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How do we know that Alen air purifiers can capture virus particles including COVID-19?

Rigorous testing.

At Alen, we specialize in making shared spaces safer and healthier. As parents, we also believe in the essential value of in-person learning. But before we prioritized supply to schools and universities (even going out of stock to consumers)— and before a single Alen air purifier entered one of the 50,000 classrooms we now protect—we invested in state-of-the-art testing.

In July of 2020, Alen contracted Minnesota’s LMS Technologies, one of the nation's top air media and filter testing labs, to ensure our True HEPA purifiers could capture virus particles rapidly and effectively.


Test Results: Alen True HEPA Air Purifiers Capture COVID-19

According to independent microbiology tests, the Alen BreatheSmart 75i:

  • Removed over 99% of virus particles from a 1,050 CuFt test chamber within 20 minutes
  • Captured over 99% of particles in the COVID-19 particle size range (0.06-0.14 microns)

Test results show rapid and effective virus capture

“Any True HEPA H13 filter in such a chamber will eventually clear it depending on its CADR (clean air delivery rate) airflow,” said Alen CEO, Andy Graham. “Alen purifiers are unique in the efficiency (time) in which we clear the chamber.”

The bioaerosol tests used a live FDA-approved COVID-19 proxy virus (MS-2 bacteriophage), a living virus particle very similar in size to coronavirus. Testing was conducted at the LMS facility in Bloomington, Minnesota using in a sealed stainless-steel chamber.

Realistic Test Conditions: A room-sized chamber


Alen is one of very few brands to test its actual units and filters in a room-size test chamber. The 1,050 CuFt chamber used by LMS is roughly the size of an office or meeting room—recreating real world conditions.

This context is important because we know that "viruses in aerosols can remain suspended in air for many seconds to hours," as well as "travel more than two meters," according to the open letter from 239 scientists that changed the World Health Organization's stance on airborne spread.  

How Big are Viruses?

Our stringent testing didn't just consider a real room size. We also took into account actual size of COVID-19 particles.

When exhaled, virus particles initially attach to larger respiratory particles. But those respiratory particles eventually evaporate, leaving microscopic virus particles to float and concentrate in the air. But how small are they?

Virus particles are extremely small. According to a study published in the New England Journal of Medicine, COVID-19 particles range between .06 microns and .14 microns. That’s over a thousand times smaller than a human hair. The LMS study found that Alen captures over 99% of virus particles throughout that range. 


 A size chart showing sizes of common airborne particles

Sizes of various common airborne contaminant particles

Why Airflow Matters as Much as Virus Filtration

To effectively protect any space—classrooms, offices, restaurants, or homes—capturing particles in the COVID-19 size range is just the first step. Experts say the key to combating COVID-19 is airflow. In other words: ventilation and filtration. HEPA filtration is only as good a purifier’s ability to exchange a room’s full volume of air. For example, Harvard Health recommends 4-6 air exchanges per hour. 


An illustration of virus particle concentration in a room with and without an air purifier

A classroom with and without added ventilation and an air purifier (Credit: NY Times)

COVID-19 transmission is like second-hand smoke—concentrated and prolonged exposure is the danger. Air purifiers with the proper airflow capacity for a room help to keep virus particle counts low, so an infected person is not adding enough particles to infect others.

By achieving over 99% effectiveness clearing a virus-saturated chamber roughly the size of an office or meeting room within 20 minutes, the study demonstrates that Alen purifiers can successfully keep virus concentrations low in real world settings.

Why We Dialed It Down: Quietness is Crucial 

It’s important to note that these tests were conducted at speed four of five. Why? Sound levels. In other words, we wanted to ensure both effectiveness and quietness.


At top speed the BreatheSmart 75i is quieter than the sound of rain and a teacher's normal speaking voice

Protecting school classrooms was our top priority in this testing. But effective air cleaning that creates excessive noise is useless in a learning environment. In considering school air purifiers, learning loss due to distractions is a huge factor for educators. According to the American Academy of Audiology, noise above 70 decibels is considered loud and can disturb learning.

Students in a classroom with an Alen HEPA air purifierAn Alen air purifier at work in Austin’s Redeemer School

The Alen BreatheSmart 75i is already the quietest HEPA air purifier by capacity on the market. It’s our top recommendation for classrooms. At top speed, it emits only 49 decibels, which is quieter than a typical conversation. For these tests, we wanted to validate its COVID-19 capture efficacy at an even quieter speed. At the test speed (four), it emits only 47 decibels.

Alen BreatheSmart 75i True HEPA Air Purifier From $749

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“For me, my staff, and parents, air purifiers add another layer of protection and peace of mind,” said Amber Schraeder, Education Director of Redeemer Lutheran School. “We know we’re doing every single thing we can to create a normal, in-person learning experience, which is so critical.”

For more information about how Alen's Clean Air Experts can help you protect any learning environment, visit our Alen for Schools page, call 855.200.5483, or email our dedicated EduSafety team edusafety@alen.com

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