What is a HEPA Filter?

In a world where you are only a few breaths away from inhaling pollutants of various kinds, air purifiers sure come in handy. If you were walking down the aisle of a store, looking for an air purifier to get, then you must have come across the words ‘HEPA filter’ as it is one of the most common types of air purifiers. In the simplest of terms, this post breaks down what a HEPA filter is, how it works, and everything else in-between.

What is HEPA?

HEPA is an acronym for ‘High-Efficiency Particulate Air’. It is also often referred to as ‘High-Efficiency Particulate Absorbing’. This means that as its name already implies, a HEPA filter is one that has high efficiency. The high efficiency, in this case, is the fact that a HEPA filter is capable of trapping as much as 99.97% of particulates that are 0.3 microns or larger. This does not mean that a HEPA filter is not capable of trapping microns lesser than 0.3 microns. 0.3 microns is simply the threshold the filter must pass before it can be regarded as one with high efficiency. These microns are of particular significance because it has been found that it is easier for them to evade air filters.

What is a HEPA filter made of?

The filter consists of a complex maze of glass fibers with varying diameters. The glass fibers have been entwined and arranged in different directions to give a complex web that even the tiniest of particles would find hard to evade.

How does HEPA work?

As already stated, the uniqueness of a HEPA filter is in how efficient it is in trapping the tiniest of particles. If you are already wondering how it carries out this task efficiently, here’s how.
The mechanism that would be used is dependent on the size of the particle. When a HEPA filter air purifier is turned on, it starts to suck in air. As the air is being sucked in, the particles begin to interact with the filter. It then gets the job done in either of these four ways.

Direct Impaction

This is the mechanism often used for large particles such as pollen, dust, and mold. Once sucked in, they move through the air purifier in a straight path. They then collide with and get trapped by the fiber in the HEPA filter.


This mechanism works best for tiny contaminants, those that are about 0.1 microns in diameter and even less. As they tend to move more randomly due to their size, it becomes easier for the air stream being released to cause them to get stuck to the fibers of the HEPA filter.


Sieving works for larger particles. The airflow causes the particles to travel between two fibers. However, because the gap between both fibers is smaller than the size of the particle, the particle then gets trapped between the gap.


Medium-sized particles tend to be able to brush by the fibers of the HEPA filter due to the movement of air. However, due to inertia, these particles can stay on course and get stuck to the sides of the fibers.

What kind of particles does a HEPA filter take care of?

A HEPA filter is effective against a wide range of contaminants and particles. From bacteria to mold to viruses to spores to dust to pollen and pet dander, the filter is pretty much very efficient.

With a HEPA filter, you no longer have to worry about the quality of the air you are breathing in. Its efficient absorbing properties would see to it that you breathe in a cleaner and contaminants-free air.

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