Name: Blueair Blue Pure 311i Max
Brand: Blueair

Abt's listing for the Blue Pure 311i Max gives four room sizes: 1,054 sq ft (98 m²) in its headline, 929 sq ft (86 m²) in its quick specs, a recommended 439 sq ft (41 m²) in that same headline, and 387 sqft (36 m²) in the product text and footnotes. They can't all guide a purchase.

I'd plan around 330 sq ft (31 m²), and less for a bedroom. I haven't run this purifier myself. The test results below are HouseFresh's, from a review dated February 12, 2026, and the ratings are Blueair's as Abt lists them. My score is an opinion on that evidence.

Where the room size comes from

AHAM Verifide's rule of thumb says a purifier's CADR should equal at least two-thirds of the room's area. Run that backward and a rated smoke CADR of 250 cfm covers about 375 sq ft (35 m²) under an 8 ft ceiling. The EPA's chart lands in the same place, asking for 195 cfm at 300 sq ft (28 m²) and 260 cfm at 400 sq ft (37 m²).

HouseFresh's result comes in lower. At top speed the unit took 27 minutes to reach zero PM1 in a 728 cubic ft test room, and HouseFresh estimates a PM1 CADR of 220 cfm from that. Its recommended room size is 330 sq ft (31 m²) at 5 air changes per hour. That's a different test from AHAM's, aimed at the smallest particles, and I still trust it more for planning.

One loose end. HouseFresh quotes an AHAM dust CADR of 321 cfm, while Abt's page shows 250 cfm. I can't reconcile those from the pages I read, so I size from smoke.

Three things shrink the answer further:

Wildfire smoke. AHAM recommends a smoke CADR equal to the room's square footage, which caps this unit near 250 sq ft (23 m²).
High ceilings. AHAM says to go up a size above 8 ft and gives no multiplier.
Open plans. The EPA says to count the whole space the purifier serves. A living room that opens onto the kitchen is a bigger room than the tape says.

Measure the open area, not the rug.

Quiet speeds serve a smaller room

The EPA notes that CADR is typically measured at a purifier's highest speed, and nobody sleeps next to top speed. HouseFresh's sound meter, 3 ft away, read:

Sleep mode: 34.9 dBA
Speed 1: 37 dBA
Speed 2: 47.8 dBA
Top speed: 57.7 dBA

Blueair's rating, on Abt's page, runs from 23 dB to 50 dB. A footnote there describes that top figure as sound pressure in an assumed 387 sq ft room, so the method differs from HouseFresh's. I wouldn't call the rating false. I'd just plan on the higher number.

The airflow at those quieter speeds decides the fit. HouseFresh estimates 108 cfm at speed 1 and 185 cfm at speed 2. Applying AHAM's two-thirds, which is my arithmetic and not HouseFresh's, that's about 160 sq ft (15 m²) and 275 sq ft (26 m²). A 12 by 13 ft bedroom is 156 sq ft (14 m²), right at the limit for speed 1. HouseFresh's reviewer says speed 2 is louder than he'd like.

What you take on with it

Filters are the main running cost. Abt lists a change every 6 to 9 months. HouseFresh assumes a new filter every six months and reaches $122.19 a year with electricity, at top speed around the clock.

The ionizer is the part I'd think hardest about. HouseFresh says it's built into Blueair's HEPASilent system, produces small amounts of ozone and can't be disabled. The EPA warns that ionizers may have the potential to emit ozone. If that bothers you, stop here.

Odors are the other weak spot. HouseFresh says the lack of pelleted activated carbon leaves it "pretty useless for VOCs", and the EPA points out that CADR covers particles only.

Handling is easy. It weighs 7.8 lb, stands 19 in tall on a 12.5 by 12.5 in base according to Abt, and has no wheels. HouseFresh reports the app worked without trouble, though the optical sensor needs regular cleaning.

Which home I'd put it in

It costs $229 at Abt, checked November 2, 2026.

I'd buy it for an apartment with a closed living room of 250 to 330 sq ft (23 to 31 m²), where it can run at speed 2 while people are awake. It also works in a bedroom up to about 160 sq ft (15 m²).

I'd skip it for an open-plan floor above 375 sq ft (35 m²), for cooking smells or VOCs, or if you want an ionizer you can switch off. The Sharp lets you do that, and the Blueair 311i Max against the Sharp FP-K50UW sets out the trade. For more floor, see air purifiers sorted by room size. If the two-thirds rule is new to you, what CADR means walks through it, and the home sizer will run your own numbers. The 311i Max product page has the full spec list.