HEPA Filter: What is it? And how does it work?

hepa filter

Particle filters, particularly ones like HEPA, have been garnering a lot of attention in the media since the SARS-CoV-2 (Covid-19) virus started the pandemic.

In theory, filtering very small particles is relatively simple: all we need is a sieve with small enough pores to restrict the passage of the particles we wish to block. We could even use a sieve with no holes to prevent any particle, no matter how minuscule, from passing through.

What does HEPA stand for, and where did it originate?

HEPA stands for High-Efficiency Particulate Air, and it’s a term for filters that can collect 99.97 percent of particles smaller than 0.3 microns. Though the HEPA standard and certification process were not established until 1983, the first HEPA filter was created during World War II by American scientists working on the Manhattan Project to trap radioactive particles emitted during the development of the atomic weapon.

What is the significance of 0.3 microns?

Scientists refer to that micron size (0.3) as the MPPS or most penetrating particle size. Scientists discovered that particles that are small evade air filters more than particles that are larger or smaller. In a moment, we’ll explain why.

How do HEPA filters operate and what components are constituted to make them?

Most current HEPA filters are made up of interwoven glass strands that are twisted and rotated in a maze-like pattern. Particles are taken out of circulation as they go through this network in the following ways:

Direct Impaction: Sized-up pollutants like dust, mildew, and pollen travel in a straight line, collide with fiber, and stick to it.

Sieving: A particle is carried between two fibers by the air stream, but the particle is larger than the gap and becomes entangled.

Interception: Airflow is extremely nimble to go through and back out of fibers, but due to inertia, particles adhere to the sidewalls of fibers and continue on their course.

Diffusion: Because small, ultrafine particles move more irregularly than bigger ones, they are more likely to collide with fibers and attach to them.

What happens if particles go past a HEPA filter?

Other technologies, such as smoke, fumes, and other chemicals, can be used in conjunction with HEPA filters to protect against various ultra-small pollutants. Small pores in activated carbon filters collect chemicals, smells, and smoke that a HEPA filter could miss.

Are there various types of HEPA?

Air filters are referred to by a variety of terms. True HEPA is a marketing slogan that many people use to distinguish between American and European HEPA standards. To be HEPA-certified in Europe, a filter must capture 85 percent of particles sized at 0.3 microns, compared to 99.97 percent in the United States. As a result, the American standard is frequently referred to as “True HEPA.” Accrediting agencies in the United States and Europe do not recognise terms like “HEPA-type,” “Ultra HEPA,” and other HEPA variations.

What are the applications of HEPA filters?

HEPA filters were designed to be utilized in laboratories and factories. They’ve made their way into consumer devices such as vehicles, vacuum cleaners, and air purifiers in recent years. Because HEPA filters are deemed ideal for most biological applications, including healthcare, they are considerably more widely employed. Consider how viruses, which are tiny than 0.3 micrometers and theoretically, may pass through a HEPA filter, are most typically carried on larger particles such as saliva or perspiration, and thus are caught.

What to Look for in HEPA Filters in Air Purifiers?

In an air purifier, HEPA filters are the most prevalent type of filtration. Consider extra purification systems when purchasing an air purifier and filter for your home. Although the HEPA filter is usually the first line of defense against airborne particulates, it can enhance your air quality even more and extend the life of the HEPA filter when combined with extra cleaning. Installing one or more low-efficiency disposable pre-filters outside of a HEPA filter can extend the life of the HEPA filter by up to 25%.


Smoke, dust, germs, pollen, and other particles are typically captured by HEPA filters. These filters keep us safe from potentially dangerous contaminants in our homes and other indoor places. Although HEPA filters were originally designed to protect against radioactive particles, their commercialization has allowed them to be utilized by ordinary people in a more diverse way.

If you’re mostly concerned with bigger particles and want to buy a HEPA filter, pay close attention to the specifications when shopping for a purifier, as HEPA doesn’t always mean HEPA. Most essential, make sure to replace the filters on a regular basis, as living pathogens such as mold can survive and reproduce on the filter surface. Bacteria and mold development can even populate particulate filter media such as HEPA with higher moisture levels and elevated temperatures.

If you’re looking for a HEPA-powered air purifier, check out Servotech’s latest advent the UV Air Purifier:

Leave a Reply

Your email address will not be published. Required fields are marked *