HEPA Definition

Definition

• HEPA stands for high efficiency particulate air. HEPA filters clean the air by removing particulate matter that contacts the filter as air flows through it. HEPA filters force air through extremely small channels to remove particulate matter equal to or larger than 0.3 microns from the air.

Benefits

• The high efficiency of these filters makes them ideal for use in places where clean air is important. HEPA filters are frequently used in hospitals to prevent the spread of bacteria and indoor air pollutants. They are also commonly found in clean rooms where even small amounts of dust could damage delicate electronics. HEPA filters even have a place in the homes of allergy sufferers where the absence of pollen and dust in the air is a must.

HIstory of HEPA

• HEPA filters are actually a product of the development of nuclear power during the Manhattan project. These filters were first used in the 1940s by the Atomic Energy Commission as a method for filtering radioactive particulates out of the air. Initially a classified part of the Manhattan Project, the codename for a project conducted during World War II to develop the first atomic bombs, these filters were later released to the general public for use in commercial and residential settings.

How it Works

• HEPA filters consist of a tightly interwoven fibrous mesh that captures airborne particles as they pass through the filter. Four methods known as: sieving, interception, impaction and diffusion are use to achieve this end. Particles captured by sieving are generally above five microns in size and are removed when they cannot pass the filter. Intercepted particles are removed from the air when they pass near a fiber and become lodged there while impacted particles fly into a piece of the filter and are caught. The process of diffusion describes the impact of Brownian motion on particles in the air. As the air diffuses throughout the filter, small particles are more likely to encounter and become stuck on a fiber in the filter.

Considerations

• True HEPA air filters are defined as mechanical style filters that capture 99.97 percent of particulate matter that is 0.3 microns or larger in size. Most household
  equipment labeled HEPA captures less than 99.97 percent of particulates at 0.3 microns. These systems are often referred to as HEPA-type filters and are commonly found in home HVAC systems and vacuum cleaners. True HEPA filters require specialized equipment that is capable of forcing air through their restricted airways. It also important to note that HEPA filters only clean particulates from the air leaving unwanted gases in place.