Alen Breathesmart 75i vs. 45i vs. 35i: Which to Buy?
Clean water, air, lights, and food are four of the most important environmental factors affecting your health. When it comes to air quality, many people assume the outdoors is the biggest concern, but according to the EPA, indoor air can be up to five times more polluted than outdoor air, trapping allergens, mold spores, volatile organic compounds (VOCs), and other pollutants inside your home. This is why we have multiple air purifiers running in our home most days of the year.
It started when we lived in the city, where pollution and traffic emissions were a constant concern, but even now in the burbs, I still prioritize clean air due to indoor contaminants like dust, pet dander, and off-gassing from furniture. After researching and testing multiple brands, I chose Alen as our sole air purifier because of its high efficiency, quiet operation, and medical-grade HEPA filtration.
We use the Alen BreatheSmart 75i, 45i, and 35i nearly every day, and today, I’ll break down why we rely on each model, the key differences, and how to choose the best one for your home based on your specific needs.
Alen BreatheSmart 75i vs. 45i vs. 35i: Comprehensive Air Purifier Comparison
Design & Aesthetics
BreatheSmart 75i: Features a sleek, modern design with customizable front panels in various colors to match your decor. Its substantial size, measuring 27" H x 18.5" W x 11.5" D, is good for larger spaces.
BreatheSmart 45i: Offers a compact and stylish appearance with interchangeable front panels. Its dimensions (25" H x 15" W x 8.5" D) make it ideal for medium-sized rooms.
BreatheSmart 35i: Designed for smaller spaces, it maintains the sleek aesthetic of the series while being more compact and lightweight for easy placement.
Performance & Coverage
BreatheSmart 75i: Designed for large rooms up to 1,300 sq. ft., it delivers a Clean Air Delivery Rate (CADR) of 350 CFM for smoke, 300 CFM for pollen, and 250 CFM for dust.
BreatheSmart 45i: Covers medium to large rooms up to 800 sq. ft., with a CADR of 245 CFM.
BreatheSmart 35i: Suited for small to medium rooms, it effectively purifies air in spaces up to 500 sq. ft., with a CADR of 190 CFM.
Filtration System
All three models use Alen’s True HEPA filters, capturing 99.97% of airborne particles down to 0.3 microns, including dust, pollen, pet dander, and smoke. Each also contains activated carbon to reduce odors and VOCs from household chemicals, pets, and cooking. Filters last 6-12 months, depending on use. To extend the lifespan, vacuum the pre-filter monthly and run on Auto Mode for efficiency.
HEPA Filter Options:
HEPA-Pure: Standard filter for dust and allergens.
HEPA-Fresh: Adds light carbon for mild odors and VOCs.
HEPA-Silver: Antimicrobial layer for mold, bacteria, and viruses.
HEPA-Odor/Heavy Smoke: Maximum carbon for strong odors, smoke, and chemicals. (We use this one.)
Noise Levels
Here's a comparison of the noise levels for the Alen BreatheSmart air purifiers:
BreatheSmart 75i: Operates at 25 dB on the lowest setting and up to 49 dB on the highest setting.
BreatheSmart 45i: Operates at 23 dB on the lowest setting and up to 49 dB on the highest setting.
BreatheSmart 35i: Operates between 24 dB and 42 dB, depending on the fan speed.
These noise levels are comparable to the ambient sounds of rustling leaves or a quiet library. It’s definitely some noise, but we come to find it as a consistent, calming hum in the background. You can also vary the speed manually, so keep it on lower settings.
Energy Efficiency
All models are Energy Star certified, ensuring efficient energy consumption. The 45i, in particular, is noted for its low energy usage, even when operating continuously at higher settings.
Smart Features
BreatheSmart 75i: Equipped with Wi-Fi connectivity, it allows control via the Alen Air app (ee pic below), providing real-time air quality monitoring and remote operation.
BreatheSmart 45i: Offers basic smart features, including an auto mode that adjusts fan speed based on air quality and compatibility with the Alen Air app for remote monitoring.
BreatheSmart 35i: Provides essential features suitable for smaller spaces, focusing on simplicity and ease of use.
Our Alen Breathesmart 45i, 75i, and 35i. Don’t mind the stickers the kids put on.
Price-to-Value Ratio: Cost Compared to Space Covered
BreatheSmart 75i:
Price: $749
Coverage Area: 1,300 sq. ft.
Price per sq. ft.: $0.58
BreatheSmart 45i:
Price: $429
Coverage Area: 800 sq. ft.
Price per sq. ft.: $0.54
BreatheSmart 35i:
Price: $215
Coverage Area: 700 sq. ft.
Price per sq. ft.: $0.31
My Experience
We’ve been using Alen Breathesmart air purifiers for years, and I can confidently say they’re one of the best investments we’ve made for air quality in our home. We have a 75i on the first floor, a 45i on the second floor, and the 35i is for the bedrooms—each strategically placed for their designated coverage maximum.
Alen app
What stands out most is how sensitive the air quality sensors are. Even though the indicator lights are usually off (just press the power button twice to turn them off), when they’re on, you can actually watch the air quality change in real time. It’s wild to see the color shift when I cook in the kitchen, when the cats use their litter pan, or even when my wife does her hair. The purifier instantly detects and reacts to changes in air quality, which is both reassuring and fascinating.
Another huge plus is the ability to disable Bluetooth, making EMF exposure a non-factor—a feature that’s hard to find in many smart air purifiers. While the app is nice (picture on the right), I used it once and then deleted it and disabled the Bluetooth (how to do that in here) like I do for most things due to the risk with EMF exposure. The kid safety screen is another thoughtful touch, preventing little fingers from getting into the fan outlet, which is great if you have young kids.
Beyond filtration, the Alen purifiers double as excellent white noise machines in the bedroom. Turn the 35i on high and it has the perfect background hum to block out noise while ensuring clean air while we sleep.
That said, they aren’t cheap, but they’re incredibly durable and built to last. At first, I thought I’d have to replace the filters every few months, but they’ve proven to be much longer-lasting than expected. Now, we just stock up on filters in bulk during Black Friday, which helps save money in the long run.
Overall, these purifiers check every box—high-performance filtration with a HEPA filter, quiet operation, real-time air quality monitoring, and user-friendly safety features. I can’t recommend them enough.
Takeaway
The “best one” comes down to what you’re looking for. Here’s the right one for you based on your priorities.
Best Price-to-Value Ratio: The BreatheSmart 35i offers the most affordable option with the lowest price per square foot, making it ideal for those with smaller rooms who want to maximize their value.
Best Overall Coverage: The BreatheSmart 75i covers the largest area and is perfect for large spaces, though it comes at a higher cost. It still provides good value for those needing comprehensive coverage.
Balanced Option: The BreatheSmart 45i offers a good middle ground for medium-sized spaces, with a slightly lower price per square foot than the 75i and greater coverage than the 35i.
Find them all here on Alen’s website:
FAQ
Q: Does the Alen Breathesmart automatically adjust fan speed based on air quality?
Yes, all three models feature Auto Mode, which adjusts the fan speed based on real-time air quality readings detected by the built-in sensor. This ensures optimal filtration without unnecessary energy use.
Q: How do I clean and maintain my Alen air purifier?
For best performance, wipe down the exterior and air vents monthly with a dry or damp cloth. The air quality sensor should be cleaned every few months using a soft brush or canned air to remove dust buildup.
Q: Can the Alen air purifiers remove VOCs (volatile organic compounds)?
Yes, Alen’s HEPA filters contain activated carbon, which helps reduce VOCs from household cleaners, paint fumes, and off-gassing furniture. If VOC reduction is a priority, consider Alen’s Fresh or Heavy Smoke filter options.
Q: Do Alen air purifiers help with wildfire smoke?
Yes! The True HEPA filtration system effectively removes fine particulate matter (PM2.5) from wildfire smoke, making it a great option for homes in areas prone to wildfires.
Q: Can I leave the Alen air purifier on 24/7?
Yes, these purifiers are designed for continuous operation, and running them 24/7 helps maintain cleaner indoor air. They are Energy Star certified, so they consume minimal electricity even on higher settings.
Q: Does the Alen Breathesmart work for pet allergies?
Yes! The HEPA filter captures pet dander, hair, and allergens, reducing symptoms for those allergic to cats, dogs, or other pets. The odor-reducing activated carbon also helps neutralize pet smells.
Q: Do Alen purifiers produce ozone?
No, Alen air purifiers do not produce ozone. They are CARB (California Air Resources Board) compliant, meaning they meet strict air quality safety standards.
Q: Can I use an Alen air purifier in my baby’s nursery?
Yes! Many parents use the 35i in nurseries because it doubles as a white noise machine while filtering airborne contaminants to create a cleaner sleeping environment for babies.
Q: Does Alen offer replacement warranties?
Yes, Alen offers a lifetime warranty on their purifiers as long as you are enrolled in their filter subscription program. Otherwise, there is a standard warranty that covers defects for a limited period.
Q: Can I control my Alen purifier with an app?
The 75i and 45i are compatible with the Alen Air app, allowing for remote control, scheduling, and real-time air quality monitoring. The 35i does not have app compatibility but still has Auto Mode.
Q: What’s the difference between Alen’s HEPA filter options?
Alen offers multiple filter types based on your needs:
HEPA-Pure: Standard filter for dust, allergens, and dander.
HEPA-Fresh: Includes carbon for light odor and chemical filtration.
HEPA-Silver: Antimicrobial filter for mold and bacteria.
HEPA-Odor/Heavy Smoke: Extra carbon layers for maximum odor removal, great for wildfire smoke or strong household odors.
Q: How loud are Alen air purifiers?
On the lowest setting, they’re virtually silent, and on the highest setting, they produce a low-level white noise (similar to a fan on medium speed). The 35i and 45i are quieter than the 75i, making them great for bedrooms.
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