The Alen 35i is the smallest and most affordable model in Alen’s premium lineup of air purifiers.
But ‘affordable’ is relative at $269 – especially considering that the 35i is significantly more expensive than small units from Coway and Levoit that promise similar performance.
So, what are you actually paying for? Is it just a brand name, or does this machine have any special features that make it worth the extra cash? To find out, we bought one ourselves and put it through the same tests I’ve performed on nearly 120 air purifiers to date.
The overall score for the Alen BreatheSmart 35i incorporates first-hand data results from our battery of tests, as well as our ratings for customer service, brand transparency, and design & UX. Check out the full scorecard below to see the split of categories.
Search for the 35i (or any other model you are researching) to see where it ranks:
The pros and cons of the Alen 35i
A summary of our top-level findings after testing this air purifier, following our methodology.
“If you can afford the $269 price tag, then the Alen 35i is one of the best small air purifiers I have reviewed.
In my experience, Alen makes air purifiers that you are buying for life. You’ll get excellent build quality, solid performance and a lifetime warranty if stick to OEM filters.”
HouseFresh Founder
& Lead Tester
CONS
PROS
| Clean air delivery rate (CADR): | – Top speed PM1 CADR: 162 cfm – Sub-45 dBA PM1 CADR: 101 cfm – AHAM dust CADR: 164 cfm |
| Filter technology: | Medical-grade H13 HEPA filter with optional pelleted activated carbon. |
| Recommended room size: | 247.5 sq. ft. (5 air changes per hour) |
| Dimensions: | 20.6 x 13 x 7.6 inches (52.32 x 33.02 x 19.30 cm) |
| Weight: | 11 lbs (5 kg) |
| Noise level in decibels from 3 ft. away: | Speed 1: 36.4 dBA Speed 2: 40.2 dBA Speed 3: 46.1 dBA Speed 4: 52.6 dBA |
| Electricity consumption in watts: | Standby mode: 0.29 watts Speed 1: 7.05 watts Speed 2: 10.25 watts Speed 3: 15.92 watts Speed 4: 31.14 watts |
| Filter lifespan: | 9-12 months |
| Manufacturer’s warranty: | Lifetime (with filter subscription) |
| Country of origin: | United States |
| Country of manufacture: | China |
Filtration technology
You can customize the choice of filter for your Alen 35i depending on whether you want to tackle particles or odors (or both).
You get to choose between three specialist filters — I went with the standard Pure filter, which is a HEPA H13 filter without carbon.
For removing particles and gases, you can go with the Fresh or Odor filters, both of which combine HEPA H13 with 0.5 lbs of activated carbon.
That said, be aware that a half-pound layer of carbon won’t be enough to tackle serious issues with chemicals like VOCs:
My favorite detail is the filter lock at the top that keeps the filter in place while creating a perfect, airtight seal.
This seal is also improved by the use of rubber around the filter, which stands out from the cheaper foam we see in other air purifiers.
By the way, if you want to remove mold spores or dust but don’t care about odors or gases, then the cheaper Pure filter will do the job you need it to do.
Design, controls and app features
A small air purifier with smart functions and an onboard laser particle sensor that is faster and more precise than the one you get in units from Coway and Levoit.
It looks like a shrunken-down version of its bigger siblings, the 45i and 75i:
Even though it’s the cheapest in the series, it still carries the same thoughtful design elements as the larger Alen devices.
It has a high-end laser particle sensor that you won’t need to clean, unlike optical sensors.
The sensor is fast and precise, triggering the LED ring at the top to go from blue (good) to purple (bad) in seconds.
The control panel is intuitive and gives you access to everything you need without the app.
You have clearly labeled buttons for the child lock, the lights, the multiple fan speeds, and the auto mode.
The 35i comes with app connectivity, which I know is not something everyone cares about but I was glad to see considering the price tag of this device.
Through the Alen Air App, you will be able to do all the useful things you’d expect. You can set timers, create custom schedules, and control your 35i from across the room via the virtual remote.
You can even get instant alerts on your phone the moment pollution spikes, and also see detailed graphs of the air quality levels in the room.
In fact, the 35i also has sensors for humidity, CO2, and tVOCs, so the app gives you a pretty good picture of air quality in your home.
Air cleaning performance
I tested the Alen 35i in our 728 cubic ft. test room, tracking how fast it removed all PM1 particles from the air after we filled the space with incense smoke.
When running at speed 4, our PurpleAir Zen sensor shows that the 35i needed 36 minutes to reach PM1 zero.
That’s a good time – a few minutes faster than the Coway Airmega 150 and the Levoit Vital 100S, and a massive jump over the popular Shark NeverChange HP150.
That said, both the AirFanta 3Pro and the Nukit Tempest Euro outperformed the 35i, showing the power of PC fan powered air purifiers.
Based on the natural ventilation of our test room, we estimate a PM1 CADR of 162 cfm. This makes the 35i powerful enough to provide five air changes per hour in rooms no larger than 247.5 sq. ft. when running at top speed.
I repeated the particle removal test with the Alen 35i running at each available fan speed, allowing me to estimate PM1 CADR at each fan speed:
Sound levels
I measured how much sound the Alen 35i generates at each fan speed from 3 ft. away – noise ranges from 36.4 dBA to 52.6 dBA at full speed.
The 35i hit 52.6 dBA at speed 4, making it noticeably quieter than the Coway Airmega 150.
Not only that, but it’s also a full 15 decibels quieter than the Oransi AirMend 150HB.
It generates 40.2 dBA at speed 2, and it took 58 minutes to reach PM1 zero in our test room.
This is a better performance than the other traditional small devices, but once again, it doesn’t come close to the small PC fan-powered air purifiers on the list.
Long-term running costs
Running an Alen 35i will cost you $107.30 per year, combining energy and filter replacement costs.
We used our energy meter to record how much electricity the 35i pulls at each fan speed and also while on standby:
At speed 4, the 35i pulls 31.14 watts and would add $35.30 to your annual electricity bill, assuming you run it 24/7 year-round.
That puts it right in the middle of the pack, cheaper to run than the higher CADR models from Oransi, AirFanta, and the midsize Levoit, but a few dollars more expensive than small, less powerful models from Coway, Shark and Levoit.
Alen recommends replacing the Pure filter every 9-12 months. A Pure filter costs $54, bringing your annual filter cost to $72.
When you combine this to the $269 upfront cost, the total cost to buy and run the Alen 35i for its first year reaches $376.30.
To put that in perspective, the more powerful AirFanta 3Pro would cost you just $327 in the first year. The popular Coway Airmega 150? Only $272… And even the larger Vital 200S has a cheaper year-1 cost at $291.
Bottom line: Should you get an Alen BreatheSmart 35i?
Our data shows that the Alen 35i is the most expensive in its class, both to buy and to own – does that make it the best small air purifier money can buy?
Based on the messages we get every day, it’s clear that many consumers want a small air purifier, which explains the trend we’re seeing of manufacturers releasing smaller models recently.
The problem is that many of these cute, small air purifiers are advertised as “quiet as light rain” and “suitable for large spaces,” yet our data shows that most are too loud and underpowered.
Not only that, small air purifiers are generally as expensive to run as larger devices because filters usually cost just as much, but they need replacing more often.
BUT, I know that some people want a small device or need something to help clean the air in small spaces.
If that is you, then you’ll get the most bang for your buck with the AirFanta 3Pro and more power with the Nukit Tempest Euro. Both of these are small devices and use quiet, energy-efficient PC fans.
However, I’ve heard from enough people who don’t like the look of PC fan air purifiers, or who just want a traditional device with smart features and an air quality sensor. If that is you, then you might want to look at the Levoit Vital 100S (left) or the Coway Airmega 150 (right).
However, investing in the Alen 35i could be worth the additional $100 when you consider that:
- It is quieter at top speed than every other air purifier we’ve benchmarked it against, except for the PC fan-powered 3Pro and the Tempest Euro.
- It also managed to outperform every other traditional air purifier when running at speed 2, making it the best performer at sub-45 dBA.
- It comes with a laser particle sensor, which makes the auto-mode more responsive, more accurate, and more useful than most.
So, if you can afford the $269 price tag or find it on deal, then the Alen 35i is one of the best small air purifiers I have reviewed, hands down.
It’s worth mentioning that, in my experience, Alen makes air purifiers you can buy for life. You’ll get excellent build quality, solid performance, and a lifetime warranty if you stick to OEM filters. My 10-year-old Alen A350 still works, and I can still buy filters from Alen even today!
And that’s it from me.
If you decide to get yourself a 35i, please use our affiliate link, as this will help me continue running this channel and buy and test more devices in the future. And if you have any questions, please drop them below in the comments section and I’ll reply as soon as I can.
