Alen BreatheSmart FLEX Review

Modern yet classic design, Alen BreatheSmart FLEX HEPA air purifier is slotted below Classic and Fit50 without sacrificing all the essential purifying goodness. Nicely balanced between airflow distribution and purifying applicable area, comparing each feature and pro/ con, what is unique about the air purifier that could offer itself ahead of its contenders? Head over to our full review and see the differences between other BreathSmart models.
± 349.00 p
     Annual filter ^    
± 39 - 118 p
 Online price*
** MRSP (Manufacturer's Suggested Retail Price)/ RSP (Retail selling price) is provided by cleanairprice.com. Accurate at the time of posting.
^ Annual filter cost is calculated based on filter price and 12 hours of usage. Pricing could vary depending on air quality, usage frequency, and speed.

Alen BreatheSmart FLEX Specification

ProductAlen BreatheSmart FLEX
15 x 25 x 8.5 in
(38.1 x 63.5 x 21.6 cm)
Weight15 lb (6.8 kg)
Coverage (up to)700 sq. ft. (65 m2)
Airflow speed53-187 cfm (90-318 m3/h)
Dust free (CADR)245 cfm (416 m3/h)
Pollen free (CADR)245 cfm (416 m3/h)
Smoke free (CADR)245 cfm (416 m3/h)
Humidifying(H) speed
- Lifespan
- Replacement cost ($)
Washable Pre-filter (with HEPA filter)
6 - 18 months
HEPA filter
- Lifespan
- Replacement cost ($)
HEPA-Pure Filter FL40
6 - 18 months
+- 59
Carbon filter
- Lifespan
- Replacement cost ($)
Ionizer/ Technologies
UV-light/ PCO
Other filter
All-in-one filter
- Lifespan
- Replacement cost ($)
Optional/ Addon
6 - 18 months+- $79
HEPA-OdorCell Filter FL40-MP
6 - 18 months+- $89
HEPA-Fresh Filter FL40-CARBON
6 - 18 months+- $69
Noise level39 - 55 dB
Power usage level36 W
Timer/ Scheduler2, 4, 12 hours
Auto mode
Air qualityAQ indicator
Filter change indicator
More color options
Wi-Fi/ BTBluetooth
Remote control
Child lock
WarrantyLifetime Limited Warranty
Email/ Phone support

Key features

  • 2-stage filtration (3-stage with optional filter upgrade)
  • Washable Pre-filter/ HEPA-Pure filter
  • 4 fan speeds
  • Personalizable front cover
  • Child-lock control panel and child-safe vent guard
  • 4, 8, 12 hour timer
  • Lifetime limited warranty
  • [Optional] filters - HEPA-Silver filter, HEPA-FreshPlus filter, HEPA-OdorCell filter


  • Changable front panel with tons of modern wood trim design.
  • Consistent and strong airflow delivery rate that supports the wide purifying area.
  • Up to 3 optional filter upgrade that is excellent against allergens and odors.
  • Longer lasting filters compare with similar segment models although that would also depend on usage frequency.
  • Built-in timer (2, 4, 12 hours).
  • Child friendly machine with locking control panel and safe vent guard.
  • Lifetime Limited Warranty.


  • Lacks odor filtration on bundled HEPA-Pure filter (Need to move up with one of the optional filter).
  • No dedicated odor carbon filter that separates from the HEPA filter that would reduce each filter workload.
  • Noisy at highest fanspeed although not the worst in its class.
  • Lacks advanced filter replacement indicator (only basic version), SmartSensor (thus Auto mode), Ionizer. All these is available in BreathSmart/ FIT50.

The starters

Alen BreatheSmart FLEX dimension
15 x 25 x 8.5 in
(38.1 x 63.5 x 21.6 cm)
Alen BreatheSmart FLEX weight
15 lb (6.8 kg)

The shrunk version of Classic BreatheSmart model, Alen BreatheSmart FLEX is a well-designed air purifier that comes with a smaller dimension at 15 x 25 x 8.5 in. Weight wise is 15 lb thus lighter by least 6 lb than the original, fitting quality remain unchange with zero air bypass. What’s also remain is the swappable/ changeable front cover panel where you could choose one of the ideal wood trim design to suit your home decor. Underneath the front panel you will find air inlet located at side and bottom while air outlet is located behind at top. A carrying handle is also at the back right beneath the outlet.

Alen BreatheSmart Flex Control

Shifting our attention to the top control panel, there are 6 clearly labelled round buttons and dedicated indicator lights above each button. Unlike the previous version, the HEPA air purifier has a capacitive touch panel which means each button would only require a light touch and a chime can be heard to reassure your action. To turn on the air purifier, press the middle Power button. Press again to turn off all indicator lights and again to turn off the air purifier. At this point you can start adjusting the air purifier fan speed. Press the Speed button repeatedly to loop between Speed 1, 2, 3, T (turbo). The indicator above will show you what speed you are currently in. Same goes with the Timer button that press repeatedly will cycle between 2, 4, 12 hours. Moving to the left, Filter life button allows you to reset the filter countdown timer by pressing and holding the button for 5 seconds. Do this after you have successfully changed to a new filter when the indicator light turns gradually from Green, Yellow to Red (traffic light style). Finally, you can lock the control from any modification or fiddling from your kids by pressing and holding the Lock button for 3 seconds. The 2 buttons missing out from BreatheSmart Classic and Fit50 series is the Auto and Ion button, both features are sadly omitted here.

Other common sets of features include your pre-selected HEPA filter, 4 fan speed, air quality display, basic filter replacement indicator, Child lock/ Auto-off safety feature that activates when front cover is not tightly closed, UL listed, ENERGY STAR rated and Alen’s unique Lifetime limited warranty.

Airflow, speed, and CADR

Alen BreatheSmart FLEX coverage
Purifying coverage
700 sq. ft. (65 m2)
Alen BreatheSmart FLEX fanspeed
With a smaller overall size, Alen BreatheSmart FLEX HEPA air purifier has a reduced purifying coverage that by no means is poor as it stands at 700 sq. ft. Ideal for most room sizes including bedroom, kitchen, basement and typical household living hall. Airflow delivery rate also drops when compare to BreatheSmart Classic especially on lower speed; expect speed 1 at 53 cfm, speed 2 at 135 cfm, speed 3 at 147 cfm and turbo at 187 cfm. Another trade-off is the lack of Auto mode within the 4 selectable speed.
Alen BreatheSmart FLEX dust CADR
245 cfm (416 m3/h)
Alen BreatheSmart FLEX pollen CADR
Pollen CADR
245 cfm (416 m3/h)
Alen BreatheSmart FLEX smoke CADR
Smoke CADR
245 cfm (416 m3/h)
Although not tested in the typical channel, Alen BreatheSmart FLEX HEPA air purifier dust, pollen and smoke CADR is equally impressive at an estimated 245 cfm overall. Regardless which or what types of air contaminants is presence, large particles e.g. dust to the smaller allergens like pollen/ mold would be completely capture by the air purifier. Smoke and odors related particles would fall into the air purifier checklist if the right type of filter is used i.e. HEPA-Fresh filter (optional addon purchase).

What’s inside count

Utilizing the same one filter kit setup, the initial velcro attached pre-filter above the HEPA filter is great at removing visible airborne particles while prolonging the HEPA filter lifespan. Moving on to the primary HEPA filter, you can select one of the 4 available HEPA filters that would trap smaller, micron-size particles with each having their unique specialty. The standard HEPA-Pure filter is cheap and effective against common household allergens but lacks any deodorization filtration. HEPA-Silver filter is very effective against mold, germ type bacteria. Our favorite HEPA-FreshPlus is great against asthma triggers chemical, VOCs and smoke, HEPA-OdorCell is best used to neutralize odors from diaper or pets. Regardless of which filter options you choose, all filter kit shares the same size and build quality as you would expect. The default Ionizer is also available in the air purifier.

Filter maintenance and care

Begin by unplugging Alen BreatheSmart FLEX HEPA air purifier to prevent electric short circuit. Then pull out the front panel starting from the 2 bottom sides of the cover. With the filtration exposed, continue removing the old filter by pulling the pull strings. Remove the plastic wrap from the new filter and place it with the pull strings facing outwards. Snap back the front panel via the top tabs and your air purifier is good to go. You can prolong the HEPA filter lifespan by washing the removable pre-filter attached to it. First, peel off the black layer foam held on with Velcro, then lightly vacuum or clean the pre-filter from any trapped particles. Stick it back to the HEPA filter once done. With only one filter needed to be change, you only need to spend 2 minutes of your time within 6 - 18 months period.

Keep it down

Alen BreatheSmart FLEX noise level
Noise level
39 - 55 dB
Alen BreatheSmart FLEX power consumption
Power consumption
36 W

Even without the WhisperMax technology incorporated, Alen BreatheSmart FLEX HEPA air purifier is comparatively more silent than the standard BreatheSmart version at only 39 - 55 dB noise level. On real life scenario, you can hardly tell apart between the 2. No problem running in bedroom however, the lack of Auto mode is a bit of let-down especially in night time where you could let the air purifier run at optimal speed rather than full blast.

Moving to power consumption, at an average of 36 W rate, power usage is low on this Energy Star unit and unlike the standard Classic version, you can clearly see the difference in your electricity bill in long-run. Again, the lack of Auto mode is a stumble block, but in this air case, not a big deal.

At what cost

Alen BreatheSmart FLEX MRSP/ RSP
+- 349.00
Alen BreatheSmart FLEX annual filter replacement cost
Annual Filter Cost
+- 39 - 118
^ Replacement filters/ estimated cost
Alen BreatheSmart FLEX HEPA air purifier is not dirt cheap, it is still the cheapest in BreatheSmart series but with few features you would need to compromise. Other than the weaker purifying performance, the lack of air quality indicator, sensor/ auto mode and basic filter replacement indicator is also noticeable. Annual filter replacement is the cheapest in its series although is just tad lower than standard BreatheSmart. Filter lifespan wise is the same between 12 - 18 months depending on usage frequency and surrounding air quality. You could easily purchase anyone of the replacement filters online as Alen still making the HEPA filters. Ignoring the price factor, Alen BreatheSmart Classic/ Fit50 seem like a better deal as both comes with Auto mode.
The cheapest in BreatheSmart series although not necessarily cheap, The base unit without any addon already cost more than Winix HR1000, Honeywell HPA300 or Coway AP-1512HH despite the price chart not painting the full picture. Annual filter replacement is typical Alen BreatheSmart fashion that could be one of least costly on limited use to relative expensive on non-stop operation. We use the default HEPA-Pure filter as a comparison guide in chart however, you should expect more or less the same result even with different selected filter. So on to buying Alen BreatheSmart Flex, Beside the physical store like Lowe's, Home Depot, Target where you can get a hold on the HEPA air purifier, we recommend buying straight from Amazon as it is convenience, 30 days money back guarantee, free shipping (selective location) and comes in cheaper bundled deal. Another worthy place to consider is Alen's official website that offer wider selection on front panel design, 60 days money back guarantee, free shipping to U.S. continent and also bundled/ family pack deal.

Alen BreatheSmart FLEX VS the challengers

Alen BreatheSmart FIT50

Higher purifying coverage (up to 900 sq. ft.) with SmartSensor and Auto mode. Downside is the higher price tag and lower CADR output which is a surprise to many. Alen BreatheSmart Fit50 also might be on end of its life cycle so expected limited stock availability.

Alen BreatheSmart Classic

Standard version with highest price tag but comes with the best purifying coverage, airflow performance and full-set of features including the sorely missed SmartSensor for Auto mode. Being the longest running model in BreatheSmart lineup, Alen BreatheSmart Classic is also the air purifier that holds the best possible online deal.
Rabbit Air MinusA2 SPA-700A

Rabbit Air MinusA2 SPA-700A

If you do not mind topping up a little bit more cash, Rabbit MinusA2 has more filtration depth than flex (6-stage VS 3-stage) and a more adaptable frame body that you can hang just about anywhere. Otherwise, both air purifiers have the same customizable filters and front panel design to choose from.
Airmega 300

Airmega 300

As both air purifiers offer identical set of features and sensors, Airmega 300 is distinctive in its design, airflow distribution and purifying coverage but comes at a higher cost. You also have to give up the option to customize your main filter and front panel design.

Final thoughts on Alen BreatheSmart FLEX

Bring to a conclusion, Alen BreatheSmart FLEX HEPA air purifier is a remarkable with decent airflow delivery rate. 87% of 4 – 5 stars Amazon users think this is the best air purifier in its class to cover against household contaminants and allergies. The option to choose the right type of filters based on their needs is a big plus. People also like how fast and effective it can purify their indoor air. On the opposite spectrum, the small 13% that gave it 1 -3 stars does not feel this is a justifiable purchase or simply think the air purifier does not work at all. There are also complains on the customer service but that is a few rare cases. Comparing the all-round advantages/disadvantages, you can most definitely see there are more strong points on the air purifier than the negative points.
Alen BreatheSmart FLEX

Max Fernandez

A loving father and a dedicated reviewer for airfuji.com with more than 1000 air purifiers under his belt. Max Fernandez is also one of the million patients currently suffering from asthma. Feel free to nudge him if you have any questions.

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