Everything You Ever Wanted to Know About HEPA Filters

Bry'Ana Arvie
Written by Bry'Ana Arvie
Updated November 7, 2022
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Photo: BGStock72 / Adobe Stock


  • HEPA filters trap 99.97% of airborne particles like dust and pollen at 0.3 microns.

  • They can improve indoor air quality and minimize pet allergens.

  • They alone are not effective against small particles, gases, and odors.

  • HEPA filters are available to consumers via air purifiers, vacuum cleaners, and HVAC systems.

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When your current indoor air quality just isn’t doing it for you anymore and you’re tired of rubbing your eyes and nose because of allergies, you may need a HEPA filter. Find out in this guide why they’re one of the most effective filtration systems on the market, how they work, their pros and cons, and what products commonly have them.

HEPA Filters and How They Work

An air purifier in cozy white living room
Photo: 220 Selfmade studio / Adobe Stock

According to the U.S. Environmental Protection Agency (EPA), a high-efficiency particulate air (HEPA) filter is a pleated mechanical air filter. It filters out at least 99.97% of airborne particles such as dust, pollen, bacteria, and any particle that’s the size of 0.3 microns. 

Why that specification? Because particles 0.3 microns in size are the hardest to trap. Particles larger or smaller than 0.3 microns are easier to capture, so the rating is based on how well a filter can capture the worst-case particle size in the worst-case efficiency—e.g., 99.97%. And to help you picture how big 0.3 microns is, a human hair is 50 to 180 microns. Small, right?

HEPA filters are made from fine polypropylene or fiberglass fibers tangled together. Let’s break down how this arrangement works to remove airborne particles.

  • Inertial impaction: This filtration phase happens when larger particles moving in a straight line collide with the filter media. 

  • Interception: This happens when tiny particles move with the air because they lack the inertia to move in a straight line; they eventually stick to the filter’s fiber.

  • Diffusion: The random movement—Brownian motion—of the smallest particles causes them to collide with gas molecules in low airflows, resulting in this filtration phase. 

Types of HEPA Filters

3 HEPA filter types compared, with Absolute HEPA filtering up to 99.99% at 0.3 microns

Not all HEPA filters are the same. Let’s look at what makes each one different.


Ever thought those knock-off shoes you saw at the mall look like the name-brand version it’s imitating? Almost, but just not quite the real thing, right? That’s how HEPA-like or HEPA-type filters are: They claim to be similar to HEPA filters, but they don’t meet the standard or testing requirements to be one. 

True HEPA 

Anytime you see a product with a True HEPA filter, it means it meets the standard set to be qualified as a HEPA one. These filters have been tested and can capture 99.97% of airborne particles at 0.3 microns. 

Absolute HEPA

Like True HEPA, Absolute HEPA is also tested and verified that its filters meet the HEPA filtration standard. However, they claim to filter 99.99% at 0.3 microns.

H13 and H14 HEPA

True HEPA filters are generally classified as H10 to H12, also known as the HEPA grade or efficiency level. True and Absolute HEPA filters are commonly found in household products, while H13 and H14 HEPA are medical-grade filters. These filters have been tested and can trap 99.95% to 99.995% of particles at 0.1 microns. At this rating, they’re effective against all bacteria, viruses, asbestos, and tobacco smoke.

Benefits of Using HEPA Filters

How can a HEPA filter benefit your life? Let’s cover that here.

Improve Air Quality

Allergens such as dirt, dust, and pollen are common problems for most homeowners, resulting in poor indoor air quality. If you’ve ever had a stuffy nose that seemingly came out of thin air or you couldn’t stop sneezing, you’ve been on the receiving end of allergen-induced respiratory issues. And if you have asthma, a newborn baby, or are sensitive to common allergies, you and your family can be much more affected by low air quality.

HEPA filters trap these indoor allergens while they’re still airborne so you can breathe easier with cleaner air.  

Minimize Pet Allergies

Your four-legged family members are as playful as they are lovable. But, for homeowners or those family members that get around on two legs, allergies caused by pet dander found on the carpet, sofa, or furniture are problematic. When you use a HEPA filter product, you reduce the chance of experiencing pet allergies.

Where HEPA Filters Fall Short

While HEPA filters can make a noticeable difference in your indoor air quality, they don’t solve all airborne-related problems. Let’s look at some situations where they miss the mark. 

Can’t Trap Gases and Odors

Gases and odors from standard cleaning supplies, craft material, and hair products can contain Volatile Organic Compounds (VOCs). According to the EPA, VOCs emit gases that may cause short- and long-term adverse health problems, like headaches, irritation of the eyes, nose, and throat, and liver damage. And while these are airborne particles, they’re too small (less than 0.3 microns) for HEPA filters to capture and help improve your indoor air quality. 

Aren’t Effective Against Small Particles

Similar to gases and odors, viruses are smaller than the standard set for HEPA filters, so they can’t effectively trap some viruses. The same is true for some bacteria. While they can capture some bacteria and viruses, those too small will simply slip through the fiber.

Product Types Using HEPA Filters

HEPA filters have always been a staple piece for the car, airline, and medical industries. But they can play a valuable role in your daily life as well. Some household products with HEPA filters are air purifiers, vacuum cleaners, and HVAC systems.

Each of these products helps minimize the number of airborne particles in your home in slightly different ways. Portable air purifiers capture airborne particles in one room, while HVAC systems filter out airborne allergens from the entire house. And vacuum cleaners prevent particles that have already settled on your floor from becoming airborne while vacuuming.

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