What Is A HEPA Filter? How Do HEPA Filters Work?

Last Updated on March 12, 2024

Air pollution is already bad enough as we spend so much time outside in the unrefined air. It’s high time we install HEPA filters inside our homes for better air quality. So, what is a HEPA filter? How do HEPA filters work?

HEPA filters are pleated automatic air filters meant to trap harmful particles. It has a fine mesh that traps pollen, dust, and even smoke after forcing the air through it.

And all of it depends on the pleats; they randomly create a mat of fibers that catches the small-scale filth. You’ll find HEPA filters almost in every air purifier. 

However, if you want detailed information regarding HEPA filters, keep reading until the blog’s end. 

HEPA Filter Types + Mechanisms of HEPA Filter Filtration

A HEPA filter can eliminate 99.97% to 99.9% of fluttering elements from the air around its territory. In addition, it can trap particles smaller than 0.3 microns in size.

And guess what? The efficiency of this equipment is based on its worst working quality. Which simply means you can expect at least 99.97% of purity in HEPA-filtered air.

Types of HEPA

The types of HEPA filters matter a lot when it comes to their working methods. Each type comes with different characteristics. Anyway, let’s take a look at those!


The HEPA filters that don’t meet DOE (Department of Energy) standards are considered to be HEPA-type and HEPA-like HEPA filters. They offer 90% of effectiveness.

H13 Medical Grade HEPA

It is specifically an advanced version of HEPA filters. Mostly it’s used in hospitals, and that’s why it’s named Medical-grade HEPA.

True HEPA Filter

True HEPA filters are the greatest HEPA filters ever. They clean the air while leaving zero airborne. Its efficiency level is 97.99%. This can trap particles of 0.3 to 0.1 microns in size. Let’s see how this filter works:

How does a HEPA filter work?

Method 1: Straining – Working with Larger Particles

The maximum size range of the true HEPA filter is 10 microns. But this is too big for air filters. As the particles would be too big to get through, they would get stuck between two of the HEPA fibers. It is called Straining. 

Method 2: Interception for Smaller Particles

The true HEPA filter is always on the trend. It can eliminate particles 0.3 microns in size from the air. And that’s how it captures the minor elements like bacteria. Well, small particles can easily get between the fibers.

But most of them are heavy, so they get stuck inside anyway. So the filter puts pressure on the lighter ones to lock them inside, and this is what scientists call Interception. 

Method 3: Diffusion of Really Small Particles

As we mentioned, HEPA can capture particles smaller than 0.3 microns. This might sound unrealistic. Actually, particles 0.1 microns in size have very little mass. Therefore, they bounce like pinballs when the gas molecules hit them and start moving in zigzag patterns due to Brownian motion. 

And the fibers of a HEPA filter are made in a way that they trap the particles the moment they hit the fibers. This technology is called Diffusion.

Mechanisms of HEPA Filter

Learning about the mechanisms of HEPA filters will help you understand the working methods of the filters. Let’s check those out!

Mechanical Filter

This one is made for capturing dust on the filter media. It is currently one of the most popular HEPA filter mechanisms.

Electrostatically Charged Filter Media

This filter media is designed judiciously. The working method of this one is increasing the efficiency of catching specks when they are positively or negatively charged. 

Electronic Air Cleaners (two-stage)

An electronic air HEPA filter mechanism will work by imposing charges on particles. The filter would use an external power source for doing so.

video credit: Sylvane

Why Do We Need HEPA Filters? 

Installing HEPA filtration and ventilation technology is one of the most significant concerns of house owners nowadays. And we find it very justifiable. To keep your indoor air clean, fresh, and germ-free, there is no other better way than a HEPA. 

Global Death Rate

Clean or purified air is not only an issue of safety and comfort around residential areas such as apartments and homes. Rather it is now a governmental requirement for commercial places in every city and country worldwide because air pollution has been audaciously killing thousands of people yearly. 

By improving the air quality, HEPA filters have already managed to lower the annual global death percentage caused by air pollution. Even though the number of people who use air purifiers is minimal, the utmost use of this machine can save us from every potential misery that vile air can jot down on the world’s fate. 

Save Thousands of Lives

Did you know there are spanless numbers of pathetical air pollution diseases that kill newborns? Lower-respiratory infections, brain damage, diarrheal diseases, inflammation, jaundice, and blood disorders are some of those.

But guess what? By installing HEPA filters, the death rates of newborn babies due to air pollution can reach zero.  

Not only kids, adults bitterly fall victim to several severe diseases due to this issue as well. Therefore, to save our lives from this discontent conclusion, we think everyone should consider the idea of installing HEPA filters. 

Frequently Asked Questions

  1. What is a HEPA Filter, and How Does It Work?

HEPA Filters are highly efficient air filters that eliminate 97.99- 99.99% of harmful particles from the air. Most people would think it works like a net. But what about the particles smaller than the holes of a net? Well, those go through the filter as well because HEPA works with Staining, Interception, and Diffusion methods.

  1. Do you leave HEPA filters on all the time?

Leaving a HEPA filter on all day has no side effects. Rather, it will clean the air around you thoroughly. Air filters use minimum electricity. Hence, you can leave it on 24/7, so there’s no room for toxic air inside your house. Otherwise, the air may get unrefined once you turn the purifier off.

  1. How are HEPA filters?

HEPA filters remove 99.9% of harmful particles from the air. And some of these are allergens, viruses, bacteria, dust, chemical compounds, and other life-threatening elements. So it needs no explanation that all of those can add fuel to the fire when it comes to people with asthma, allergies, or other respiratory issues. 

  1. Where are HEPA filters used?

HEPA filters are primarily found in contaminated areas such as hard disk drives, medical devices, semiconductors, food, nuclear and pharmaceutical products. They are also vastly used in hospitals, vehicles, and homes. It’s a matter of time before the increasing death rate due to air pollutants make HEPA filters mandatory.

  1. What are the types of HEPA filters?

There are three types of HEPA filters. HEPA-type, True HEPA, and H13 HEPA. HEPA-like filters are those which don’t hit DOE standards, true HEPA hits all necessary certifications, and H13 HEPA filters are used in hospitals.

  1. Which type of filter is used in the HEPA filter?

HEPA filters are made with pleated mechanical air filters. They are highly efficient and traps larger to smaller particles. And these filters last longer as well.

  1. How many types of HEPA are there?

There are 6 types of HEPA filters, according to IEST. A, B, C, D, E, and F. These types divide HEPA filters into three other types, HEPA-like, True HEPA, and H13 HEPA.

  1. What is a 3-stage HEPA filter?

The HEPA filters with carbon, VOC, and Pleated filters are called 3-stage HEPA filters. They can purify a room larger than 56 square feet in size. Moreover, you’ll get LED lights and timer functions with them.

Bottom Line 

Now that we’re at the end of our discussion, you know, “what is a HEPA filter? How do HEPA filters work?” we expect you to realize the significance of HEPA filters for keeping the air around us worth breathing in.

In today’s industrial era, making the air pure quickly is next to impossible. So if you want to live a happy and healthy life, you can’t help but rely on HEPA filters. Therefore, our recommendation for you would be to get air purifiers with built-in HEPA filters. 

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Paul M Walker

I, Paul M Walker, am the founder and the author of this little site you are currently on. I work to provide readers with no-fuss and easy-to-follow solutions regarding common air purifier and humidifier problems.

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