high-efficiency particulate air system
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What is a high-efficiency particulate air (HEPA) system?
A high-efficiency particulate air (HEPA) system is an air-filtration system that can capture at least 99.97 percent of airborne particles that are 0.3 micrometers or larger. HEPA filters do not work like membrane filters; instead, they use a pleated sheet of randomly arranged fiberglass fibers that typically have diameters between 0.5 and 2 micrometers. A motorized fan moves air through the filter, trapping particles as they stick to the fibers or become lodged in them.
HEPA filters were first created in the 1940s to capture airborne radioactive pollutants during the Manhattan Project. They were later sold to eliminate viruses, bacteria, fungi, pollen, and particulate matter in buildings. They are commonly used in hospitals, the aerospace industry, and within the home to maintain air quality.
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How does a HEPA air filtration system work?
HEPA (high-efficiency particulate air) systems filter air by trapping airborne particles. Unlike some filters, HEPA filters don't strain particles by size. Instead, a motorized fan forces air through a pleated sheet of randomly arranged fiberglass fibers, typically 0.5 to 2 micrometers in diameter, where particles adhere to the fibers or become embedded.
HEPA filters capture at least 99.97% of airborne particles that are 0.3 micrometers or greater in diameter. They are used in air-purifying systems, often with ultraviolet light to degrade bacteria and viruses, and activated carbon to adsorb volatile chemical molecules and control odors. These filters are essential in industries such as computer, electronics, aerospace, nuclear power, hospitals, and pharmaceutical manufacturing.
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What types of particles can a HEPA filter remove from the air?
HEPA (high-efficiency particulate air) filters are designed to capture at least 99.97% of fine airborne particles that are 0.3 micrometers (0.00001 inch) or larger. These filters can remove various particles, including viruses, bacteria, airborne fungi, pollen, human hair, smoke particles, pet dander, and dust from the air in buildings.
HEPA filters are used across various industries, including computer, electronics, aerospace, nuclear power, hospitals, and pharmaceutical manufacturing. They are also installed in aircraft and hospitals to limit the spread of airborne diseases.
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Where are HEPA air filtration systems commonly used?
HEPA (high-efficiency particulate air) filtration systems are commonly used across various sectors to maintain air quality. Developed in the 1940s for the Manhattan Project, they're now vital in industries like computer, electronics, aerospace, and nuclear power, as well as in hospitals and pharmaceutical manufacturing.
They are also installed in aircraft and in hospitals to restrict the spread of airborne fungi, viruses, and bacteria. Moreover, they can be found in homes as part of HVAC systems or as stand-alone units.
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What is the difference between a HEPA filter and a regular air filter?
HEPA filters and regular air filters differ primarily in their efficiency and design. HEPA systems must capture at least 99.97% of particles bigger than 0.3 micrometers, as specified by the U.S. Department of Energy.
Unlike membrane filters, HEPA filters use randomly arranged fiberglass fibers to trap particles through adhesion or embedding. Air passes through the filter via a motorized fan. While HEPA filters trap particles, they don't dispose of them; therefore, they often include processes such as ultraviolet light or activated carbon to degrade bacteria, viruses, and odors.
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Why are HEPA air filtration systems important for health and safety?
HEPA (high-efficiency particulate air) filtration systems are important for health and safety because they remove viruses, bacteria, airborne fungi, pollen, human hair, and particulate matter like smoke, dust, and pet dander from the air. These filters capture at least 99.97% of airborne particles that are 0.3 micrometers (0.00001 inch) or larger.
Developed in the 1940s for the Manhattan Project, HEPA filters are now used in hospitals, aircraft, and industries requiring clean air, such as computer, electronics, aerospace, and nuclear power. They help limit the spread of airborne diseases and are often paired with UV lights to kill trapped bacteria and viruses.
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high-efficiency particulate air system (HEPA system), particulate air-filtration system designed to capture at least 99.97 percent of fine airborne particles larger than at least 0.3 micrometre (0.00001 inch; 1 micrometre = 10−6 metre), as specified by the United States Department of Energy (DOE) and the European Committee for Standardization. The European standard is similar to the DOE standard; however, it defines five HEPA classes—H10 through H17—of increasing efficiency. The term HEPA filter refers not to a specific filter design but to the specific level of efficiency (i.e., 99.97 percent).
History and use
HEPA filters were developed in the early 1940s and used first by the Manhattan Project to contain the spread of airborne radioactive contaminants. HEPA filters were introduced commercially in the following decade to eliminate viruses, bacteria, airborne fungi, pollen, human hair, and particulate matter (such as smoke particles, pet dander, and dust) from the air in buildings. HEPA filters grew in popularity and necessity as technological advances that accompanied the Cold War saw the growth of industries in need of highly efficient air filters, such as the computer, electronics, aerospace, and nuclear power industries. Hospitals and pharmaceutical manufacturers also kept the filters in high demand, while the emergence of strict air pollution laws in the United States and other countries beginning in the 1970s raised awareness about the importance of clean air.
HEPA filters have been installed in aircraft and in hospitals, greatly restricting the spread of airborne fungi, viruses, and bacteria. Aircraft filters help slow down the spread of diseases from city to city. HEPA filters in hospital settings and in other medical uses are typically rated higher than the DOE standard—often at 99.99 percent efficiency, H14 in the European system—and equipped with high-intensity ultraviolet lights that kill any bacteria and viruses that the filters trap.
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Design
Unlike membrane filters, HEPA filters do not rely on the action of sieves or strainers, catching anything larger than a certain size while the rest passes through. Instead, they typically involve a pleated sheet of randomly arranged fibreglass fibres with diameters usually between 0.5 and 2 micrometres (between 0.00002 and 0.00008 inch). A motorized fan passes air through the filter, where particles are trapped when they adhere to the fibres or become embedded in them. The smallest particles collide with gas molecules. Such collisions slow the passage of those particles through the filter and increase their likelihood of becoming trapped.
Air-purifying systems equipped with a HEPA filter trap particles; they do not dispose of them. Consequently, HEPA systems usually employ other processes as well to complete their work, such as high-energy ultraviolet light for degrading bacteria and viruses and a fan or other forced-air system to ensure that the air passes through the filter. Activated carbon is often used to adsorb small volatile chemical molecules, converting them to a solid state from a gaseous one; this has the additional effect of odour control. Ionizer purifiers, frequently sold for home use, generate electrically charged gas ions that attach to airborne particles and cause them to stick to a collector plate. Those devices also can be used in conjunction with or as an alternative to HEPA filtration.