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What Is A HEPA Filter? How Does A HEPA Filter Work?

If you somehow landed on this page, you probably have seen the word "HEPA" gazillion times. Today, we are going to talk more about High-Efficiency Particulate Air AKA HEPA filter. For start, we will briefly go through about its history, where it is used, how does it work, and how to choose the right type. At the end of it all, we will even throw in the tips on how to extend a HEPA filter lifespan.
Short answer
HEPA filter trap 99.97% of the airborne irritants as small as 0.3 microns.

HEPA Filter Movement

What Is HEPA Filter?

HEPA filter is a type of mechanical filter that traps airborne particles as small as 0.3 microns (0.00001 in, 0.0003 mm) with 99.97 percent filtration efficiency. The filter performance is guaranteed and certified by DOE, IEST, and UL in the U.S. European standard has a lower filtration efficiency at 99.95%. All HEPA filter are officially labeled and must be produced and tested for quality assurance.

How Does A HEPA Filter Work And What Is It Made From?

HEPA filter works when air is pulled towards the filter. The filter fibers will capture passing particles at 0.3 microns or less e.g. mold, pollen, pet dander, dust mites, bacteria, and viruses. 0.3 um size is known to be the Most Penetrating Particle Size (MPP or MPPS) to bypass a filter. With harmful particles blocked and remove from the air, only clean air will be left floating. Allergic symptoms like sinus, cough, or breathing difficulty will gradually alleviate as the surrounding air is being filtered.

HEPA filter has a very narrow opening. Contaminants that pass through will be stuck on the fiber in either Direct Impaction, Diffusion, Sieving, and Interception. Direct Impaction happens when particles travel straight, collide and stuck with a fiber. Diffusion happens when ultrafine particles move volatilely, collide with fiber and stuck to it. Sieving happens when the particles are too large to pass through the gaps and gets ensnared by surrounding fibers. Interception happens when Airflow is rerouting the particles around the fibers, but will eventually stick to the sides of fibers.

HEPA is a fibrous filter made from interlaced fine glass fibers with a diameter of less than 1 micron. The fine glass threads are tangled and compressed in myriad directions to form a filter mat. There are multiple folded sheets of fibrous material that increase the surface area and efficiency of the filter. A normal HEPA filter will have around 2,500 layers of glass threads.

HEPA filter VS HEPA-type filter

The Differences Between HEPA VS HEPA Type Filter

True HEPA is rated at 99.97% efficiency in capturing particles as small as 0.3 microns. The cheaper HEPA-type filter has a lower 99% efficiency rate or less at particles as small as 2 microns. MERV wise, HEPA filter is rated between MERV 17-20 while HEPA-type is rated between MERV 13-16. Usage wise, the more expensive HEPA filter is commonly used in the upper-premium models like Winix, Blueair, Airmega. HEPA-type filter can be found in the compact models from the likes of Hamilton Beach, GermGuardian, Holmes.

In short, HEPA filter is the real deal if you want to filter microbes, bacteria, and viruses. Be warned though, there are many “imitator” in the market that use the word “HEPA” but is not a genuine HEPA filter. Study their specification carefully before making the purchase. To give you peace of mind, check out our best HEPA air purifier for a home guide.

Where Is A HEPA filter Used For?

HEPA filters are often used in applications that require airborne contamination control. Due to the effectiveness and constant improvement over the years, HEPA filter can also be found in the hospital, health care, and nursery home. It is regularly used in manufacturing plants such as FMCG, CPG, disk drives, and pharmaceutical. It can also be found in advanced industries e.g. aerospace, semiconductors, and nuclear power. For residential use, HEPA is the”IN” word that is often associated with an air purifier and vacuum cleaner.

Abbreviation for high-efficiency particulate air or high-efficiency particulate arrestance. The first-ever HEPA filter was created in 1940 by American scientists for the Manhattan Project during World War II. The purpose is to prevent the spread of airborne radioactive contaminants from the atomic bomb. Over the next decade, it was commercialized and became a registered trademark filter. In 1983, HEPA filter was officially certified with a specific standardization.

Max Fernandez

A loving father and a dedicated reviewer for airfuji.com with more than 1000 air purifiers under his belt. Max Fernandez is also one of the million patients currently suffering from asthma. Feel free to nudge him if you have any questions.