Our verdict on the Alen BreatheSmart 35i
Worth comparing for a bedroom or office: the 35i has published 190-cfm CADR, automatic particle sensing and a compact footprint. Compare its filter options and noise at your actual fan speed. Its large advertised one-hour room-size claim is not the same as rapid cleaning of that entire area.
Review methodology and model notes
Alen BreatheSmart 35i reviewed using manufacturer specs and original Yawnder observations, with model-specific comparison to the 75i.
No new controlled CADR, decibel or health-outcome testing. How we review products.
Alen BreatheSmart 35i and 75i: real product photos
Current Alen BreatheSmart 35i specifications
| Published CADR | 190 cfm (manufacturer) |
|---|---|
| Sensor and fan | Particle sensor, Auto mode and four selectable fan speeds |
| Recommended room context | Alen markets up to 1,400 sq ft over one hour; select by CADR and required air changes, not the maximum marketing area alone |
| Size and weight | 20.6 × 13 × 7.6 inches, approximately 10 pounds |
| Noise | Manufacturer support gives approximately 21–42 dBA; Yawnder did not remeasure it |
| Filter lifetime | Pure often 9–12 months; Fresh with carbon around 6–8 months; actual use varies |
| Replacement cost | Essential Pure from approximately $54 on the manufacturer catalog when checked |
| Warranty | Forever Guarantee subject to registration and continuing genuine-filter purchasing/subscription requirements |
35i official product listing · Alen technical support specifications · Warranty requirements.
Earlier review notes
The earlier Yawnder write-up described straightforward setup, easy access to the filter, a quiet low setting and an automatic mode that adjusted to changes in the particle sensor. It also said the unit was displayed at the showroom at the time; call ahead to check current availability. We do not have documented measurements of room particle reduction or clinical outcomes for this review.
Room size, sound and controls
Alen’s current product page lists a CADR of 190 cubic feet per minute, four fan speeds and a particle sensor. It describes coverage of up to 700 square feet every 30 minutes or 1,400 square feet every hour on its stated conditions. Those figures reflect different air-change rates, not a guarantee for every room; cleaning falls at lower speeds.
Using the EPA’s approximate sizing chart for an eight-foot ceiling, 190 cfm is close to the recommended smoke CADR for about 290 square feet. Higher ceilings, open plans, lower fan speeds and the particular pollutant can change the sizing decision.
Alen’s product page lists sound levels of about 21 dBA at the lowest speed and 42 dBA at the highest on Alen's current support page. Its separate support page lists a different low-speed value, so treat these as manufacturer figures and check the current specification for your unit.
Filters and replacement costs
Alen lists multiple particle-filter options, including choices with carbon for odors and certain gases. Particle filtration and gas adsorption are different functions; the effectiveness of carbon varies with its amount and the pollutant. Check the current filter price and replacement interval for the option you choose.
The manufacturer estimates replacement at roughly 6–12 months depending on filter and use. Follow the model’s instructions and monitor conditions rather than assuming every filter lasts the same amount of time.
Warranty and use
Alen’s product listing describes its Forever Guarantee as requiring registration and an active filter subscription. Check the current warranty terms and exclusions before buying. The manufacturer says the 35i has no ionizer.
Air cleaning can reduce airborne particles, but it does not replace ventilation, source control or treatment for a health condition. It will not fix the moisture problem that causes mold.
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Comparing the 35i with other purifiers
Compare smoke CADR at the speed you can tolerate, filter replacement cost, warranty requirements and the physical footprint. Our Alen 75i guide covers a larger model with different airflow and filter costs. Neither model’s advertised room size alone tells you whether it will meet a particular room’s needs.
Alen 35i vs. 75i
Compare the 35i's published 190-cfm CADR with the 75i's published 347-cfm CADR. The 75i is larger and uses more expensive replacement filters, while the 35i can make sense in smaller rooms. Neither unit should be selected on a maximum square-footage label alone.
Frequently asked questions
What is the 35i’s CADR?
Alen currently lists 190 cfm. Compare the relevant particle CADR with your room size and intended fan speed.
Does it remove gases as well as particles?
Particle filters capture airborne particles. Some filter variants add carbon for certain odors and gases; performance depends on the filter and pollutant.
Does the warranty require a subscription?
Alen’s current product listing specifies registration and documented genuine-filter purchases or a qualifying filter subscription under the current program terms. Check the current policy before purchase.
Can it replace ventilation?
No. The EPA recommends air cleaning alongside ventilation and controlling pollutant sources.
Final verdict
Alen BreatheSmart 35i is a credible choice to compare for a smaller room when you value auto mode, replaceable filter options and a relatively compact shape. Check the actual smoke CADR, your room volume, the replacement-filter cost and the specific warranty conditions. The original Yawnder observations remain qualitative, not controlled medical or filtration test results.
Yawnder may earn commission from eligible outgoing links. Model specifications and policies can change. Original reviewer notes do not imply clinical efficacy or standardized performance results.