Blueair Blue Pure 311i Max vs Blueair Blue Pure 511i Max

The Blueair Blue Pure 511i Max wins overall on price, since the two tie on filtration, sensors, connectivity and integrations. The Blueair Blue Pure 311i Max earns the better owner feedback and covers a bigger room, so it is worth the step up for spaces beyond about 237 ft².

Room size. The Blueair Blue Pure 311i Max is rated at 283 CFM for up to 439 ft², the Blueair Blue Pure 511i Max at 153 CFM for up to 237 ft². The 311i also has a screen on the unit, while the 511i relies on an air quality light.

The Blueair Blue Pure 511i Max is listed at 17 W and the Blueair Blue Pure 311i Max at 32 W at top speed, so the smaller model is the more frugal one on paper, as you would expect from a machine moving less air.

Both use HEPASilent filtration with activated carbon and a washable fabric pre-filter, rated for 9 months, and both read PM1, PM2.5 and PM10 to drive auto mode.

Shoppers who want the lowest cost way into Blueair's app, sensors and filter for a small bedroom or office.

Anyone with a room up to about 439 ft², or who values a better reviewed unit with an on-device screen.