A Straightforward Look at the Complexities of Airborne Viruses

With the global outbreak of novel coronavirus (COVID-19), many are wondering whether air purifiers can help combat 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

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

“We believe air purification provides additional support to your body’s most important tool for fighting viruses—a healthy immune system,” said Alen CEO, Andy Graham. “It’s a passive, ‘always-on’ way to improve the overall health of a breathing space that doesn’t require major lifestyle changes.”

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 Really Works

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 (they must remove 99.97% of particles 0.3 microns and above). Filters are commonly perceived as nets or a screen that will stop objects larger than the smallest holes while letting air through.

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.


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 trapped in the HEPA filter’s maze-like fibers. In a process called diffusion, while larger particles travel in a straight line, 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.

HEPA filters can remove a portion of airborne particles such as COVID-19 and other flu viruses. But the extent of removal that may be truthfully claimed can only be done by proxy tests in controlled environments.

In our independent testing, Alen True HEPA filters captured 99.99% of airborne particles (including aerosolized viruses and bacteria) as small as 0.1 microns.

Of course, this would not include virus particles that remain alive for periods of time on surfaces open to touch.

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.

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.

Since health experts are advising more and more people to stay home, a HEPA air purifier can play a significant role in minimizing airborne transmission and supporting overall wellness with cleaner air in commonly-used indoor spaces.

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

Why Filtering Airborne Viruses is Just One Part of Prevention

Given justified concerns over the spread of COVID-19, there are some who have suggested that air filtration is ineffective and instead make other recommendations. We believe this is a false dichotomy. Protective measures are both reasonable and cumulative; both/and rather than either/or. Why not take an all-of-the-above approach to virus protection?

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, like a cough or sneeze, according to a  new study. On surfaces, it remains viable for up to three 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, good hygiene, and a balanced diet. Additionally, using proper hand washing techniques can help you avoid infection from viruses such as COVID-19, colds, and the common flu.

Many Alen filters feature an antimicrobial coating capable of killing 99.9% of E. Coli and Staph bacteria plus black mold.

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 HEPA air purifiers here.

Alen Air Purifiers Designed For Every Need

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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 [email protected] , or chat at alen.com.

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