Understanding HEPA Air Filtration

Although HEPA air filtration has been in use since World War II, the interest in and demand for HEPA air filters has grown significantly in recent months as a result of the coronavirus. To understand what HEPA air filtration is, how it works, and how it can help prevent the spread of COVID-19, we spoke with Thomas Nagl, owner of Filcom Umwelttechnologie, a leading air filtration company in Austria.

What is HEPA Air Filtration?

HEPA is an acronym for high-efficiency particulate arrestance, or air filtration. “It means that, in order to meet the HEPA standard, a filter must achieve a specified efficiency,” explains Nagl. “When we talk about efficiency, we are typically talking about a HEPA grade of H13 or H14.”

H13-H14 HEPA are within the highest tier of HEPA air filtration and are considered medical-grade. “A HEPA grade of H13 can remove 99.95% of all particles in the air measuring 0.2 microns in diameter, while a HEPA grade H14 removes 99.995%,” says Nagl.

“The 0.2 micron is the most difficult size of a particle to capture,” explains Nagl. “It is known as the most penetrating particle size (MPPS).” Therefore, the expressed percentage is the filter’s worst case efficiency, and particles that are larger or smaller than 0.2 microns are trapped with even higher efficiency.

Note: Europe’s H ratings should not be confused with U.S. MERV ratings. The HEPA H13 and H14 in Europe is approximately equivalent to a MERV 17 or 18 in the United States.

What are HEPA Filters made of and how do they work?

Most HEPA filters are made of interlaced glass fibers that create a fibrous web. “However, recent developments in HEPA filtration include the use of synthetic materials with a membrane,” adds Nagl.

HEPA filters capture and remove particles through the basic process of straining and direct impact, but also through more complex mechanisms known as interception and diffusion, which are designed to capture a greater percentage of particles.

Which particles can a HEPA filter remove from the airstream?

The HEPA standard traps very small particles, including those that are invisible to the human eye, but harmful to our health, such as viruses and bacteria. Since the web of fibers in a medical-grade HEPA filter are extremely dense, they can trap the smallest particles at the highest rate, and are more efficient at removing harmful toxins from the environment.

For perspective, a human hair is between 80 and 100 microns in diameter. Pollen is 100-300 microns. Viruses vary between >0.1 and 0.5 microns. However, it is important to remember that, even though the H13 HEPA is considered 99.95% effective at removing particles in the air measuring 0.2 microns, this is the worst case efficiency. It can still remove particles that are smaller and larger. In fact, the process of diffusion is very effective for removing particles under 0.2 microns, such as the coronavirus.

Nagl is also quick to clarify that viruses do not live on their own. They need a host. “Viruses often attach to fine dust particles, so larger particles in the air can have viruses on them, too. With a 99.95% efficient HEPA filter, you capture all of them.”

Where are H13-H14 HEPA filters used?

As you might expect, medical-grade HEPA filters are used in hospitals, operating theaters, and pharmaceutical manufacturing. “They are also used in high-quality rooms and electronic control rooms, where you really need clean air. For instance, in the production of LCD screens,” adds Nagl.

Can an existing HVAC unit be upgraded to HEPA?

“It is possible, but it could be difficult to retrofit a HEPA filter in an existing HVAC system due to the higher pressure the filter element has,” says Nagl. In this instance, Nagl recommends installing an air recirculation unit to recirculate the air inside with an H13 or H14 HEPA filter.

Understanding HEPA Air Filtration

Although HEPA air filtration has been in use since World War II, the interest in and demand for HEPA air filters has grown significantly in recent months as a result of the coronavirus. To understand what HEPA air filtration is, how it works, and how it can help prevent the spread of COVID-19, we spoke with Thomas Nagl, owner of Filcom Umwelttechnologie, a leading air filtration company in Austria.

What is HEPA Air Filtration?

HEPA is an acronym for high-efficiency particulate arrestance, or air filtration. “It means that, in order to meet the HEPA standard, a filter must achieve a specified efficiency,” explains Nagl. “When we talk about efficiency, we are typically talking about a HEPA grade of H13 or H14.”

H13-H14 HEPA are within the highest tier of HEPA air filtration and are considered medical-grade. “A HEPA grade of H13 can remove 99.95% of all particles in the air measuring 0.2 microns in diameter, while a HEPA grade H14 removes 99.995%,” says Nagl.

“The 0.2 micron is the most difficult size of a particle to capture,” explains Nagl. “It is known as the most penetrating particle size (MPPS).” Therefore, the expressed percentage is the filter’s worst case efficiency, and particles that are larger or smaller than 0.2 microns are trapped with even higher efficiency.

Note: Europe’s H ratings should not be confused with U.S. MERV ratings. The HEPA H13 and H14 in Europe is approximately equivalent to a MERV 17 or 18 in the United States.

What are HEPA Filters made of and how do they work?

Most HEPA filters are made of interlaced glass fibers that create a fibrous web. “However, recent developments in HEPA filtration include the use of synthetic materials with a membrane,” adds Nagl.

HEPA filters capture and remove particles through the basic process of straining and direct impact, but also through more complex mechanisms known as interception and diffusion, which are designed to capture a greater percentage of particles.

Which particles can a HEPA filter remove from the airstream?

The HEPA standard traps very small particles, including those that are invisible to the human eye, but harmful to our health, such as viruses and bacteria. Since the web of fibers in a medical-grade HEPA filter are extremely dense, they can trap the smallest particles at the highest rate, and are more efficient at removing harmful toxins from the environment.

For perspective, a human hair is between 80 and 100 microns in diameter. Pollen is 100-300 microns. Viruses vary between >0.1 and 0.5 microns. However, it is important to remember that, even though the H13 HEPA is considered 99.95% effective at removing particles in the air measuring 0.2 microns, this is the worst case efficiency. It can still remove particles that are smaller and larger. In fact, the process of diffusion is very effective for removing particles under 0.2 microns, such as the coronavirus.

Nagl is also quick to clarify that viruses do not live on their own. They need a host. “Viruses often attach to fine dust particles, so larger particles in the air can have viruses on them, too. With a 99.95% efficient HEPA filter, you capture all of them.”

Where are H13-H14 HEPA filters used?

As you might expect, medical-grade HEPA filters are used in hospitals, operating theaters, and pharmaceutical manufacturing. “They are also used in high-quality rooms and electronic control rooms, where you really need clean air. For instance, in the production of LCD screens,” adds Nagl.

Can an existing HVAC unit be upgraded to HEPA?

“It is possible, but it could be difficult to retrofit a HEPA filter in an existing HVAC system due to the higher pressure the filter element has,” says Nagl. In this instance, Nagl recommends installing an air recirculation unit to recirculate the air inside with an H13 or H14 HEPA filter.