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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 →

Our pick for a small bedroom or office

Blueair Blue Pure 511

US model, store item 109994, with one Particle + Carbon filter and an Arctic Trail pre-filter

$99.99US price, checked Oct 13, 2026

Low-cost purifier for one room up to about 190 ft², with filters at $48 a year

Check price at Blueair Full review →

Criterion	Alen BreatheSmart 45i	Blueair Blue Pure 511
US price	$449Checked Oct 13, 2026 · Price details in the review	$99.99Checked Oct 13, 2026 · Price details in the review
Three-year ownership estimate	$725 Incomplete known subtotal. Not included: energy use.	$243.93 Incomplete known subtotal. Not included: energy use.
Choose if	You want a quiet, slim HEPA purifier for one large room and don't mind buying Alen filters every year.	A bedroom or office up to about 190 ft² where you want a cheap, simple purifier with low filter costs.
Main trade-off	Filters add $69 to $198 a year, and Alen gives its own airflow figure instead of AHAM smoke, dust and pollen ratings.	It covers only one small room, and it has three manual speeds with no air sensor or auto mode.
Key specifications	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.	CADR (smoke, dust, pollen): 122, 123 and 123 cfm Room size: 189 ft² at 4.8 air changes an hour (one change every 12.5 minutes) Noise: 24 to 49 dB in the spec table; 22 dB on low and 44 dB on high in the FAQ Power draw: 16 W, a single figure with no low or high Filters: One Particle + Carbon filter behind a washable pre-filter Filter life and price: About 6 months; $23.99 per filter, $6.99 per pre-filter Controls: Three manual fan speeds and a filter-change light; no air sensor Size and weight: 13.4 × 7.9 × 7.9 in; 4.2 lb
Exact variant	US BreatheSmart 45i	US model, store item 109994, with one Particle + Carbon filter and an Arctic Trail pre-filter
Dimensions	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.	13.4 × 7.9 × 7.9 in (height × width × depth). It weighs 4.2 lb.
Installation	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.	None. Plug it in and it blows clean air out the top. Blueair's page links no manual, so it doesn't say how much wall clearance it needs.
Materials	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.	A single Particle + Carbon filter sits behind a washable pre-filter. Blueair says the filter captures PM2.5, pollen, dust mite allergen and pet dander allergen. The carbon is aimed at light household odors such as smoke and cooking. Blueair calls the system HEPASilent, a mix of electrostatic and mechanical filtration. Pre-filters come in Arctic Trail, Night Waves and Winter Reed.
Warranty	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.	One year from purchase, or two if you register. Blueair's warranty page gives 60 days to register, in your Blueair account or the app. That page doesn't name the 511, so the two-year term comes from the product page. You need to replace filters on Blueair's schedule and keep proof of purchase. Coverage is for the original owner only, and warranties aren't available through third-party resellers. In the first year a defective unit is exchanged for a new or equivalent one. During the registered extension, the replacement is refurbished. Coverage ends if the unit leaves the continental US or Canada. Filters are covered for 30 days.
Returns	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.	30 days from purchase for items bought directly from Blueair, sent back with Blueair's prepaid label. Filters and pre-filters that are used or out of their plastic wrap can't be returned. Shipping charges, including the $5 flat rate, aren't refunded. Blueair takes 10 to 14 days to process a return. The refund then reaches your original payment method within 3 to 5 business days.
Unresolved questions	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	Whether it's listed in AHAM's Verifide directory or Energy Star's product finder; neither directory could be read Whether CARB has certified it; the part of CARB's list that loaded showed four other Blueair models Power draw on low, and which speed the 16 W figure refers to Noise at speed 2 Whether the electrostatic part of HEPASilent gives off any ozone Wall clearance and other setup guidance from the manual

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.