Blueair 311i Max vs Sharp FP-K50UW for a bedroom or living room

Start with the room, because the two purifiers split there. I haven't run either one. The Blueair test results here are HouseFresh's. I couldn't find an independent test of the Sharp that I could open, so its figures are Sharp's own ratings, and that gap counts against it.

Size

AHAM Verifide's rule of thumb says CADR should be at least two-thirds of the room's area, so multiply a smoke CADR by 1.5 to get a room size under an 8 ft ceiling.

• Blueair 311i Max: rated smoke CADR 250 cfm, which gives about 375 sq ft (35 m²). HouseFresh's own test led it to recommend 330 sq ft (31 m²).
• Sharp FP-K50UW: rated smoke CADR 167 cfm, which gives about 250 sq ft (23 m²). Sharp's suggested room size is 259 sqft (24 m²), at 4.8 air changes per hour.

Sharp's store page also mentions 1,253 sq ft (116 m²). That figure assumes one air change per hour. Ignore it.

So a 14 by 16 ft living room, 224 sq ft (21 m²), fits either machine with the Sharp close to its limit. A 16 by 20 ft room, 320 sq ft (30 m²), is Blueair territory. Measure yours first, and count any open kitchen as part of it, since the EPA says to include the whole space the purifier serves.

Noise at the speed you'd actually use

On paper they're level. Sharp's spec sheet rates the FP-K50UW from 22 to 51 dBA, and Abt lists the Blueair from 23 dB to 50 dB.

HouseFresh measured the Blueair louder at 3 ft: 37 dBA at speed 1, 47.8 at speed 2 and 57.7 at top speed. Without a matching test of the Sharp, I can't tell you which is quieter in a real bedroom. The methods differ, so don't set 57.7 against Sharp's 51.

For a bedroom, what counts is airflow at low speed. HouseFresh estimates 108 cfm at the Blueair's speed 1, which I work out at about 160 sq ft (15 m²) with the two-thirds rule. Nobody I could read has published that number for the Sharp.

Ions

This one could settle it for some households. HouseFresh says the Blueair's ionizer produces small amounts of ozone and can't be disabled. Sharp's spec sheet lists its Plasmacluster ion modes as on or off, and claims under 0.01 ppm of ozone. That's Sharp's figure, not a test I read. The EPA warns that ionizers may have the potential to emit ozone, so I'd want that switch if anyone at home is wary of ozone.

Living with each one

The Blueair has auto mode and an app. The Sharp, per Abt, has neither auto mode nor Wi-Fi: three manual speeds, a timer and a button for a 60-minute boost. That's fine by a bed. It's a chore in a living room, where you'd want the fan to react to cooking.

Filters favor the Sharp on paper. Sharp says its HEPA and carbon filters last up to 2 years, depending on the environment, while Abt lists 6 to 9 months for the Blueair. HouseFresh counts $89.98 a year for the Blueair's. I didn't read a replacement price for the Sharp's two filters, so check it before you count the savings.

Shape matters in a tight room. Sharp's sheet gives 15.1 in wide, 8.2 in deep and 21.3 in tall, at 11 lb. That's slim front to back, but the pre-filter is on the back panel, so I wouldn't push it flat to a wall. Abt gives the Blueair as 19 in tall on a 12.5 by 12.5 in base, and it weighs 7.8 lb.

Money

Abt sells the Blueair at $229. The Sharp's $219.99 is the list price Abt shows as Comp. Value, checked November 2, 2026.

How I'd choose

I'd buy the Blueair for a living room up to 330 sq ft (31 m²), or for anyone who wants it to run itself. I'd buy the Sharp for a bedroom up to 250 sq ft (23 m²) if you want ions off and fewer filter changes.

I'd skip the Sharp above that size, and skip the Blueair if an always-on ionizer bothers you. For a larger room, go to air purifiers by room size. More detail on the Blueair is in my 311i Max review, and the two-thirds rule explained covers the arithmetic. You can also try your own floor area in the home sizer.