HEPA Filters and ULPA Filters

High-efficiency particulate air (HEPA) filters and ultra-low particulate air (ULPA) filters are designed to screen particles larger than 0.3 µm. HEPA filters are 99.99% efficient in removing particles 0.3 µm and larger. ULPA filters are 99.9995% efficient in removing particles 0.12 µm and larger. When used with a prefilter, high-efficiency particulate air (HEPA) filters and ultra-low particulate air (ULPA) filters can last for several years in a cleanroom environment. Moreover, because airflow capacity decreases and static pressure increases over time, HEPA filters and ULPA filters can become more efficient as the filter loads.

High-efficiency particulate air (HEPA) filters and ultra-low particulate air (ULPA) filters are made of a spun-hooked glass fiber that is rolled into a paper-like material which is then pleated to increase its surface area. Both HEPA filters and ULPA filters are available from a variety of suppliers, many of whom comply with standards from organizations such as the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE); the American Institute of Architects; (AIA) and the Joint Commission for the Accreditation of Healthcare Organizations (JCAHO).

High-efficiency particulate air (HEPA) filters and ultra-low particulate air (ULPA) filters are used in air filtration and purification systems to control airborne particulate levels and to stop the spread of toxic agents and infectious diseases. HEPA filters are often used in HVAC systems, biological safety cabinets, laminar flow hoods, and healthcare facilities. Biological safety cabinets use HEPA filtration to exhaust contaminated air and prevent air from a surrounding area from contacting a work surface.

High-efficiency particulate air (HEPA) filters and ultra-low particulate air (ULPA) filters that are used with laminar flow hoods perform a similar function, but are not designed to control infectious diseases or toxins. Medical facilities such as isolation rooms, intensive care units (ICU), and operating rooms also use HEPA filters and ULPA filters to remove infection and contamination by airborne microorganisms such as molds and spores.

There are several important specifications to consider when looking for high-efficiency particulate air (HEPA) filters and ultra-low particulate air (ULPA) filters. These include porosity, efficiency, filter length, height and width or ring size, and ply. Filter porosity is measured in average number of pores-per-linear-inch (ppi). The range of ppi provides an open cell with little air restriction to fine-celled foam for maximum particulate filtration. Efficiency is the ability of HEPA filters and ULPA filters to remove a certain amount of particles of a certain size at certain airflow. Ply refers to the layers of media contained in the filter. Ply can be anywhere from one up to five and sometimes greater than five.

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