What Is HEPA Filter And How Does It Work?

May 16, 2017
in Home

With the world’s carbon footprint increasing at a staggering pace, it has almost become a necessity to have a HEPA filter installed in your urban jungle home. Naturally, that brings us to the question, what is HEPA filter and how does it work? In this article, we will dive into the details and aim to answer every question you have regarding the HEPA filter.

What is a HEPA filter?

Let us begin by understanding what is meant by HEPA filter. High-efficiency particulate air (HEPA) filter, which was formerly called high-efficiency particulate absorber, is a type of air filter. According to the National Institute for Occupational Safety and Health (NIOSH), an air filter can only be a true HEPA filter if it can remove at least 99.97% of airborne particles that have a diameter of 0.3 microns.

As a consumer, you must avoid products that claim to be “HEPA-type”, “HEPA-like”, “HEPA-style” or “99% HEPA”. According to leading information resource unhumid.com, these products might not satisfy the requirements set by the NIOSH, and they are most likely not tested using the appropriate standards. That is why companies which follow the high standards set by NIOSH, market their products as “True HEPA” products.

Applications of HEPA filter

The following are some of the applications of HEPA filters:

· Air purifiers and dehumidifiers

· Industrial vacuum cleaners

· Exhaust filters in medical facilities

· Biological safety cabinets

· HEPA face masks

· Air filtration systems in airplanes

How does the HEPA filter work?

Now that we have got the boring definition out of the way let us see how a HEPA filter works. But first, we must get rid of a common misconception that a HEPA filter functions as a sieve. That comparison is erroneous and inaccurate.

HEPA filters are composed of a mat of randomly arranged fibers. The most common fiber material is fiberglass, and the thickness of these fibers are generally between 0.5 to 2.0 microns.

Key factors

The key factors that affect the functioning of a HEPA filter are as follows:

· The diameter of the fiber

· Thickness of the filter

· Face velocity

While membrane filters of a particular pore size, can only filter particles which are greater than the diameter of the pores; HEPA filters can filter particles much smaller than the average distance between two adjacent fibers. The airborne particles get stuck to the fibers through the following series of procedures:

Interception – In this process, the particles following a line of flow in the air stream get stuck to the fiber.

Impaction – This purpose of this mechanism is to filter out the larger particles which follow a curved stream of air. The larger particles get attached to the fibers and are unable to pass through it. This process becomes more effective with the reduction of the average distance between two fibers.

Diffusion – The smallest particles, those below 0.1 microns in diameter are slowed down by the collision with gas molecules. Thereby increasing the probability of getting pinned to the fibers by one of the above mechanisms. This process is more efficient at lower face velocities.

Now that you have a good understanding of the HEPA air cleanser and HEPA filtration process, you will be able to correct your friends who mistakenly compare this process to that of a sieve!