Where they actually differ
The most decisive specs, ranked by how much they matter — before the full spec table.
| Spec | Blueair - Blue Pure 311i+ Max | Coway - Airmega 400 |
|---|---|---|
| Coverage | 35 m² | 60 m² |
| CADR | 500 m³/h | 705 m³/h |
| Min noise | 23 dB | 22 dB |
Between the Blue Pure 311i+ Max and Airmega 400, the Blue Pure 311i+ Max comes out ahead in several specs, while the Airmega 400 wins on coverage / cadr. Overall, the Blue Pure 311i+ Max scores 77.4 and the Airmega 400 scores 85.4 on our Mars Score.
Which should you buy?
The Airmega 400 is the clear pick on raw spec strength, leading by 8.0 points on the Mars Score. The margin is wide enough that the underdog only makes sense if its individual strengths line up with what you specifically need.
The Blue Pure 311i+ Max does not pull ahead on any single popular-comparison spec — its strengths sit in the spec-table groups rather than the headline advantages.
Pick the Airmega 400 if you care most about coverage / cadr. Its strongest claims are coverage, cadr, min noise. The single most decisive one: Coverage — 71.43% more. 60 m² vs 35 m².
Both ship with comparable true hepa h13+, activated carbon, so those specs do not separate the two — focus on the differences below.
Bottom line: the Airmega 400 is the safer default. The other model is the right choice only when its specific advantages line up with your priorities.
Which should you buy: Blueair - Blue Pure 311i+ Max or Coway - Airmega 400?
Coway - Airmega 400 leads the current Mars Score by 8.0 points.The more useful decision is the trade-off behind that result: compare cadr, coverage, min noise against the way you will actually use the product.
Choose Blueair - Blue Pure 311i+ Max if…
Blueair - Blue Pure 311i+ Max does not lead a decisive measured field here, so choose it for price, ecosystem, design, or availability when those matter more to you.
Choose Coway - Airmega 400 if…
Coway - Airmega 400 has the measurable edge on coverage m2, cadr m3h, noise db min.
This is a structured comparison of the published catalog values. It is not a claim of identical real-world performance across every workload; use the linked spec drill-downs and methodology page to inspect the inputs.
Why Blueair - Blue Pure 311i+ Max wins
- No decisive advantages.
Why Coway - Airmega 400 wins
- ▲Coverage — 71.43% more. 60 m² vs 35 m².
- ▲CADR — 41.00% more. 705 m³/h vs 500 m³/h.
- ▲Min noise — 1.00 dB less. 22 vs 23.
Spec comparison
Performance
| Spec | Blueair - Blue Pure 311i+ Max | Coway - Airmega 400 |
|---|---|---|
| CADR | 500 m³/h | 705 m³/hlead |
| Coverage | 35 m² | 60 m²lead |
| True HEPA H13+ | true | true |
| Activated carbon | true | true |
Smart & Noise
| Spec | Blueair - Blue Pure 311i+ Max | Coway - Airmega 400 |
|---|---|---|
| Min noise | 23 dB | 22 dBlead |
| Air quality sensor | true | true |
| Smart app | true | true |