and adds a Wi-Fi app with schedules and Alexa or Google Assistant control. The base Airmega 400 has no app; Coway sells Wi-Fi as a separate model, the Airmega 400S, at a much higher list price.
Which has cheaper filters, Blueair or Coway?
They land close. The Coway's Max2 set is $129 and lasts up to a year. The Blueair's $69.99 filter lasts six to nine months, which works out to about $93 to $140 a year. Change the Blueair filter at nine months and it is the cheaper of the two to feed; change it every six months and it costs slightly more.
Do the Blueair or Coway use ionizers?
The Blueair does. Its HEPASilent system charges particles with an ionizing stage before the filter, and there is no way to switch that stage off. Blueair's US models are CARB certified under the 50 ppb ozone limit. The Coway Airmega 400 uses dual True HEPA and carbon filters with no ionizer, which is its clearest advantage for anyone who wants purely mechanical filtration.
Is the Coway Airmega 400 worth more than the Blueair 211i Max?
For most buyers, no. The Airmega 400 typically sells for $400 to $450, against $230 to $350 for the 211i Max, and the Blueair has more airflow, an app and a lower power draw. Pay the Coway premium if you specifically want True HEPA with no ionizer and a once-a-year filter change.
