Alen BreatheSmart 45i review

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 I 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 for both commercial and residential settings. Their most popular product line is the BreatheSmart range, which includes the Flex, 45i and 75i. 

The BreatheSmart 45i is the mid-size model in the BreatheSmart series, sitting between the 35i and 75i.

I picked mine up for £279.99 ($375.67) on eBay in 2023, but it sold on Alen.com and Amazon for around $428 when I published this review.

The lowdown on the Alen BreatheSmart 45i

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“So… is the Alen 45i good for you?

Considering only the initial price and top-speed CADR, it’s difficult to argue that the Alen 45i will ever be a top budget pick.

However, the Alen 45i does have some interesting benefits that could make it worth the extra price.

It has the same quiet fan speed performance as some of the best mid-sized air purifiers and fairly low energy usage, which means running costs are also on par with some of the best models out there.”

—Danny Ashton, Founder & Senior Writer

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If you don’t want to watch my full review of the Alen Breathsmart 45i, here are the 4 things I like and the 2 things I don’t

The BreatheSmart 45i currently retails for $419.00. It has a CADR test report on the EnergyStar Website, and the device was certified in 2018.

For this dust CADR score of 207.9 cfm, we would expect it to clean the HouseFresh test room of all PM1 particles in a similar time to the Dyson Big and Quiet BP06, which managed to clean our test room in 30 minutes.

We will also examine its effectiveness at lower fan speeds, as sadly, CADR only tests at top speed.

This device has 0 ppb of ozone, which suggests it uses a low-power ionization process. According to Alen, it releases only 0.001 ppm. In comparison, the background level in the United States is 0.015 and 0.045 ppm. I do appreciate that Alen allows you to disable the ionizer for those who might have a sensitivity. When disabled, it will mean zero ozone, and I appreciate that it’s easy to do via a button on the control panel.

Want to watch a video version of this review?

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.

Before we jump into the design, the Alen 45i was released in November 2019, so it is 6 years old at this point.

The reason I share this historical tidbit is that many air purifiers look mightily similar to the Alen 45i.

Like we have seen with Levoit’s popular models, I believe the Alen 45i has been a big inspiration for other air purifier designers over the years.

It uses a front cover that can be changed to 5 colors/textures for an extra cost. 

The rectangular design’s benefit is that the filter can be easily accessed. The cover is held shut by magnets.

There is a solid handle underneath the control panel at the back. 

From left to right, you get an ionizer button,then a  filter light that shows green, yellow and red, and a light button for low, high, and off.

The on/off button is in the middle, and it includes a light that adjusts color depending on the level of air quality detected by the sensor from Blue (low) to Purple (very significant.) This is based on data from the sensor at the side of the device; The onboard sensor is a PMS7003—one of the more accurate laser sensors used in purifiers. It’s the same sensor tech in our lab testing setups.

Most sensors used for auto-modes in air purifiers are optical sensors, which are much cheaper. The benefit of laser sensors is that they react quickly to particle-level changes and don’t need continual cleaning, as you can see with cheaper optical sensors.

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.

Depending on your preference, You can switch on or off the unit’s ionizer function. This technology releases positive and negative charges into the air, which causes particles to lump together, making capturing the HEPA filter easier and also helping to slightly reduced VOC’s.

The downside is that this technology can create ozone as a byproduct. 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. However, unlike manufacturers such as Blueair, I’m glad they still gave users the choice to use or not to use.

Those looking for more technical features will be glad to hear that the 45i is compatible with the Alen Air app.

The unit I’m testing here was purchased as a UK version, so it doesn’t have app support. However, if you have an older 45i, you should still be able to use the app even if it wasn’t sold as having app support. Alen installed Wi-Fi functionality in many of the older 45is years before they rolled out the app, so if you do have an older 45i, be sure to try to connect to the new Alen app. 

I plan to when we test the latest Alen 35i later in the year, so I will be sure to update my thoughts on the web version of this review.

For the app, Apple had 2.6 out of 5, and Android had 3.2 out of 5. After reading the reviews, I noticed that there is no standout issue as of mid 2025, but some customers complain that it’s a very simple app. It looks like Alen has been upgrading the app, as it now has historical data from the sensor and the ability to schedule when it comes on and off.

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.

One unique feature of the Alen range of air purifiers is that you can choose your filter when you buy from them directly. 

The Pure uses only a medical-grade HEPA filter and no gas carbon element. For $15 more, you can get the Fresh filter, including 0.66 lbs of pelleted carbon.

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.

The odor filter, which includes a carbon pellet and a specific catalyst to more effectively neutralize specific gases that cause odors, costs $30. 

For $50, you can choose the VOC/Smoke filters with the most pelletized carbon, which gives you 2.38 lbs of activated carbon.

We can compare these carbon amounts to other air purifier models:

Air Purifier Model	Carbon Amount
Winix 5500-2	226g
Levoit Core 400S (Basic Filter)	240±10g
Levoit Vital 400S (Smoke Filter)	450g
Alen 45i Fresh Filter	299g
Alen 45i VOC/Smoke Filter	1079g
Dyson Big+Quiet BP06	900g

The Alen VOC/Smoke filter has much more carbon than what we generally see from other air purifier brands, with even more than the much larger and pricier Dyson BP06.

This filter choice at the point of purchase allows you to customize it to your specific needs.

Another highlight of Alen is that they have a lifetime warranty if you have an active filter subscription or can prove that you only used OEM filters for your device.

The pre-filter used is a black mesh layer connected with Velcro, which Alen recommends keeping in place for cleaning with a vacuum. However, I still prefer having a separate pre-filter that can be removed for cleaning, making life a little easier.

One final thing about Alen and filters is that I have a 2010 Alen model, the Alen A350. I was pleased to see that even though it’s been 15 years, you can still buy new filters directly from Alen! While the A350 is much more energy-hungry than modern devices, it can still clean the air well.

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

The Alen BreatheSmart 45i cleared our test room in 30 minutes

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

According to our Zen sensor, the Alen 45i needed 30 minutes to achieve PM1 zero in our 728 cubic ft. test room. We estimate a PM1 CADR of 198 cfm, which matches up well with the AHAM DUST CADR result.

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 30 minutes for the Alen BreatheSmart 45i to clean the air in our test room:

Air cleaning speed test results compared

We can compare this to other similar performing devices running at their top speed:

	Time to PM1 Zero	List Price
Levoit Vital 200S	23 minutes	$189.99
Winix 5500-2	23 minutes	$249.99
IQAir Healthpro Plus	28 minutes	$999.99
Alen 45i	30 minutes	$429
Dyson BP06	30 minutes	$899.99
Core 400S [European]	30 minutes	$292.79

The table shows that for raw speed at top speed, the Vital 200S and Winix 5500-2 offer more CADR at a lower unit price.

I also made sure to test the Alen 45i without the ionizer, and it also managed to remove all PM1 in 30 minutes. The ionizer function might be helpful for gases and odors, but according to our tests, it doesn’t seem to improve particle removal performance.

Noise levels test results

Of course, performance means nothing if it’s too loud to use. Here’s how the 45i stacks up in our noise tests.

If an air purifier is too loud, you will turn it off eventually.

When recording the decibel levels created by the 45i from 3ft away, we got the following results:

This compares well with other devices we have tested:

I also made a comparison with other devices that have similar performance:

	Time to PM1 Zero	Sound level at top speed
Levoit Vital 200S	23 minutes	57.7 dBA
Winix 5500-2	23 minutes	58.9 dBA
IQAir Healthpro Plus	28 minutes	61.2 dBA
Core 400S [European]	30 minutes	55.9 dBA
Alen 45i	30 minutes	56.1 dBA
Dyson BP06	30 minutes	51.4 dBA

The Alen 45i is the fourth quietest on our list, but it is still 5 decibels higher than the Dyson BP06.

At speed two it hits 42.2dBA, which is below the 45dBA limit we use for our quiet test, and when we tested it again in our test room, is cleared all PM1 in 48 minutes, which we estimate a CADR of 123 cfm

We can compare these results with other air purifiers running at sub-45dBA:

	Time to PM1 Zero	Sound level at top speed
CleanAirKits Luggable XL	23 minutes	38.8 dBA
Winix 5500-2 [speed 2]	43 minutes	41.5 dBA
Levoit Vital 200S [Speed 2]	46 minutes	41.9 dBA
Dyson BP06 [Speed 1]	46 minutes	40.4 dBA
Alen 45i [Speed 2]	48 minutes	42.2 dBA
Core 400S [European]	50 minutes	44.4 dBA
IQAir Healthpro Plus [Speed 3]	68 minutes	40.9 dBA

When accounting for lower sound usage, the Alen 45i is on par with the best-performing midsize air purifiers.

But as with many HEPA retail devices, it just can’t compete at low sound levels with devices like the Luggable XL, which use PC fans.

I also tested PM removal performance for the Alen 45i at Speed 3.

At Speed 3 it hit 51.1 dBA and cleaned our test room of PM1 in 36 minutes with an estimated PM1 CADR of 165 cfm.

You can see the results for all the different fan speeds here: 

	Sound levels at 3ft away	Time to PM1 zero	HouseFresh CADR estimate
Alen 45i Speed 1	36.2 dBA	144 minutes	38 cfm
Alen 45i Speed 2	42.2 dBA	48 minutes	122 cfm
Alen 45i Speed 3	51.1 dBA	36 minutes	165 cfm
Alen 45i Speed 4	56.1 dBA	30 minutes	198 cfm

Alen claims it uses ‘pink noise,’ which should sound smoother than regular white noise, especially when sleeping. But does it really sound better? I used a calibrated mic and audio analyzer to find out.”

Using the spectrometer, I wasn’t able to differentiate between the other models, but to my ears, the Alen 45i did have a smoother fan sound than the Winix 5500-2, which seemed to oscillate a little at lower fan speeds and top speed.

But have a listen for yourself:

The cost to run an Alen BreatheSmart 45i: $136.64

1. Electricity costs = $43.32 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. 

We used our energy meter to record how much energy the Alen 45i  uses when running at each fan speed and with and without its ionizer, and also while on standby.

	Energy in Watts WITH IONIZER	Energy in Watts without Ionizer
Standby	0.8 watts	0.8 watts
1	5.1 watts	4.4 watts
2	10.1  watts	9.3 watts
3	22.8 watts	22.3 watts
4 Top Speed	38.7 watts	38.5 watts

This compares well with other devices with similar air cleaning power levels, especially when looking at the amount of energy used.

	Time to PM1 Zero	Yearly energy usage at top speed
CleanAirKits Luggable XL	23 minutes	$11.66
Levoit Vital 200S	23 minutes	$49.48
Winix 5500-2	23 minutes	$59.38
IQAir Healthpro Plus	28 minutes	$152.83
Alen 45i	30 minutes	$43.32
Core 400S [European]	30 minutes	$44.03
Dyson BP06	30 minutes	$36.66

2. Filter costs = $93.32 per year

Energy costs are not the only costs that add to an air purifier’s running cost; eventually, you will need to replace the filters.

Alen says you need to replace the filters for the 45i between 9 and 12 months, and as always, we will use the lowest estimate.

The recommended OEM Pure Filters cost: $69.99

This means the total filter costs for 1 year for the Alen 45i are $93.32

We can combine that with energy costs and compare it with other similar performing air purifiers:

	Annual Energy Cost	Annual Filter Cost	Total Annual Running Cost
CleanAirKits Luggable XL-7	$11.66	$43.64	$55.30
Levoit Vital 200S	$49.48	$49.99	$99.47
Alen 45i	$43.32	$93.32	$136.64
Coway Airmega 200M	$85.56	$39.98	$125.54
Winix 5500-2	$59.38	$79.99	$139.37
Levoit Core 400S [Europe]	$43.32	$99.98	$144.01
Dyson BP06	$36.66	$157.98	$194.64
IQAir Healthpro Plus	$152.83	$244.53	$397.36

With OEM filters, the Alen is more affordable than the Dyson BP06, IQAir Healthpro Plus, and Winix 5500-2. However, it is more expensive than the Levoit Vital 200S, Coway Airmega 200M, and, as expected, the Luggable XL-2 from Clean Air Kits.

Be aware that these costs are based on the standard Pure filter that contains no carbon. I expect this particle-only filter to last at least 12 months in the average home environment.

Generic filters are available, and we had a chance to test the Pureburg version of the B4-Fresh, which does contain some carbon and paid £29.30 or ($39) for one filter and 4 pre-filters.

When testing top speed performance with the Pureburg filters, it took 40 minutes to achieve PM1 Zero. We know that using carbon with a particle filter will reduce the top speed CADR, but we don’t know the total amount of carbon that Pureburg uses in this filter.

For most people, I recommend sticking with the OEM filters as Alen backs them, and it will also mean you keep the lifetime warranty. If you can, I would choose the subscription for 1 filter every 12 months, as you will also save 10% compared to buying when you need them.

So… is the Alen 45i good for you?

Considering only the initial price and top-speed CADR, it’s difficult to argue that the Alen 45i will ever be a top budget pick.

However, the Alen 45i does have some interesting benefits that could make it worth the extra price.

It has the same quiet fan speed performance as some of the best mid-sized air purifiers and fairly low energy usage, which means running costs are also on par with some of the best models.

The noise itself is also worth talking about.

Many good-performing devices sometimes have strange whirring, especially when running on lower sound levels.

To my hearing, the Alen 45i has a more stable fan speed, which might be preferable to some people.

Another big plus for Alen is that they have been manufacturing air purifiers for over 20 years and are still providing filter support for their older models today. A big worry is that you buy a great-performing device that loses filter support in just a few years, and I don’t have this worry with Alen.

Their lifetime warranty is also unique, but be aware that you must register and then use OEM filters via the subscription, or be able to prove that you have only used Alen filters on your device.

If you are looking for a more premium model and care about the type of sound produced, then the Alen 45i is well worth your consideration for rooms up to 300 square feet. Those with bigger spaces will need to upgrade to the Alen Breathsmart 75i with its dust CADR 351 cfm and I am looking to review the latest 75i very soon.