What is a HEPA Filter and How Does it work?

Do you want to purchase a new vacuum or air purifier and confused about this ‘HEPA filtration’ phrase? Don’t worry; we will break it down for you.

HEPA filter is a High-Efficiency Particulate Air filter. HEPA filters stand out from the competition from other filters because they back up their claims. These filters must undergo testing and approval before they can be referred to as a True HEPA filters.

A HEPA filter must capture 99.97% of particles 0.3 microns or bigger. This is only the cut-off that must be met to bear the HEPA designation; it does not indicate that the filter cannot capture particles smaller than 0.3 microns, as many HEPA filters can.

The next sections in this article contain detailed information regarding HEPA filters:

What is a HEPA Filter?

what's hepa filter

A HEPA filter is a high-quality air filter that satisfies the HEPA filter standard. They are better known as anti-allergy filters since they are known to trap and remove pollen, mold spores, fine dust, pet dander, and other allergens and germs from the air.

HEPA filters can significantly impact if you or a family member has asthma or severe allergies.

A HEPA air filter traps microscopic and macroscopic particles using a highly compact fiber comprising thousands of incredibly thin fibers woven intricately.

In theory, HEPA filters can capture almost 99.97% of airborne particles that are 0.3 microns in size or smaller. 

A particle with a diameter of 0.3 microns is very small when considering 10,000 microns in one centimeter.

The common use of HEPA filters is in a household — HEPA filters are utilized in vacuum cleaners and in industry fields that need exceptional air quality, including aircraft, medicine establishments, nuclear power, and computer chip manufacturing units.

What does HEPA stand for? Where did it come from?

The full form of the abbreviation HEPA is “High-Efficiency Particulate Air” or “High-Efficiency Particulate Arrestance.” This abbreviation refers to a filter produced, examined, and approved per the construction, performance, and certification requirements set out by the Institute of Environmental Sciences and Technology.

During World War II, the Atomic Energy Commission created the first HEPA filters for factories making parts for the Manhattan Atomic Bomb project. 

The initial purpose of these HEPA filters was to remove minuscule radioactive particles that were too small to be effectively removed by other types of filters. Modern HEPA filters are far more effective and cost-effective than those created in the 1940s.

Why 0.3 microns?

A standard air filter often removes medium-sized to bigger particles from the air, but they lack the HEPA’s ability to remove extremely small micron-sized particles.

It is more challenging to filter particles with smaller micron sizes. Because pollen, allergens, and bacteria may be as tiny as 0.3 microns, the vacuums and air purifiers must utilize industrial HEPA filters with a 0.3-micron pore size.

Since 0.3 microns is the recognized Most Penetrating Particle Size (MPPS), filtering effectiveness rises for bigger and smaller particle sizes. A HEPA filter’s removal effectiveness rises as particle sizes fall below 0.3 microns.

The removal of even the tiniest particles from the airflow is crucial in many critical industries and in the case of severe allergies. If adequate filtration is not employed, respiratory and airborne illnesses can spread quickly. 

True or Absolute HEPA Filters

True or Absolute HEPA filters are interchangeably used for the same filter. True HEPA is the highest level of physical air filtering employed by hepa air purifiers. These filters are used in various settings and appliances, such as vacuum cleaners, cars, and airplanes.

Airborne particles are measured in microns, one-millionth of a meter. Anything smaller than 10 microns is microscopic to the human eye. The diameters of other particles, including dust, pollen, germs, and viruses, all fall in and around 0.3 microns.

The smallest particle that may enter your lungs is 0.3 microns in size; hence a HEPA air filter must be certified to remove 99.97% of all minuscule particles to be considered a True HEPA filter.

The Difference Between True and HEPA-Type Filters

To choose the right filter, it is critical to understand the difference between HEPA and True HEPA air filters. True HEPA air filters essentially collect up to 99.97 percent of particles as small as 0.3 microns, including various pollutants and allergens.

However, a filter with a HEPA Type filter can capture 99 percent of particles that are 2 microns or bigger, including dust and pet dander.

These particles are too small to be seen by the human eye, yet they are big enough to get into your lungs and trigger serious problems.

How Does a HEPA Filter Work?

HEPA filters capture air particles, pollutants, and allergens in an intricate network of fibers. This can occur in one of four methods; the method depends upon the particle size: inertial impaction, diffusion, interception, or sieving.

For understanding, we assume there are three kinds of particle sizes present in the air, now looks at their method of filtration:

Large particles

Larger particles are trapped via inertial impaction and sieving. The particles are either stuck after colliding with the fibers or are trapped while attempting to pass through them.

Medium-sized particles

The fibers intercept medium particles as they pass through the filter and are then collected. This method of filtration is called interception.

Small particles

As they go through the filter, small particles start moving in a zig-zag motion (due to their extremely small mass) through the gaseous medium.

Because of this special motion, theorized as Brownian motion, these particles can’t escape out of the hole of the filter and end up becoming trapped. This method is called diffusion.

Where Are HEPA Filters Used?

In general, HEPA filters are required for applications where minute airborne particles or bio-pollutants might risk consumer health or degrade product quality. Military establishments, nuclear facilities, and pharmaceutical industries typically use HEPA-type filters.

All the talk about HEPA filters is because of their use in vacuum cleaners. These specialized vacuum cleaners are called anti-allergy vacuum cleaners as they can trap allergens, molds, and animal dander, which many can feel allergic to.

Since all the air entering the vacuum travels through whatever dust and particles are gathered in the bag or bin before being vented back into your air, vacuum cleaners with HEPA filtration are particularly significant.

 Personal air purifiers and air circulators/purifiers are other usages of HEPA filters, all intended for routine or everyday usage.

Can HEPA Filters Capture Nanoparticles?

A conventional HEPA air filter is capable of capturing particles that are even smaller than 0.1 m. This strongly implies that Nanoparticles, which are classified as those smaller than 0.01 microns, can be captured by HEPA filters.

First, for those folks who want to get a perspective of how big a nanoparticle is, it is like 1/1000th time the diameter of a human hair.

When these tiny particles collide with gas molecules present in the air medium, they do not travel linearly; instead, they bounce around, a phenomenon known as Brownian motion. So, they go about in irregular patterns at increasingly fast speeds. 

Usually, they should readily pass-through HEPA filters since these particles are so minute. But since they don’t fly in straight lines but zig-zag patterns, they hit the fibers and become trapped inside the filter’s fiber.

This whole phenomenon is known as diffusion. Due to this phenomenon, HEPA filters are able to catch particles that would otherwise pass through their filter media’s holes.

Final Thoughts

HEPA filters are engineered to be highly effective in capturing small particles. By lowering airborne allergens, HEPA filtration improves indoor air quality in buildings.

If you are allergic or the elders in your home are dealing with respiratory ailments, it’s a wise choice to incorporate home appliances with HEPA-certified filters.

Robbert Randy

Robbert is an expert in vacuums. He graduated from the University of Applied Science with a degree in Commercial Economics in 2019. He tests and provide troubleshooting tips to vacuum users on his website. He don’t do this for profit–he simply want to research the best models out there and share his findings.

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