Regarding the topic of what a HEPA filter is, many peers or manufacturers have already written about it. There are also many answers online. As a leading HPEA filter manufacturer, I still want to write about this topic and bring you some different information.
What is HEPA?
HEPA is the abbreviation of the first letter of “High-Efficiency Particulate Air.”
What is a HEPA filter?
Hepa filter generally refers to HEPA air filter. A kind of air filter that can filter out tiny particles efficiently, it is one of the many air filters.
Traditional definition: The efficiency of filtering particles with particles that are 0.3 microns is greater than or equal to 99.97%.
Its characteristic is that the air can pass through, but the fine dust can not. It was first introduced in 1940 by the U.S. Atomic Energy Commission in the Manhattan Project and was realized in the private military industry. Only in the 1860s was HEPA filtration declassified and allowed for commercial and residential use.
HEPA filtration was gradually introduced in operating rooms, isolation rooms, pharmaceuticals, and computer chip manufacturing, as well as in other locations where “absolute” filtration was required. Specifically, HEPA-compliant filters are 99.7% effective at 0.1 and 0.3 microns.
HEPA filters can remove particles with a diameter of 0.3 microns (1/200 of the diameter of a hair) or more with an efficiency of 99.97% or more. Those that meet this requirement are called TRUE HEPA, which is also the HEPA standard. If it does not meet this requirement, calling it a HEPA filter is incorrect.
Test method of HEPA filters
Regarding the HEPA testing method, it is recognized that it originated from the DOP method in the United States and has been adopted by many countries.
This was once the most commonly used method for testing HEPA filters internationally. The test dust source is 0.3-micron monodisperse phase dioctyl phthalate (DOP) droplets, also known as “hot DOP,” and the “amount” is the turbidity of the DOP-containing air.
The DOP liquid is heated into steam, condenses into tiny droplets under specific conditions, leaving 0.3-micron particles after removing the oversized and undersized droplets, and enters the air duct. The measurement instrument is mainly a light scattering photometer (photometer).
The primary filter materials used to make HEPA filters
The filter materials that can achieve genuine HEPA filters are PP fiber, glass fiber, plastic fibers, and PTFE.
These filter materials are made into pleated mechanical air filters by equipment.
The TRUE HEPA filters are used in residential and industrial applications, respectively.
Some applications of HEPA filters
HEPA filters made of PP and other synthetic fibers are commonly used in indoor or commercial public places such as office buildings, shopping malls, supermarkets, hotels, hospitals, schools, etc.
They are mainly installed in the HVAC system or indoor air purifiers. It removes airborne particles, human hair, and smaller particles to improve indoor air quality.
The HEPA filter is also the core component of the air purifier, used to filter pet dander and mold spores and to extend the HEPA filter’s usage life. A primary filter is usually installed before the HEPA filter to filter larger dust particles, and an activated carbon filter is used to adsorb some volatile organic compounds and other harmful gases.
These filters combine to form a small air filtration system, which can effectively improve indoor air quality and protect some indoor people, especially those who are allergy-prone and have asthma symptoms.
HEPA filters made of glass fiber are primarily used in industrial production, workshops, data storage centers, pharmaceuticals, semiconductors, etc. Some fields have very demanding requirements on the content of small particles in the air and need HEPA filters to filter out the tiniest particles.
The most penetrating particle size is 0.1-0.2um, which has very little inertia in the air, so only ultra-fine glass fiber with very small fiber diameters can be used in HEPA filters. The HEPA filter with fine mesh can filter them.
Therefore, the fiber’s fineness, the fiber’s diameter’s size, whether it is electrostatic, and the fluffiness of the filter material all have a crucial impact on the overall performance of the HEPA filter.
