Blueair Blue Pure 211i Max
#6 in Large roomsFull review
A large-room purifier with very high certified CADR and low running costs, for open-plan living areas.
Amazon $349$349
The Blueair Blue Pure 211i Max is the better air purifier overall, rated 3.7 to 2.7. The Blueair Blue Pure 211i Max leads on value, filter cost and efficiency. The Blueair Blue Pure 211i Max costs $330 less ($349 vs $679).
AirDoctor AD4000
#15 in Large roomsFull review
A large-room purifier with strong certified CADR and odor filtration, but high filter costs.
Amazon $679$679
Prices were last checked October 22, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the Blueair Blue Pure 211i Max for value ($0.80 per cfm of smoke CADR vs $1.84 per cfm of smoke CADR), filter cost ($139.98 a year in filters vs $239.90 a year in filters) and efficiency (9 cfm per watt vs 5.6 cfm per watt).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every large rooms air purifier; a clear win is highlighted. How we rank explains each one.
| Factor weight | Blueair Blue Pure 211i Max | AirDoctor AD4000 |
|---|---|---|
| Overall rating | 3.7/5 | 2.7/5 |
| Value 25% | 70 $0.80 per cfm of smoke CADR | 0 $1.84 per cfm of smoke CADR |
| Filter cost 20% | 68 $139.98 a year in filters | 22 $239.90 a year in filters |
| Quiet 20% | 47 53 dB at top speed (maker rating) | 50 noise at top speed not published (neutral score used) |
| Efficiency 15% | 88 9 cfm per watt | 45 5.6 cfm per watt |
| Auto mode 10% | 100 particle sensor and Wi-Fi app | 70 PM2.5 sensor, auto mode |
| Warranty 10% | 0 1-year warranty | 50 warranty not published (neutral score used) |
Specifications
| Blueair Blue Pure 211i Max | AirDoctor AD4000 | |
|---|---|---|
| Performance | ||
| Smoke CADR | 435 cfm | 370 cfm |
| Dust CADR | 453 cfm | 393 cfm |
| Pollen CADR | 450 cfm | 450 cfm |
| PM2.5 CADR | 444 cfm | 381 cfm |
| CADR certified by | AHAM Verifide | ENERGY STAR |
| Room size (AHAM) | 674 sq ft | 574 sq ft |
| Coverage (maker) | 3,235 sq ft | 2,776 sq ft |
| Noise | 23 to 53 dB | - |
| Efficiency | ||
| Efficiency (IEF) | 9 cfm/W | 5.6 cfm/W |
| ENERGY STAR | Yes | Yes |
| Energy use | 256 kWh/year | 396.2 kWh/year |
| Filters | ||
| Filter | HEPASilent particle filter with washable fabric pre-filter | UltraHEPA with carbon/VOC filter and pre-filter (single filter unit) |
| Activated carbon | - | Yes |
| Replacement | F2MAX (110039) | AD4000 filter unit |
| Replacement cost | $69.99 every 6 months | $119.95 every 6 months |
| Yearly filter cost | $139.98/year | $239.90/year |
| CARB certified (ozone) | Yes | Yes |
| Controls and build | ||
| Air-quality sensor | particle | PM2.5 |
| Auto mode | Yes | Yes |
| Wi-Fi app | Yes | - |
| Fan speeds | 5 | 6 |
| Dimensions | 22.7 x 14.4 x 14.4 in | - |
| Weight | 16.2 lb | 15.8 lb |
| Warranty | 1 years | - |