Blueair Blue Pure 511i Max review

The Blueair Blue Pure 511i Max is a good small-room purifier for bedrooms, nurseries and home offices of up to about 237 sq ft. It's rated at just 17 watts, costs $29.99 per filter and comes with a capable app. At its $139.99 list price it's a harder sell than the Levoit Core 300S, which does nearly the same job for less with no ionizer. On sale (it has been listed around $95), the gap mostly disappears.

Which "511" is this?

Blueair sells two purifiers with 511 in the name, and they're very different:

• Blue Pure 511i Max: the one reviewed here. It has a particle sensor, auto mode, Wi-Fi and the Blueair app.
• Blue Pure 511: a cheaper, simpler model with no sensor, no auto mode and no app.

Amazon's listing titles end in "Blue 511i Max" and "Blue 511," so check the full title before buying. The 511i Max also takes over from the discontinued 411i Max, which Blueair's support site now points to as the replacement. You may see two room sizes for it: Blueair's support spec table still says up to 194 sq ft, while the current product page says 237 sq ft. Blueair explains that it updated CADR and room-size figures to meet new DOE standards, and the 237 sq ft figure matches the current 153 CFM smoke CADR.

How it performs in real rooms

The site's rule gives 153 × 1.55 = 237 sq ft. That fits a 12×15 bedroom (180 sq ft) with room to spare, or a 14×16 room (224 sq ft). It won't keep up with an open living room, and the "1,138 sq ft in one hour" claim on the box is the one-air-change marketing figure.

AirPurifierFirst's test is the best independent data available. Running at maximum in a 194 sq ft room for an hour, it cut PM2.5 from 104.8 to 8.3 µg/m³, a 92% drop. In a 320 sq ft room, beyond its rating, it still managed 90%. For comparison, the same reviewer recorded 94% for the Levoit Core 300S in the 194 sq ft test. In short, the two are close, and both are honestly sized for small rooms.

Since a bedroom purifier spends most of its life on low speed, it pays to size up when you can. If your room is closer to 230 sq ft than 150 sq ft, a bigger unit running quietly will beat this one running at full blast. Check your own room in the room size calculator.

Against the Levoit Core 300S

This is the comparison most buyers are really making:

The Blueair moves a little more air on a little less power, and its app is the more polished of the two. The Levoit Core 300S is cheaper and has no ionizer. If your only priority is clean air in a small bedroom, both work. Buy on price, or on how you feel about ionizers.

Filters and 3-year cost

The standard Particle + Carbon filter costs $29.99, and Blueair rates it at up to nine months. SmokeBlock and AllergenBlock versions are also available for this model. The washable fabric pre-filter is $8.99 if you want a spare or a new color.

Three-year math at the $139.99 list price:

• Filters: 3 replacements at nine-month intervals ($90), or 5 at six months ($150).
• Electricity: AirPurifierFirst measured 4.7 W on speed 2. Running 24/7, that's about $7 a year at $0.17/kWh. At its measured top-speed draw of 17.8 W, it's about $27 a year.
• Total: roughly $250 for a quiet bedroom unit with nine-month filters, and about $370 if it runs flat out with six-month changes.

That's among the cheapest smart purifiers to own, and the low power draw matters if it runs all night, every night. Try other intervals in the filter cost calculator.

Noise and nursery use

Blueair quotes 19 to 48 dB. AirPurifierFirst measured more: 40.1 dBA in sleep mode, 44.1 dBA on speed 2 and 61.6 dBA at maximum. Its meter tends to read high, too. It measured the 311i Max at 40.2 dBA in sleep mode, where HouseFresh measured 34.9. The pattern is still clear: quiet up to medium, loud at the top. The same reviewer also noted an odd noise at maximum speed, which it first suspected was a one-off but later heard from the 311i Max too.

For a nursery or child's room, the useful details are night mode (which dims or turns off the lights), a display lock so small hands can't change settings, and a rounded body with no sharp corners. It weighs 4.2 lb and measures 14.5 × 9.3 × 9.3 inches, small enough for a dresser or nightstand. For more quiet small-room options, see the best quiet air purifiers.

Smart features

The app handles fan speed, auto and night modes, display lock, schedules, indoor and outdoor air-quality readings, and RealTrack filter-life tracking, which estimates wear from fan speed, usage hours and pollution levels. "Welcome Home" uses your phone's location to switch the purifier on as you head home and off when you leave. It's handy if you're out all day, but a simple schedule does much the same thing. Alexa and Google Assistant control is supported. To clear the red filter light after a change, Blueair says to hold the fan-speed button for about 15 seconds until every LED lights up.

The catches

The ionizer can't be disabled. HEPASilent's electrostatic stage is part of how it gets 153 CFM from 17 W, but it's always on and produces small amounts of ozone. If that bothers you, the Levoit Core 300S is the obvious alternative. The background is in are ionizer purifiers safe.

Weak on odors. AirPurifierFirst found it struggled with strong cooking smells and wished it had pellet-based carbon. It also said the 511i Max isn't the best choice for homes with pets. The SmokeBlock filter helps with smells, but a purifier this size will never clear a litter-box room.

The sensor isn't the most precise. The same review called its air-quality sensor accuracy middling, so expect auto mode to react a bit late to a burst of dust.

Is it the right one for you?

Buy the Blueair Blue Pure 511i Max for a bedroom, nursery or office up to about 237 sq ft if you like Blueair's app, want minimal power draw, and can get it near its sale price. Register it within 60 days to extend the warranty from one year to three.

Choose the Levoit Core 300S if you want the cheapest well-proven small-room option with no ionizer. If your room is over 250 sq ft or has pets, step up to the Blueair Blue Pure 311i Max (about 439 sq ft) or the Coway Airmega AP-1512HH Mighty (about 361 sq ft), which can run quietly where the 511i Max would be working flat out. Budget shoppers can also compare the Levoit Core 200S-P.