Blueair Blue Pure 211i Max vs Blue Pure 511i Max

The Blueair Blue Pure 511i Max and Blue Pure 211i Max are built for very different roles within Blueair's lineup. The 511i Max is designed for smaller bedrooms, home offices, and other compact spaces where quiet operation and a small footprint matter most, while the 211i Max is built to move substantially more air through larger bedrooms, living rooms, and open-concept areas. The larger model delivers much stronger particle filtration, a higher CADR, and better air-cleaning performance at quieter settings, making it a better fit for larger spaces. The trade-off is size and noise: the 211i Max is considerably bulkier and gets noticeably louder at higher fan speeds. For a bedroom or any space that doesn't require heavy-duty coverage, the 511i Max is the more practical fit. For larger rooms where air-cleaning performance comes first, the 211i Max is the obvious step up.