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A Straightforward Look at the Complexities of Airborne Viruses & COVID-19

With the global outbreak of novel coronavirus (COVID-19) and the emergence of new variants, many are wondering whether air purifiers can provide protection against airborne viruses. Amid much confusion and misinformation, we want to clear the air and provide some useful facts about what air purifiers with True HEPA (H13) filters actually do to help remove viruses.  

Our greatest enemy right now is not the virus itself. It’s fear, rumors, and stigma. And our greatest assets are facts, reason, and solidarity,” said World Health Organization Director-General Dr. Tedros Adhanom Ghebreyesus.  

First and foremost, if you believe you or someone in your household might have COVID-19, take immediate action by following the Centers for Disease Control and Prevention (CDC) guidelines. And although coronavirus is at the forefront, it’s also important to note that these facts apply to all airborne viruses.

The Facts

Can HEPA purifiers capture viruses? Yes. An air purifier equipped with a True HEPA (high-efficiency particulate air)-rated filter can capture a portion of airborne virus-sized particles. Once trapped, viruses cannot multiply on their own or remain infectious for longBut NO air purifier can completely protect you from a virus.

"HEPA air purifiers are a passive, 'always-on' way to improve the overall health of a breathing space that doesn’t require major lifestyle changes," said Alen CEO, Andy Graham. 

 In this article, we’ll break down the following: 

  • How HEPA filtration technology works
  • Do HEPA filters remove viruses?
  • How viruses spread & why air purifiers can help
  • Why filtering airborne viruses is just one part of prevention
  • How air purifiers support immune system health + tips to stay well

An image of the first case of the novel Coronavirus (COVID-19).
An image of the first case of COVID-19, courtesy of the CDC.
Coronavirus’s name comes from tiny spikes that resemble a solar corona.


How HEPA Air Purifiers Really Work

Originally developed in support of cleanrooms for atomic energy development, the U.S. Department of Energy (DOE) created HEPA as a specification for suppliers of filtration products based on particle removal effectiveness, requiring them to remove 99.97% of particles 0.3 microns and above. (Alen True HEPA filters exceed that standard, removing 99.99% of particles down to 0.1 microns). Filters are commonly perceived as nets or a screen that will stop objects larger than the smallest holes while letting air through. That's a misconception. 


HEPA filters work much differently than how flies are trapped by a screen, as pictured. HEPA filters trap particles much differently than a simple screen or net.

Here’s the reality: HEPA filters are a complex weave of tiny fibers that carry an electrostatic charge which attracts bypassing particles—more like a magnet than a net. The smaller the fiber with the greater charge coefficient, the greater the likelihood of trapping ever smaller particles. All of this is effective to the extent that air can be channeled through enough filter material without air bypassing around it.

An extreme close-up of HEPA material. Note the irregular, maze-like weave. An extreme close-up of HEPA material, courtesy of Engineering360.


How Do HEPA Air Purifiers Protect Against COVID-19 and Other Viruses?

The most current state of the art in filter material is referred to as True HEPA by the DOE. True HEPA removes 99.97% of particles at 0.3 microns or higher, but this is a helpful yet incomplete description of HEPA capability. Particles below 0.3 microns (like the COVID19 and H1N1 flu viruses) will be captured by electrostatic attraction to HEPA material or when they become lodged in the HEPA filter’s maze-like fibers. While larger particles travel in a straight line, impacting and become trapped by HEPA fibers, nanoparticles bounce around in a random pattern (known as Brownian motion) which causes them to collide and stick to HEPA fibers.


A diagram showing the range of particulates a True HEPA filter can capture
A diagram showing the size range of airborne particles.

So how effective are HEPA filters at removing particles below 0.3 microns? Research suggests they are highly effective at doing so. In fact, a 2016 study by NASA found that “HEPA filters are nearly 100% efficient at capturing the spectrum of particles down to the very smallest airborne particles.”

While this sounds promising, the key takeaway is that no purifier brand should claim they can completely protect people from viruses including COVID-19. Air purifiers are an additive protective measure if properly sized to a room.

The only way to truthfully claim how effectively an air purifier can remove airborne COVID-19 particles is by conducting proxy tests in controlled environments, which we did.

The Research

In 3rd party independent testing, the Alen BreatheSmart 75i removed over 99% of virus particles from a 1,050 CuFt test chamber within 20 minutes.

These bioaerosol lab tests used an FDA-approved live COVID-19 proxy. Tests also showed over 99% removal throughout the entire COVID-19 particle size range (.06 - .120 microns).


Alen purifiers quickly and effectively remove COVID-19 particles, according to independent lab tests.


How Viruses Spread & Why Air Purifiers Can Help 

Viruses including COVID-19 spread in the air by close person-to-person contact, especially when an infected person coughs or sneezes, according to the CDC. Virus particles are attached to and carried by water vapor, which are tiny droplets that float in a fine mist. The length of time virus particles can survive in the air and on surfaces depends on a range of factors such as the type of virus and surface it lands on, but many can remain infectious for several hours.

According to an open letter to the World Health Organization from 239 international scientists, published in the journal Science:

“Viruses in aerosols can remain suspended in air for many seconds to hours, like smoke, and be inhaled. They are highly concentrated near an infected person, so they can infect people most easily in close proximity."

"But aerosols containing infectious virus can also travel more than [two meters] and accumulate in poorly ventilated indoor air, leading to superspreading events."

The only way to reliably remove virus sized particles from the air is by circulating the entire volume of air in a room or enclosed space multiple times per hour to increase the likelihood that nearly weightless virus particles will enter the airflow of a filter.  


To work effectively, a purifier must circulate air throughout your entire room.


Essentially, we live and breathe 'boxes' at home, work, restaurants, schools, and play spaces,” said Graham. “Any shared-air breathing space would benefit from a right-sized air purifier with a well-sealed, high capacity True HEPA air filter.”  

Why Filtering Airborne Viruses is Just One Part of Prevention 

Yes, we sell air purifiers and have for 15 years, but we will be the first to recommend additional means of wellness and immune system support in addition to breathing pure air. For example, transmission by physical contact can only be addressed by other non-airborne measures.  

COVID-19 can remain infectious for three hours when aerosolized into floating particles, according to another leading study. On surfaces, it remains viable for up to five days.

Likewise, “viruses can’t multiply on their own—they must infect the cells of a living creature,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Disease, told PBS.

What this means is that viruses trapped in an inorganic HEPA filter will stay there and die without further harmful effects. But since COVID-19 can live for up to three days on surfaces, it's critical that you follow ALL the CDC’s guidelines to prevent illness.

How Air Purifiers Support Immune System Health

Each airborne particle you inhale—whether it’s a pollutant, allergen, or pathogen—triggers a response by your immune system. By capturing those harmful particles and circulating clean air throughout your space, your body can focus on keeping your immune system strong day and night.

Breathing air that’s free from harmful particles is just one part of a wellness plan that should include ample sleep, plenty of purified water, and a balanced diet. 

Bottom Line

Air purifiers alone will not protect you from viruses, but they can contribute to an overall healthier indoor environment and better sleep. A purifier’s effectiveness depends on its ability to draw in contaminated air and circulate pure air throughout your entire breathing space or 'box.' Alen is proud to make top-rated purifiers that do just that—quietly and efficiently.

Alen provides a range of customizable True HEPA air purifiers so you can enjoy cleaner air and breathe better. Take a look at some of our best selling True HEPA air purifiers.


Alen HEPA Air Purifiers for the Home

Shop Now


Your wellness is our highest priority. If you have any additional questions or concerns, please contact our air quality experts from 8 a.m. to 6 p.m. CST M-F and 10 a.m. to 4 p.m. Saturday. Call 800-630-2396, email service@alen.com, or chat at alen.com.

IMPORTANT: Alen does not provide medical advice. Consult your doctor or a medical professional with healthcare questions.


Dan Mottola, Alen Content Marketing Manager 04/23/20

@Steve, Thanks very much for your insightful question. It’s top of mind for a lot of people.

Under most circumstances, we don’t think it is harmful to use HEPA material from an AIR PURIFIER filter in homemade masks given the COVID-19 situation. We believe that the value of using this material outweighs possible disadvantages. Here’s the critical detail: Air purifier filters typically do not contain the fiberglass found in certain HVAC filters, which can release harmful crystalline particles.

A HEPA filter is constructed of two or three layers consisting of the actual HEPA layer (which itself is fibrous), a melt or bonding layer, and a polypropylene backing layer required to hold the delicate HEPA layer in place. Polypropylene is essentially a woven sheet of plastic fibers of varying lengths to provide stiffness.

It is possible to ingest polypropylene fibers into your lungs, but the thread count of most common cotton and other synthetic materials makes it unlikely that the fibers can be separated from the backing and then make their way past that screen.

In the case of ingestion, the body cannot decompose these fibers in the same way as similar particles from other common plastic sources as cited in this and other research findings https://pubs.acs.org/doi/10.1021/acs.est.9b01517

So, while the full effects of possible ingestion are not yet known we are operating in unprecedented circumstances where the CDC, FDA, and medical facilities are welcoming PPE of this type and of even far less efficacy in light of the COVID-19 risks which are still not fully understand across patient populations.

To be clear, we cannot make a product claim for HEPA material in this use case – nor are we speaking for the industry. We as a company want to say as much as we can as soon as we can to help people to make their own informed decisions.

Steve 04/22/20

Dan – There is a small, family run company in the US selling masks with slot for an HEPA filter. They send along HEPA filters that are roughly 1/8th of an inch thick. Do you know whether or not it is advisable to have a HEPA fliter inside a mask up against your face? I’ve heard anecdotally that this may be a bad idea because it contains fiberglass. Any insight into this? Thanks.

Paul Morneau 04/22/20

Not mentioned in your article: If a virus is not captured by the HEPA filter in it’s first pass through the filter, it will be airborne longer (by the fan or blower in the air cleaner), thus potentially increasing the probability of someone inhaling it. Wouldn’t that suggest people who are sheltering at home and may have the virus should NOT use an air cleaner? Without careful studies, it is impossible to recommend either way.

Barbara Bopp 04/22/20

Can you recommend a safe method of removing for cleaning or replacing an Alen filter? A mask and gloves would help, but beyond vacuuming, but what’s the best way to minimize releasing particles into the air that might contain live virus/germs? I know that purifiers are not regulated, but can any scientists (CDC or on your staff?) make informed suggestions? Thanks—I’ve used and loved your purifiers for years and really appreciate your fair and balanced article.

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