Put the FLEX to work cleaning up to 700 square feet of air every 30 minutes. Add a customizable filter for your specific needs in each space, alen breathesmart and you’ve got pure air, everywhere. We’ve calculated this using the B4-Fresh filter, which we recommend for most household pollutants.
This unbeatable combination allows for whisper quiet removal of particulate matter, even on the highest setting, 24/7. The biggest difference between the features on the 45i and Flex is that the 45i comes with an auto mode. This uses the same air quality information from its sensor to adjunct the fan to suit the amount of pollutants in the air. The cost of replacement filters is the true cost of any air purifier. Some companies do have a ridiculously low price of the air purifier itself because they earn money on the replacement filters. This indicates at what fan speed setting you should run the Classic large air purifier.
Predicted brand reliability ratings are based on estimated problem rates for newly purchased room air purifiers, by the end of the 5th year of ownership. The app is designed to manage mulitple purifiers but lets you control and drill into data from individual units. To recap our previous review, the 75i is a True HEPA Air Purifier designed for residential or commercial use. The latter seems a more likely scenario given the appliance’s 27 x 19 x 12-inch (HxWxD) measurements and its ability to service rooms up to 1,300 square feet. A pair of wheels on the rear make moving the 27-pound unit slightly less cumbersome.
On Auto mode, a built-in dirt sensor or other inputs will allow the fan to run on a higher fan speed when the air is determined to be dirty and on a lower speed when clean. That means your Alen air purifier is guaranteed for life with a convenient filter subscription. If you ever have issues with your purifier, we’ll fix it or replace it for FREE. This review is part of TechHive’s in-depth coverage of the best air purifiers. HEPA filters trap airborne pollutants in their tightly woven maze of fibers (think of a fly in a spider’s web), removing them from the air.
The technology inside these two units may differ, but looking at them side-by-side, you’ll see they are practically exactly the same. When it comes to specifications, the 45i is the winner as it’s lighter, quieter and, due to its higher CADR, tackles pollutants in larger rooms than the Flex. In 2024, however, the Classic model is far surpassed by the superior Alen BreatheSmart 75i model; the best-of-the-best air purifier in general, not only among Alen Air purifiers. This is quite a lot; comparatively, as we have discussed in the Alen BreatheSmart 75i review, that air purifier generates only 25 dB at Speed 1.
It was a close call between the 45i and the Flex regarding design, filters and the numbers, with only one minute to separate them in our cleaning performance tests. The difference comes with the features included and the annual running costs. When you compare these two to some of the other air purifiers we’ve reviewed of similar size, you’ll see they are a little louder.
Alen shows they mean business by only including heavy-duty, thick H13 (medical grade) HEPA filters with activated carbon pellets in their units. The 45i boasts a higher CADR at 245 CFM whilst the Flex falls slightly behind at 225 CFM. But, lasko pedestal fans when we put these two units through our performance tests, that extra 20 CFM only translated to one-minute difference to clean the contaminants from our room. When we compare two units side-by-side, we first look at their cleaning power.