What Are HEPA Filters Made Of? Answered!

Are you wondering what are HEPA filters made of and why they are recommended for allergy sufferers? High-efficiency particulate air is referred to as HEPA (filter). HEPA air filters are simple, despite how difficult they may sound. They are just a mat of randomly aligned fibers, produced from either glass or synthetic materials, and were created in the 1940s when scientists were working on the atomic bomb. The synthetic material used in the air filter is comparable to that found in T-shirts designed to dry quickly. So, what are HEPA filters made of?

A HEPA filter is an air filter for fibrosis commonly made of fiberglass, borosilicate glass, or plastic fibers (polypropylene). However, fiberglass air filters are made of glass, including silica, alumina, calcium oxide, boron oxide, magnesium oxide, and sodium oxide, among other materials.

What Are Hepa Filters Made Of?

Both HEPA filters and electrostatic precipitators contain the following components: a plastic housing, an electric fan to force air through the filter, the filter itself, and control switches to regulate the fan’s speed and turn the air purifier on and off. 

The borosilicate glass fibers or plastic fibers (like polypropylene) that make up the HEPA filters are joined together with a binder that contains up to 5% acrylic (the same compound that binds latex paint to a house). Electrostatic precipitators produce ions by passing extremely high positive direct current voltages through steel wires positioned between grounded steel charging plates. 

The most common types of plastic used to make cases include high-impact polystyrene, polyvinyl chloride, high-density polyethylene, and polypropylene. A post-filter made of activated carbon is often included with most air purifiers.


The size of the particles to be removed and the necessary air flow rate is considered while designing HEPA filters. The HEPA material’s pores vary in size, with smaller pores removing finer airborne particles. The filter material will clog more quickly and require replacement more frequently if it gathers finer particles, though.

The designer specifies the filter fabric’s mat density and glass fiber diameter, which determine the filter’s pore size. Binders that give HEPA filters more strength can be present. However, this results in a filter that clogs more quickly.

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An electrostatic precipitator is far more difficult to design. Home electrostatic precipitators typically have two parts: an ionizing section (where the electron cloud is generated) and a collecting part (where the charged dust particles are pulled out of the air). 

The collecting component is made up of several parallel steel plates, half of which are grounded and the other half of which carry a positive direct current voltage; hence, the plates alternately charge positively or negatively.

The ionizing unit consists of a parallel row of grounded steel ionizing plates placed in front of the collector plates and thin wires strung between them. The thin wires carry an extremely high positive voltage direct current (up to 25,000 volts in a home air purifier). 

The wires’ positive charges cause an electron flow between them and the nearby ionizing plates. Electrons are forced toward the wire by an acceleration of around 1,000 times greater than gravity due to the extremely high voltage on the wire, which causes the electrons to accelerate to extremely high velocities.

For instance, when a dust mite feces particle flies by a wire, high-speed electrons collide with the electrons in the particle’s molecules. Many of them are free. These molecules gain a positive charge as they lose electrons, attracting them to the negatively charged collector plate. 

For the ionized dust particles to be captured on the collector plates before the precipitator fan pulls them entirely through the air purifier, the designer must choose a high voltage to generate enough electrons to ionize the particles passing through the precipitator and space the collector plates closely enough apart.

HEPA filter Stops Particulates

The fibers of the HEPA filter are arranged in a manner that captures particles and keeps them from going back into the air. As air is driven past the filter, the particles are caught in 3 different ways:

  • Particulates first just run into the fiber and stick there.
  • Second, when particles approach the fiber of the filter by one diameter, they are pulled to the fiber and become trapped on it rather than flowing through it.
  • Third, a tiny particle (0.1 microns) moving through the filter collides with other molecules (Brownian motion), which causes it to become entangled in the fiber once more.
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HEPA air purifiers contain some activated carbon-based material to absorb odors and chemicals that the HEPA element cannot capture because pure HEPA air filters cannot remove odors, chemicals, or gasses.

Your HEPA system draws air in and filters it through the HEPA filter. HEPA Air Filtration Systems stop mold spores, bacteria, viruses, pet dander, and dust in addition to helping to remove hazardous gasses and odors from your home because they combine HEPA filters with carbon-based materials. When this air purification system exhausts, the air is clean and virtually free of contaminants.

GeneralAire Models 400D & 400R HEPA Air Filtration Systems are 99.97% effective at removing particles 0.30 microns from the air that passes through the HEPA filter, thanks to the incorporation of this technology.

HEPA Filter Efficiency

You must be aware of the HEPA filter type each air purifier utilizes to select one over the other. Therefore, you first need to find out how much of a particle the various HEPA filter types can capture.

Although this technology is very near, it is currently impossible to achieve 100% filtration because a HEPA filter only captures 99.9% of the Most Penetrating Particles (MPPS) between 0.12 and 0.25 microns.

Imagine how effective a HEPA filter is against particles larger than one micron, which are those particles that viruses typically have attached to. A HEPA filter can do this with the smallest and Most Penetrating Particle Size (MPPS). They are even simpler for the HEPA filter to capture and filter. Consequently, a HEPA filter’s effectiveness is almost 100%.

HEPA-Type Filter vs. True HEPA

A True HEPA filter is genuinely superior to a HEPA-type filter. Unfortunately, because of trademarking, a HEPA-type filter can be sold with false claims that it is as effective or nearly as effective as the True HEPA.

Only 0.2 micron-sized particles can be effectively captured by a HEPA-type filter, which only has a 99 percent efficiency rating. This may appear more impressive than the True HEPA’s 0.3 effectiveness, but it is not.

The MPPS (most difficult to capture particle) is 0.3 microns in size, and using True HEPA technology; the MPPS bounces into particles that are 0.1 microns in size. These smaller particles can be captured by them (usually viruses and bacteria such as the common flu virus).

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Can I Get A HEPA Filter?

The GeneralAire 400D (for duct installation) or 400R (portable room unit) HEPA Air Filtration Systems can improve your lives if you or someone else in your home has allergies or asthma.

According to studies, young children with asthma who had HEPA air purifiers in their bedrooms for almost four months saw fewer asthma symptoms. Even if your family does not experience asthma or allergies, simply breathing clean air might benefit you.

You want to purchase the best filter for your company, office, school, hospital, organization, or home to provide the cleanest and safest air possible. A True HEPA product is the best choice for achieving your air quality objectives.

True HEPAs have a longer lifespan and can run continuously for a full year. A strong, water-resistant True HEPA filter can efficiently eliminate dust, pet dander, pollen, bacteria, viruses, and other airborne contaminants.

Commercial Vacuums With HEPA Filters

HEPA filters almost minimize the possibility of dirt, dust, and other air pollutants being spread back into the air when utilized in professional floor cleaning equipment, such as vacuums. Particles may occasionally be released back into the air by equipment without a HEPA filter.

Commercial vacuums, for instance, remove dirt, dust, dander, and other extra soils that may worsen the indoor air quality (IAQ) in your building. If they don’t have a HEPA filter, some of the removed pollutants may also be reintroduced into the air while the vacuum’s air is circulated.

On the other hand, most of the pollutants that would typically re-enter the air will be captured and contained by the HEPA filter on your commercial vacuum.

A tight seal is necessary for the filter to filter the air as it moves through it completely. Air can evade the exhaust filter or filter bag without a tight seal. If that occurs, particles won’t be filtered out and will instead be sent back into the

Conclusion On What Are HEPA Filters Made Of?

High-efficiency filters, or HEPA filters, often catch over 99.5% of all airborne particulate pollution. Pollen, viruses, bacteria, mold, and PM2.5 can all be captured by these filters, which are either fiberglass or plastic (PP+PET). They are also very good at capturing nanoparticles, thanks to diffusion.

What’s significant about HEPA air filters is how well they work at removing particles of practically all sizes. They can gather allergens, pollen, PM2.5, viruses, germs, and more. The most crucial part of any air purifier is its HEPA air filters. I hope I have been able to answer your question on what are HEPA filters made of?