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Our pick for a medium room

Blueair Blue Pure 311i Max

US model; particle and carbon filter included

$229.99US price, checked Oct 13, 2026

Light, quiet purifier for rooms up to 439 ft², with $44.99 filters every 6 to 9 months

Check price at Blueair Full review →

Portable air purifier

Alen BreatheSmart 45i

US BreatheSmart 45i

$449US price, checked Oct 13, 2026

Slim, quiet HEPA purifier with a guarantee tied to Alen filters

Check price at Alen Full review →

Criterion	Blueair Blue Pure 311i Max	Alen BreatheSmart 45i
US price	$229.99Checked Oct 13, 2026 · Price details in the review	$449Checked Oct 13, 2026 · Price details in the review
Three-year ownership estimate	$499.93 Incomplete known subtotal. Not included: energy use.	$725 Incomplete known subtotal. Not included: energy use.
Choose if	A bedroom or office up to 439 ft² where you want low noise, app control and optional smoke or allergen filters.	You want a quiet, slim HEPA purifier for one large room and don't mind buying Alen filters every year.
Main trade-off	Filters run about $60 to $90 a year, and the three-year warranty depends on registering within 60 days.	Filters add $69 to $198 a year, and Alen gives its own airflow figure instead of AHAM smoke, dust and pollen ratings.
Key specifications	CADR (smoke, dust, pollen): 283, 314 and 365 cfm Room size: 439 ft² at 4.8 air changes an hour (one change every 12.5 minutes) Noise: 23 dB on low to 50 dB on high Power draw: 32 W; Blueair gives one figure, not a per-speed breakdown Filters: Particle + Carbon (standard), SmokeBlock or AllergenBlock, behind a washable fabric pre-filter Filter life and price: 6 to 9 months for the standard filter; $44.99 Particle + Carbon, $59.99 SmokeBlock, $64.99 AllergenBlock Controls: Speeds 1 to 3, Auto and Night; built-in air sensor; Wi-Fi app Size and weight: 19 × 12.5 × 12.5 (units not stated); 7.8 lb	Clean air delivery rate: 255 CFM on high by Alen's own CADRi figure; 80, 120 and 190 CFM on the lower speeds. No separate smoke, dust or pollen CADR on Alen's page. Room size: 950 sq ft at 2 air changes an hour or 1,900 sq ft at 1, by Alen's figures. Its FAQ says up to 1,600 sq ft. Noise: 24 dB on the lowest speed to 50 dB on high Power draw: 1.6 to 64 W in the spec table; the FAQ says 50 W on high. Alen doesn't say which setting draws 1.6 W. Filter life: Essential (Pure) 9 to 12 months; Advanced (Fresh) and Ultimate (Odor) 6 to 8 months, running 24/7 Filter price: $69, $89 or $99 each; 10% off on subscription ($62.10, $80.10 or $89.10) Ozone: Optional ionizer: under 0.001 ppm when on, 0 ppm when off. Alen lists CARB certification.
Exact variant	US model; particle and carbon filter included	US BreatheSmart 45i
Dimensions	19 × 12.5 × 12.5 (height × width × depth). Blueair doesn't give units, but the figures fit inches. It weighs 7.8 lb.	25 in high, 15 in wide and 8.5 in deep, and 14 lb, according to the product page. Alen's support table lists the 45i/FLEX at 19 × 11 × 28 in and 23 lb. That's the same size it gives for the shipping box.
Installation	No installation. It has a 360° intake and a top air outlet, and Blueair says you can place it anywhere. Wi-Fi and the Blueair app add schedules, an on/off timer and filter tracking. The product page gives no wall clearance.	Freestanding, with no installation. It runs from a 24 V external power adapter. The manual asks for a level surface at least 6 in from heat sources such as heaters, with the vents left clear. The Alen Air app adds remote control, scheduling and filter alerts over Wi-Fi.
Materials	A washable fabric pre-filter in four colors (Sand, Stockholm Fog, Moss, Limestone) covers the main filter. The standard Particle + Carbon filter pairs a particle layer with activated carbon that Blueair says traps light household odors. Blueair calls the system HEPASilent and says it combines electrostatic and mechanical filtration. SmokeBlock and AllergenBlock filters fit in place of the standard one.	One filter cartridge with a prefilter you can vacuum. Essential (Pure) is a True HEPA (H13) filter aimed at dust, pollen, dander, mold and allergens. Advanced (Fresh) adds activated carbon for VOCs, smoke and cooking odors. Ultimate (Odor) adds an odor neutralizer for pet and diaper smells. An optional ionizer can be turned on or off. The front panel comes in White, Oak, Weathered Gray, Brushed Stainless, Graphite or Espresso.
Warranty	One year against defects in material or workmanship. Register within 60 days, in your Blueair account or the app, and it extends to three years. Filters are covered for 30 days. Claims require that you've replaced filters on Blueair's schedule, with proof of purchase. Coverage is for the original owner only, and a unit exchanged during the extended term may be refurbished. If you bought it from another seller, you'll need proof of purchase. Blueair also says warranties aren't available from third-party resellers but doesn't define the term.	Alen gives a 1-year manufacturer's warranty. Its Forever Guarantee extends that if you register the serial number and use only Alen filters. You also need an active filter subscription or proof of an Alen filter purchase in the last 12 months. If troubleshooting can't fix a fault, you get a new unit in year two. From year three you get a refurbished or reconditioned unit, and the guarantee page sets no end date. Alen's support page says to register within 12 months of purchase. The guarantee doesn't transfer and excludes accidental damage, floods and fires. The product page says it needs an active subscription, but the guarantee page also accepts a recent filter purchase.
Returns	30 days from purchase for items bought directly from Blueair, with a prepaid return label. Filters and pre-filters taken out of their plastic wrap can't be returned. The $5 flat shipping charge and any other shipping charges aren't refunded. Processing takes 10 to 14 days. The refund then reaches your original payment method in 3 to 5 business days.	60-day trial on orders from alen.com. Alen refunds the purchase but deducts return shipping, using a FedEx label it emails you. Opened filters can't be returned. The refund can take up to 7 business days after the warehouse receives the return. Orders from other retailers go back through that retailer. Alen doesn't say whether the 60 days start at purchase or delivery.
Unresolved questions	Whether it's listed in AHAM's Verifide directory, which couldn't be read Whether CARB has certified it; the part of CARB's list that loaded showed only a different Blueair model Power draw on low and which speed the 32 W figure refers to Noise at speeds 2 and 3 Whether HEPASilent's electrostatic stage uses an ionizer; Energy Star lists it as fan and filter Which sellers Blueair counts as third-party resellers for the warranty Wall clearance and other setup guidance from the manual	Smoke, dust and pollen CADR from AHAM or Energy Star testing Whether CARB's own list includes the 45i (Alen's linked order file has no readable text) Average power on auto, so the yearly electricity cost Whether the store ships the original 45i or the touch-control 45i V2 named in Alen's CARB and Energy Star files The true size and weight, since Alen's product page and support table disagree How long a filter lasts if you don't run it around the clock How often subscription filters ship

These comparisons use published specifications, not head-to-head tests. Prices and terms are dated. Unknown costs are not zero. Check the exact variant before you buy.