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What is a HEPA Air Filter?

woman opening her air conditioning unit

HEPA stands for high efficiency particulate arrestance. HEPA filters stop and capture at least 99.97% of particles that are 0.3 micrometers in diameter. This type of filter is designed to remove fine, invisible particles from the air.

With a HEPA filter, you can clean your air of pollen, pet dander, dust, dust mites, and other tiny particles. HEPA filters are particularly useful for purifying air for those with allergies or sensitivities.

How does a HEPA filter work?

diagram of how a hepa filter operates
The filter’s surface is built from a randomly woven mat of fibers. These fibers are 0.5-2.0 micrometers thick, slightly larger than the particles they are meant to trap. This filtration system works differently than most well-known types of filtration.

HEPA filters don’t operate like wire mesh or screens, where particles are too large to pass through the mesh or grid. Instead, three different physical properties take place when particles pass through fibers in the HEPA filter:

  • Interception, which is when particles pass so close to the fibers (less than a radius of distance) and get stuck to them.
  • Impaction, when particles are too large to respond to changes in airflow quickly and collide directly with fibers.
  • Diffusion, which depends on the properties of molecular movement. Since particles are so small, they move unpredictably. This, combined with the random movement of air, causes particles to be caught by one of the first two methods. This affects particles on the smaller end of the scale.

What’s the difference between an air purifier and HEPA filters?

Air purifier refers to the general type of device used to remove allergens, odors, or other impurities from the air. A HEPA filter is one specific type of air purifier. To be qualified as a HEPA filter, the device must remove at least 99.97% of all particles that are 0.3 micrometers in size. It can then be tested and receive HEPA qualification.

What separates HEPA filters from other types of purifiers is that specific qualification. Something important to note about HEPA filters, however, is that they do not purify odor from the air. Odor particles must be captured by filtration using charcoal or carbon elements.

HEPA filters are not antibacterial or antiviral by default. Though viruses and bacteria may be filtered by the system, there is nothing in the filter that will eliminate bacteria. Instead, a specific antibacterial treatment must be applied to the filter.

As an example, hospitals often aim Ultraviolet lights at their HEPA filtration units. This destroys living bacteria as they become trapped in the fibers of the filter.

Sources:
Wikipedia – HEPA
WebMD – HEPA Filters for Allergies

Ultimately, HEPA filters can provide a great deal of clean air if installed properly. Filtering out the majority of pollen, pet dander, and dust can help those with allergies breathe easier. If you’re looking to clean up the airflow in your home, schedule an appointment with us, and we’ll get you started with a super-efficient HVAC system that keeps your air free of pollutants.