Our verdict
Pick the Blueair Blue Pure 311i+ Max if your room is larger. Pick the Blueair Blue Pure 511i Max if you want the lower price.
The central trade-off
Rated room size. Blueair Blue Pure 311i+ Max: 525 sq ft; Blueair Blue Pure 511i Max: 237 sq ft.
Power draw. Blueair Blue Pure 511i Max states 20 watts; the other's maker page doesn't.
Filters. Blueair Blue Pure 311i+ Max: HEPASilent.
Filters. Blueair Blue Pure 511i Max: HEPASilent.
Price. When we checked, the Blueair Blue Pure 511i Max listed for less ($140 against $225); prices move, so check both buttons.
Side by side
| Specification | Blueair Blue Pure 311i+ Max | Blueair Blue Pure 511i Max |
|---|---|---|
| Rated room size | 525 sq ft | 237 sq ft |
| Smoke CADR | Not stated by the maker | Not stated by the maker |
| CADR | Not stated by the maker | Not stated by the maker |
| Quietest setting | Not stated by the maker | Not stated by the maker |
| Noise | Not stated by the maker | 48 dB |
| Power draw | Not stated by the maker | 20 watts |
| Filters | HEPASilent | HEPASilent |
| Warranty | 1 years | 1 years |
Values are the makers' published specifications. "Not stated" means the maker doesn't publish it.