Alen BreatheSmart 45i Review – Hands-on Air Purifier Test

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Alen BreatheSmart 45i Air Purifier

Our Rating:

Key Features:

H13 True HEPA

Auto-mode for Hands-off Operation

Real-time Air Quality Monitor

More Compact

Powerful Smart Air Purifier Built for 24/7 Use

Alen has always delivered reliable, highly usable air-purifying products. Their 75i purifier rivals the cleaning power of most other options we’ve looked at. But it’s a large unit that takes up a lot of space.

That’s where the new generation BreatheSmart 45i air purifier comes in. This more compact version has a smaller square footage rating but still works impressively hard to keep your air clean.

Best of all, it has the same great smart features and modes as the original, including a real-time air quality monitor. This highly useful mode allows for hands-off use and delivers superior air quality 24/7.

Review Criteria Ratings

Air Purifying Performance4.5/5
Build Quality5/5
Maintenance and Upkeep5/5
Operating Costs5/5


  • H13 True HEPA removes 99.9% of particles under 0.1 microns
  • Accurate auto-mode setting for hands-off operation
  • Real-time air quality feedback with wifi connectivity
  • Ultra-quiet, lights-out option
  • Ozone-safe ionizer option


  • Still bulkier than the competition
  • Standard filter lacks odor control
  • Sucks power even when powered off

Should You Buy It?

If you want unparalleled air purifying performance that you can see, there is no better option than Alen.

Compared to the 75i, the 45i gives you the same reliable operation and range of modes for a smaller room, while costing less and taking up less space.

Disclosure: It is important you understand that we may receive commissions when you click our links and make purchases. However, this does not impact our reviews and comparisons. All opinions are our own we pride ourselves on keeping our articles fair and balanced. For more info see our disclosure statement.

The Quick Alen BreatheSmart 45i Details

Please find below a brief table outlining the key specifications of the Alen 45i Air Purifier. The information presented is based on empirical data obtained through our rigorous testing conducted in real-life situations.

Marketed Room Rating (Calculated Room Rating)800 sq ft (380 sq ft)
Energy Use36 watts on high
Filter TypeH13 HEPA with optional upgrades
Base Filter Cost$69
Recommended Filter Change Time9-12 months
Noise Level (low/high)28.8 dB / 53.9 dB
Real-Time Air Quality Monitor?Yes

Alen BreatheSmart 45i Air Purifier Overview

The Alen 45i is the second air purifier in the company’s newest line. We’ve already had the pleasure of reviewing the larger model, the Alen 75i air purifier, and found many things to love about it.

Both the 75i and 45i feature the same sleek, upright build with side air intakes. This allows for easier placement as the units can be set against the wall. This newest unit is 2 inches shorter, 3.5 inches narrower, and 12 pounds lighter than its predecessor.

alen 45i next to the 75i

While its smaller size makes it easier to place inside the home, it also means the 45i is less powerful. While the 75i has a CADR of 347 and a square footage rating of 1300 square feet, the 45i has a CADR of 245 and is only rated for rooms up to 800 square feet.

This smaller unit has the same wifi connectivity as its predecessor. It can be used with the same smartphone app for wireless monitoring and control wherever you are.

It features a real-time, color-coded air quality monitor that tells you how clean your home’s air is at any moment. This feature works with the auto-mode function to automatically adjust the fan speed to clean air faster when needed. The unit also has three light settings, a filter reminder, and a lock feature.

The filter options for the 45i are smaller versions of what is available for the 75i. The standard “Pure” filter is a true HEPA rated to remove 99.9% of particles smaller than 0.01 microns. You can also opt for upgraded filters that tackle odors, VOCs, and smoke.

side view of Alen 45i Air Purifier

To further the unit’s cleaning power, there is also a built-in, ozone-free ionizer.

I had the chance to put all of these great features to the test in my own home. Find out what I liked about the 45i and where it fell short by reading my full Alen BreatheSmart 45i Air Purifier review, below.

How The BreatheSmart 45i Performs

Alen 45i unpackaged

I received a new Alen 45i to review in my own home. As I do with every air purifier I get for review, I tested this one for air purifying performance, energy use, noise output, and more. 

Air Purifying Performance

Alen claims the 45i has a room coverage rating of 800 square feet. As usual, this number is a little bloated. 

According to the CADR to room size ratio recommended, a more appropriate room size rating for this unit would be 380 square feet. We get this number by multiplying the unit’s CADR, 245, by 1.55.

When used in spaces closer to this size, the 45i performs impressively well.

I tested my BreatheSmart 45i against common air quality problems including:

  • smoke
  • pet odor
  • and VOCs

With the standard “Pure” filter installed, it did a great job removing noticeable particles and improving air quality. In all instances, however, there were lingering odors that were not picked up by the air quality monitor or filtered out by the unit.

This makes sense considering the standard filter lacks the activated carbon needed to neutralize these smaller particles. What the filter did do well with, however, were large particles like allergens, pollen, dust, and visible smoke.

To test how quickly the unit cycles out pollutants, I did my standard oil lamp test. By lighting and extinguishing oil lamps in a confined space, I was able to propel the air quality to the maximum reading of 499, according to my Alen Air Quality Monitor.

I then set the 45i to auto mode and left it sealed in the 150-square-foot room to see how long it would take to return the air quality to a value of 1.

After 15 minutes, the air quality had already dropped to 90. After 30 minutes, it was down to 10. The air returned to excellent condition after 46 minutes.

Overall, my test results back the air cleaning performance claims of the 45i. It appears to work just as well as the 75i when placed in size-appropriate spaces.

Build Quality

Breathesmart 45i dismantled

There is a lot to love about the physical build of this unit. Like the 75i, it features a magnetic filter panel that is easy to take off and put on without the risk of snapping small plastic pieces. 

These panels are also customizable. They come in six different colors from oak to brushed stainless to better match your home decor.

Overall, the build quality seems high on this little unit. The touchscreen control panel works effortlessly, all pieces feel durable, and the carrying handle on the back is a nice touch. I also like that the cord wraps around the bottom for easy storage.

My only complaint is that the unit is still a bit bulky compared to other units rated for the same square footage. It is too big to be placed on a table or nightstand. On the floor, it has a much lower profile than the 75i but still takes up a decent amount of space.

Maintenance and Upkeep

rear of breathesmart 45i

The replacement filters for the 45i are smaller and therefore a little cheaper than the 75i. But they also don’t last as long. 

The standard “Pure” filter costs $69 while the most expensive “Smoke” filter costs $119. 

The manual recommends filter changes every 9 to 12 months with consistent use. This is less than the 12 to 15 months recommended for the larger unit. 

Still, a year-long lifespan for an air purifier filter is almost unheard of. While the filters are a bit pricey, the overall cost of maintenance is on the cheaper side considering how infrequently you’ll have to change the filter.

Other upkeep is limited to wiping the unit down to keep it clean and dust free.


alen breathesmart 45i air purifier control panel

The Alen 45i has four fan speeds. The lowest is impressively quiet while the highest speed is noticeable, but not annoying.

According to the marketing information, the low setting puts out 23 dB while the high setting puts out 49 dB. According to my tests, these numbers are a little low. 

When I ran the unit on low I recorded a noise output of 28.8 dB. On high, I got 53.9 dB.

Either way, this is certainly not the loudest air purifier I’ve reviewed. And on the lower settings, it is quiet enough to sleep with. And the noise is smooth and even once it reaches the set speed.

If you plan to use your air purifier in the bedroom, you’ll be happy to know there are multiple light settings. The control board and air quality monitor lights can be set to dim, high, or off, depending on your needs.

But what truly makes this one of the most usable air purifiers is the auto-mode. This mode uses the input of the real-time air quality monitor to adjust the fan setting for optimal cleaning performance. You can literally set this mode and not have to touch the unit again until the filter needs to be changed.

The unit is designed to run 24/7 on auto mode for optimal performance. Once I had mine going for a few hours, I completely forgot about it. For truly hands-off air quality care, it doesn’t get much easier than that.

Operating Costs

Alen Breathesmart 45i air purifier during product testing

The Alen BreatheSmart 45i air purifier is Energy Star Certified. The manual claims it uses between 1 and 50 watts depending on the setting. I tested the energy use of my unit using an outlet-watt meter.

On low, the unit used an average of 3.8 watts. On high with all the lights on, that number went up to 36 watts.

Even if you were to run this unit on high 24/7 for an entire month, your energy bill would only go up by about $3.10 on average. On auto mode, you could expect to pay less than a dollar extra per month. That’s not bad at all considering what this powerful unit delivers.


The Alen 45i is a powerful home air purifier with a ton of great features. But if you’re looking to get a little more bang for your buck or a more simplified unit, there are other options.

For serious cleaning power that can handle larger spaces, the Hathaspace HSP002 is worth a look. Compared to the BreatheSmart 45i, it has a higher CADR rating, a quieter lowest speed, and is better suited for larger spaces. Much like the Alen 45i, it has a built-in air quality monitor with a color-coded read-out and a useful auto-mode function.

If what you really want is a simple air purifier that costs less while delivering cleaner home air, the Okaysou Apollo 630 is a great choice. Compared to the Alen 45i, it has a lower CADR but a similarly powerful True HEPA filter that includes activated carbon for better odor and VOC control. The simple control panel has useful options like a timer mode and three fan speeds, and the entire unit comes in at a price point to fit any budget.

Product TitleAlen 45i
Alen 75i
Hathaspace HSP002
Okaysou Apollo 630
Product TitleAlen 45i
Alen 75i
Hathaspace HSP002
Okaysou Apollo 630
Marketed Room Rating (Calculated Room Rating)
Marketed Room Rating (Calculated Room Rating)
800 sq ft (380 sq ft)
1300 sq ft (540 sq ft)
1300 sq ft (700 sq ft)
800 sq ft (190 sq ft)
H13 HEPA with optional upgrades
H13 HEPA with optional upgrades
5 stage HEPA 
Energy Use
Energy Use
36 watts on high
25 watts on high
55 watts on high
57 watts on high
Best Feature
Best Feature
Real-time air quality monitor with wifi connectivity
Real-time air quality monitor with wifi connectivity
Low profile and lightweight

The Bottom Line

The Alen 45i air purifier is a great option for homeowners looking to purify medium size spaces up to 400 square feet. Its high-performance filter and low energy use mean lower operating costs than competitors. And the highly useful auto-mode and real-time air quality monitor allow you to set it and forget it for cleaner home air without the work.

To learn more about the 45i or to purchase one for your home today, click here.

Do you have any questions relating to this article? Email us at [email protected] or call us on +1 (310) 961-4908

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Photo of author
Sara Seitz is a freelance writer and novelist. She lives with her husband and wildling toddler in Colorado where she spends her days working on their house, gardening, and reconnecting with nature.

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