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Alen BreatheSmart 45i review

High-quality air cleaning coupled with low-impact noise and energy makes the 45i a smart choice.
Updated on April 14, 2024
Written by
Paul Allen
Paul is a staff writer for HouseFresh, with a focus on product recommendations and advice for smokers and apartment dwellers. He started writing in November 2020, when he joined the content production team at NeoMam Studios (our parent company).

Our verdict

Alen’s BreatheSmart 45i is a solid option for medium-sized rooms of 301 sq. ft. 


Powered by effective fans and medical-grade H13 HEPA filters, it comes with an impressive CADR score of 208 CFM. 


It does cost a little more than other units with a similar CADR, but in return, you get Alen’s impressive build quality, which is backed up by a lifetime warranty and a super-efficient unit that uses minimal energy and creates low operating volumes to allow for around the clock protection from pollutants.

Alen is one of the most respected names in the air purifier business. Based out of Austin, Texas, the company has been making top-of-the-range air-cleaning solutions for over 15 years.

In fact, the Alen 350 was one of the first air purifiers we tested over a decade ago and is still a device that stands up to many modern appliances. 

Alen has built on this pedigree to develop powerful purifiers suited to both commercial and residential settings. These days, their most popular product line is the BreatheSmart range, which includes the Flex, 45i and 75i

The BreatheSmart 45i is advertised as good for use in spaces as large as 800 sq. ft, making it the mid-range option from the line. The unit is equipped with a high-quality HEPA filter, a sleek design and smart features, not to mention Alen’s unrivaled lifetime warranty, so it certainly stacks up well on paper. Based on how well we know other Alen purifiers perform, it will be interesting to see what the 45i can deliver. 

As with all the products we review here at HouseFresh, we bought the Alen BreatheSmart 45i with our own money, and we have no ties with the manufacturer. As part of this review, we tested the air cleaning performance of the Alen 45i to assess how fast its fan can circulate the air and how well its filters.

The lowdown on the Alen BreatheSmart 45i

“The Alen 45i is aimed at those who are happy to pay for a well-made device that provides a lifetime warranty. It runs quietly for the level of power and has some great features with its auto-mode and app support. Alen has been around for many years, so this is a company you can trust, but there are better options if you just want best bang for your buck.”

—Danny Ashton, Founder & Senior Writer

No time to read the whole review? Here are my main takeaways from our hands-on review of the Alen BreatheSmart 45i. 

What we really like

Alen offers top-of-the-range filters, with an independently verified H13 HEPA filter included with the 45i as standard. 
The 45i is incredibly energy-efficient, keeping bills low even if you use the unit 24/7.
The purifier has various features that simplify operation, including an Auto mode, color-coded air quality feedback display and a smart app.
Alen makes high-quality units that come with a lifetime warranty (but you need an active filter subscription).
Low operating volumes and a pink noise hum make this a top choice for bedroom use.

What we think could be better

It is more expensive than other units with similar air cleaning power. 
The Alen app is a little buggy and could be improved.
Alen advertises the unit for spaces as large as 800 sq. ft., but it’s much more suited to spaces around 300 sq. ft to achieve more air changes per hour.

The specs

The BreatheSmart 45i currently retails for $419.00 and comes with an Energy Star-certified CADR of 194 CFM for smoke, 208 CFM for dust and 230 CFM for pollen. 

Other options on the market with a similar CADR include the Mila (263 CFM), which retails for $399.99, the Blueair Blue Pure 311+ (250 CFM), which will set you back $229.99 and the Levoit Vital 200S (245 CFM) which costs just $189.99, so it will be interesting to see what the premium price of the 45i provides in comparison.

HouseFresh rating:★★★★☆
Time to clean our 728 cubic feet test room (with the device running at top speed):34 minutes 
Air purifier technology:True HEPA H13 filters with activated carbon pellets + Ionizer technology
Recommended room size (4.8 air changes per hour):Up to 800 sq. ft.
Clean air delivery rate (CADR):Dust: 208 CFM
Smoke: 194 CFM
Pollen: 230 CFM
Dimensions (in inches / in cm):25H x 15W x 8.5D inches (63.5H x 38.1W x 21.6D cm)
Weight (in pounds / in kg):20.1 lbs (9.1 kg)
Filter life:12 months 
Noise level in decibels (measured from 3 ft. away with a sound level meter):Speed 1: 36.2 dB
Speed 2: 45.7 dB
Speed 3: 51.1 dB
Electricity consumption in watts (recorded with an electricity usage monitor):Standby mode: 0.8 watts
Speed 1: 4.4 watts
Speed 2: 7.4 watts
Speed 3: 15.2 watts
Speed 4: 25.3 watts
Estimated running costs (electricity consumption + official filter replacements):$105.40 per year
Cost per CADR cfm (based on dust CFM as reported by AHAM): $2.06
Manufacturer’s warranty:Lifetime (with product registration & active filter subscription)
Country of manufacture:China

The 45i is a serious unit with sophisticated features

Alen has managed to give a white box appliance a sleek style that shows off its quality.

The Alen BreatheSmart 45i is surprisingly stylish for a simple white purifier. Its glossy front is contrasted by a gun-metal grey trim and a capacitive control panel accented by colorful rings to indicate the current air quality in your room. 

It might not stand out of the crowd as much as the bold designs of Blueair or Coway, but this subtlety will definitely appeal to many. 

With a slender footprint and lightweight design, it also won’t take up too much space and can easily be transported from room to room. 


Not a fan of the pared-back aesthetic? Alen offers a range of design options, including Oak, Graphite and Espresso.

The touchscreen control panel is indicative of Alen’s impressive build quality. Not only does it look the part, but it’s highly responsive and easy to grasp at first glance.

From here, you can cycle through the 45i’s four fan speeds, turn the LED lights on or off, and lock the controls from meddling kids or pets.

You’ll also find the Auto mode setting, which utilizes an in-built air sensor to monitor particle levels and change the fan speeds and color-coded air quality display accordingly.

You can also switch on or off the unit’s ionizer depending on your preference. This technology releases positive and negative charges into the atmosphere, which causes particles to lump together, making it easier for the HEPA filter to capture.

The downside is that this technology can create a harmful byproduct known as ozone. Alen states that the 45i emits less than 0.001 PPM, which is less than what is naturally found in the atmosphere, so it shouldn’t cause too much of an issue, but I’m glad they still gave users the choice, unlike manufacturers such as Blueair.  

Those looking for more technical features will be glad to hear that the 45i is compatible with the Alen Air app. Through the app, you can adjust basic settings, receive notifications when it’s time to change the filter and check detailed reports on your space’s air quality. 

The app is straightforward to connect to and use, but it’s not without faults. Unfortunately, there is a delay in the air quality readings you see on the app and what is displayed on the device, with the app lagging behind significantly. I’ve also experienced the purifier disconnecting from the app numerous times and from reading reviews on the App Store, I see I’m not alone in this. 

Hopefully, these are bugs Alen can iron out in the future as having a functioning app is a super handy feature when you’re out of the home.

High-quality H13 HEPA filters to tackle tiny particles

Alen offers some of the best filters on the market, with different options to suit different needs.

Alen uses H13 HEPA filters to provide comprehensive protection from allergens, smoke and even bacteria and virus particles as small as 0.1 microns, with 99.9% effectiveness. 

Although we’ve seen a few rival manufacturers being called out for improperly advertising H13 filters without actually using them, it’s great to see that Alen has sent theirs to be independently verified by LMS Technologies.

Although the standard Pure filter doesn’t contain any carbon, you can upgrade to the Fresh, Odor or Smoke filter to increase levels of protection from VOCs. The latter contains an impressive 2.3 lbs of carbon inside, specifically designed to tackle the heavy particles found in wildfire or cigarette smoke.

Installing the filter couldn’t be simpler. Simply open the front panel and slot in the filter with the pre-filter facing you.


New filters will be delivered in a plastic wrapper. Be sure to remove this before installing it into your unit.

The Alen BreatheSmart 45i cleared our test room in 34 minutes

The results of our air cleaning performance, noise levels and airflow speed tests.

Here at HouseFresh, we test each and every air purifier that is featured on our site to see how well they perform against the smallest airborne particles, how much electricity they consume and how much noise they generate.

  1. In our home lab of 728 cubic feet, we light an incense stick to generate particle pollution and VOCs.
  2. We set up our trusted Purpleair Indoor Sensor with the latest Bosch gas sensor to track levels of PM1ug/m3, PM2.5ug/m3 and PM10ug/m3 and VOCs in the air.
  3. We switch the air purifier to its highest speed and measure how long it takes to get our room air quality down to PM1 level to 0.
  4. We use an energy meter to measure precisely how much electricity is used when running the unit at the lowest and highest fan speed settings.
  5. We track sound levels emitted by the air purifier at different fan speeds with the help of a commercial sound meter.
    sound meter

The first test is the air cleaning performance test. We fill our 728 cubic foot office with incense smoke and time how long it takes for the purifier to reduce all levels of PM1.0ug/m3, PM2.5ug/m3 and PM10.0 ug/m3 pollutants to zero, with the help of two PurpleAir air quality sensors: the PurpleAir Touch and the PurpleAir Zen.

It took 34 minutes for the Alen BreatheSmart 45i to clean the air in our test room:

What’s particularly interesting about these new results is that they were achieved using a generic filter from Pureburg, showing that you can still breathe the same level of clean air without forking out substantial amounts on genuine filters. 

Air cleaning speed test results compared

With the 45i set to its highest speed, we saw all polluting particles removed from the space in just 34 minutes.

This time is well below the average and matches other top air purifiers such as the Levoit Core 400S and Smart Air SA600. It beats the times set by Mila and Austin Air HealthMate but lags behind some of the more powerful purifiers, so it may be worth considering the Alen BreatheSmart 75i if you’re looking for an Alen unit to use in a larger space. 

Fan speed test results

How well an air purifier cleans the air often depends on its fan speed. The more powerful the fans inside the unit, the more air it will circulate and the more fresh air it will provide.

Armed with our Tetso 410 Anemometer, I was able to measure how much clean air was being expelled from the unit, with the BreatheSmart 45i pushing 1.25m of air per second on its lowest speed setting, 1.75m on speed 2, 3m on speed 3 and as much as 4m per second when running on turbo. 

This shows the 45i has lots of power under the hood and can spread clean air throughout your space. 

Noise levels test results

Being able to use your air purifier with minimal distraction is paramount, as we’ve found noisy units get used far less often.

When recording the decibel levels created by the 45i, I was really impressed by how quiet it operated at both ends of the spectrum, creating 36.2 dB at its lowest speed and 51.1 dB when used on turbo.

This makes the Alen unit one of the quietest purifiers we’ve tested and an excellent option for light sleepers. Alen even claims the frequencies created at this volume can be classed as pink noise and may help you drift off thanks to its calming background hum.  

As a light sleeper myself, I wasn’t bothered by the noise generated by the unit and would certainly recommend the 45i for use in a bedroom or a similar quiet environment. 

To hear how loud the 45i operates for yourself, be sure to check out our sound guide below. 

The cost to run an Alen BreatheSmart 45i: $105.40 per year

1. Electricity costs = $36.40 per year

As energy prices soar around the world, it’s never been more important to check how much electricity your new appliance will use. 

Using our wattage monitor, we saw that the Alen BreatheSmart 45i was uber-efficient, drawing just 3.9 watts at its lowest speed, 6.9 watts at speed 2, 14.4 watts at speed 3 and 24 watts on turbo mode. Even with the ionizer activated, this consumed less than 1 extra watt at each speed setting, which was equally impressive. 

Using the Department of Energy’s energy calculator, we could then estimate running costs based on using the device at top speed 24 hours a day, 365 days a year. The total cost came to just $26.28 per year, which equates to just over 50 cents per week, a small price to pay for pollutant-free air. 

2. Filter costs = $69.00 per year

Another key cost to consider is filter replacements. The 45i uses mechanical filters, including HEPA and activated carbon, which, over time, will become saturated with pollutants, lose efficiency and need replacing.  

Costs range from $69.00 for the Pure filter to $119.00 for the Smoke filter. These are expensive compared to other manufacturers; however, with a certified H13 HEPA and large quantities of carbon available, you can rest assured you’re buying a quality product. 

Alen also states that their filters will last around 9-12 months if used continuously. This is a longer lifespan than cheaper rivals such as Winix or Levoit, so costs may even out in the long term.  

Alen Air Filter B4-Pure Replacement H13 True HEPA Filter for BreatheSmart 45i & Flex Air Purifier – Captures Allergens, Dust, & Mold (1 Filter)
  • HEPA AIR FILTER: Breathe cleaner air with the Alen Air Purifier’s high-quality HEPA filter. This advanced filter captures allergens, dust, mold, and germs, promoting a healthier and safer environment for you and your loved ones.
  • MEDICAL-GRADE H13 TRUE HEPA FILTER: Discover the exceptional power of our medical-grade H13 True HEPA filter within your home. Our filter captures 99.9% of airborne particles as small as 0.1 micron, this technology provides clean and fresh air throughout your space. Take control of your indoor air quality and create a safe haven for your family.
  • HASSLE-FREE MAINTENANCE: Convenience made simple. Our Air Filter Replacements feature an easily removable pre-filter screen. Effortlessly clean your replacement filter using a vacuum ensuring optimal performance and extending its lifespan. Save time and effort while enjoying consistent air purification in your home.
  • EXTRA LONG LASTING: Say goodbye to frequent filter replacements. Our filter has a 9 to 12 months lifespan. Enjoy continuous and hassle-free air purification without the worry of constantly replacing filters.
  • EFFICIENT FILTER PERFORMANCE: Experience efficient performance with our Alen Air Purifier Filters. The unique design of our H13 True HEPA Medical-Grade Filters includes foam on the outside of the frame, which ensures exceptional effectiveness without any air leaks. Maximize airflow while capturing even the most stubborn particles, achieving a thorough and comprehensive clean.

It’s also worth mentioning that there are lots of generic filters available online that can reduce filter replacement costs considerably. We tested the $36 Pureburg, a replica of Alen’s Pure filter, and delivered the same cleaning performance. But remember, Alen’s lifetime warranty is only valid if you have a genuine filter subscription. 

PUREBURG Flex True HEPA Replacement Filter Set Compatible with Alen 45i / Flex BreatheSmart Air Purifier,Part Number B4-Fresh / FL40-Silver-Carbon,H13 4-Stage Filtration Activated Carbon Air Clean
  • High-quality Replacement Filter Pack (1 H13 True HEPA + 4 Carbon Pre-Filters)
  • Fully Compatible with Alen 45i / Flex BreatheSmart Air Purifier , Part Number: B4-Fresh / FL40-Silver-Carbon
  • H13 True HEPA capture up to 99.97% of airborne particles as small as 0.3 microns. This includes dust, pollen, pet dander, smoke, and other minute particles ,Activated carbon reduce Chemicals VOCs, tobacco smoke, PM2.5,common household bad smell,Also Prevents large particles such as dander,Pet hair
  • Please replace regularly to keep your machine fresh and clean,For best results, remove the filter once a month and clean with a soft brush or gently vacuum.
  • Top-Notch Quality Used for Maximum Customer Satisfaction Guaranteed, Change the PUREBURG replacement filter in minutes, no tools required; note: please remove the new filter from the plastic bag before placing it into it.

Bottom line: Should you buy an Alen 45i?

A worthy investment that delivers efficient air cleaning without the drawbacks of other units. 

The BreatheSmart 45i is an excellent option due to its impressive build quality, top-of-the-range filters and robust air circulation.

I’m also a huge fan of its low operating volumes and impressive energy efficiency, which enable you to reap the rewards of clean air around the clock without incurring expensive bills or distracting volumes. 

Although this unit was beaten in our speed test by the Blueair 311+ and Levoit Vital 200S, it is worth pointing out that the 45i has an optional ionizer, whereas the Blueair does not. Alen also uses certified H13 HEPA filters, whereas the Levoit unit still has question marks over its certification. 

The 45i is a well-built device from a trusted manufacturer. While its $430 price tag might put off some consumers, its unique lifetime warranty and certified HEPA filters could make this a good air purifier for others.


We calculated yearly costs associated with running Alen BreatheSmart 45i for 24 hours a day for 365 days. We ran this calculation utilizing the U.S. average utility rate of $0.173/kWh as of March 25th, 2024.

Last update on 2024-04-19 / Affiliate links / Images from Amazon Product Advertising API

About the author

Paul Allen

Paul is a staff writer for HouseFresh, with a focus on product recommendations and advice for smokers and apartment dwellers. He started writing in November 2020, when he joined the content production team at NeoMam Studios (our parent company).