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What is a HEPA filter?

Searching for an air purifier? Perhaps you are thinking about a service to help the air quality in your home or office. If you’re looking around, “HEPA” is one label that you shouldn’t ignore. In fact, you want to search for products that include this certification. Once you see a product that says “HEPA-certified,” breathe a little easier.

The team at TruClean Home Services is here to help you have the best quality of living. It starts with clean air at home. Understanding HEPA-certified filters is one of the first ways to make more informed decisions about purchasing items like air filters for your home.

We’re all seeing HEPA a lot more these days. Is there value for consumers?

What Is HEPA?

HEPA stands for High Efficiency Particulate Air. It is a designation used for filters. Historians can trace HEPA filters back to World War II. During World War II, American scientists were collaborating on the Manhattan Project. While creating the atomic bomb, scientists created the first HEPA filter. Its goal was to capture the released radioactive particles.

Officials didn’t establish the HEPA standard and certification process until 1983. Today, HEPA filters are in common products, including cars. To have “HEPA-certified” in the product description is not an easy standard to meet. For a product to be HEPA-certified, the filter must be able to trap 99.97% of particles that are 0.3 microns in size. This designation is very specific.

What Is So Important About 0.3 Microns?

This measurement is the deciding factor for meeting HEPA standards. To receive a HEPA-certified label, a filter must be able to trap 99.97% of particles that are 0.3 microns. Why 0.3 microns? Ask scientists.

Particles that measure 0.3 microns are more likely to go through air filters. Scientists describe this measurement as the most penetrating particle size. Compared to other sizes, a size of 0.3 microns is the most difficult to trap. This includes particles that are smaller and larger.

What About Filters That Advertise Trapping 99% Of Particles?

Remember, not all particles are the same or as difficult to trap through filters. When filters meet HEPA standards, they are able to trap 99.97% of particles that are 0.3 microns.

Avoid the marketing methods that use a higher percentage in advertisements. Do a bit more research on the size of the particles. Although a filter may trap 99% of particles, are the particles larger in size and easier to capture? Ask questions. See if the advertised filter captures ultra-fine particles, too. Particles that are 0.3 microns are the more challenging particles to capture. This is what makes HEPA filters valuable.

How Does A HEPA Filter Work?

When you think of a HEPA filter, imagine a maze of glass fibers. You’re using these filters in your vacuum cleaners, your air filter, or even your car. As you breathe the air around, the goal is to cut the number of contaminants you may inhale.

As you picture a maze of glass fibers, it’s easy to guess that each fiber is twisting and turning. With this arrangement, it is much more difficult for particles to come through the air filter. HEPA filters remove particles in four ways: direct impaction, sieving, interception, and diffusion.

Direct Impaction

Did you know that some large contaminants travel in a straight path? When this happens, these particles run into the maze of glass fibers. Once they land, they are stuck to the filter and can stay far away from you and your family. Here are some examples of these large contaminants: certain types of pollen, mold, or dust. Each of these contaminants can be harmful to your health and your family’s health.


This filtration technique occurs when a particle gets stuck. That’s right — it lands between two fibers. The large size of the particle makes it too challenging to pass through the gap. Again, this is a win for the filter. One less group of particles is entering your air.


Although airflow can move around particles, you can’t forget about inertia. This property means that particles will continue moving on their original path. As a result, particles can stick to the sides of the fibers.


For small, fine particles, movement can be unpredictable. Although chaotic, this movement makes it easier for filters to trap particles. While scattering, particles are more likely to both hit and stick to the maze of fibers.

What about the fine particles that pass through a HEPA filter. Are they dangerous?

Thinking about the air that you breathe, you also think about the health of your lungs. There are dangerous contaminants that could have lasting health effects. Yes, a HEPA filter captures the more challenging particles to trap. There are some particles that will still escape, though.

They also won’t go unnoticed. With teamwork, other technologies are also working to trap fine particles. Examples include fumes, smoke, and more chemicals. Each of these contaminants could impact your health and your family’s health.

Are there types of HEPA filters?

While shopping for filters, you might see a few different types. You may also hear of a designation known as True HEPA. The term True HEPA has become more common in marketing. True HEPA highlights the differences between American and European HEPA standards.

American standards are typically viewed as True HEPA. To a consumer, here’s a big difference: the percentage. In Europe, for example, the standard rate for certification is 85%. A filter must capture this percentage of particles that measure 0.3 microns. Compare this to US standards. US filters must capture 99.97% of particles that are 0.3 microns in size to be HEPA-certified.

While looking around for your next filter, watch for other terms, too. If you see “HEPA-type,” “Ultra HEPA,” or other labels, keep shopping. These designations aren’t recognized by either American or European standards.

We’re here to help you make the best decisions about protecting the air quality of your home. Contact TruClean Home Services today. We can share more about the products and services we offer. Keep in mind that the air you breathe has a great impact on the health of your lungs. Let us help


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