A better quality of air, for a better quality of life A better quality of air, for a better quality of life Neutralizing gases that trigger hazardous corrosion Treating air emissions and nuisance odors Protecting mission critical equipment from air contaminants Every day, we protect people, processes, and environments with our chemicalWe are inspired to create a better world.HomeGuide Diffuser vs. Humidifier – Which Should You Buy? HEPA Filters and ULPA Filters Information Show all HEPA Filters and ULPA Filters Manufacturers High efficiency particulate air (HEPA) filters and ultra-low particulate air (ULPA) filters are air filters designed to trap a vast majority of very small particulate contaminants from an air stream. Air filters must satisfy certain standards of efficiency — most commonly those developed by the US Department of Energy (DOE) — in order to qualify as a HEPA filter. The US standard (DOE-STD-3020-2005) requires that a HEPA filter be capable of removing 99.97% of contaminant particles 0.3 μm in diameter.

Most standards also specify that HEPA filters must feature minimal pressure drop and maximum airflow when in operation. A filter's percent efficiency can be calculated using the simple equation below. E = percent efficiency D = downstream concentration (of contaminants) U = upstream concentration (of contaminants) Particle Size and Filtration Method While the US HEPA standard usage of 0.3 micrometer particles to describe efficiency may seem arbitrary, particles of this size are actually the most difficult to filter, rendering them a kind of "worst-case scenario" reference particle. The reasons for this difficulty in filtration are described below. HEPA filter media is made up of countless randomly-arranged fibers which together form a dense mat; when air flows through the filter, the media captures and contains contaminant particles throughout its depth. A fibrous filter's media as seen through an electron microscope. Filter fibers trap contaminants using three primary methods:

The three filtration methods described above (plus an electrostatic method). Understanding these three methods makes it clear why particles around 0.3 micrometers are most difficult to filter. Particles less than 0.1 micrometers are easily trapped due to diffusion while particles larger than 0.4 micrometers are trapped by inertial impaction. Particles between 0.1 and 0.4 μm are therefore too large for effective diffusion and too small for inertial impaction and efficient interception, so that the filter's efficiency drops within this range. air purifier and humidifier walmartBy specifying a HEPA filter's efficiency at 0.3 μm, standards bodies are really describing a variant of the filter's minimum efficiency.electrostatic air cleaner ionizer A HEPA performance graph, showing the steep drop in efficiency around 0.1 μm.honeywell air purifier hfd-120-q

While HEPA products designed for industrial, military, and government applications are explicitly certified, some cheaper consumer air purifiers and filters are marketed as "HEPA-type" and are often touted as capable of "removing 99.97% of dust and allergens" without specifying particle size. The growth of these marketing devices has led some manufacturers to use the term "True HEPA" to describe filters and purifiers manufactured and tested to DOE or EN standards. Ultra-low particulate (or sometimes "penetration") air (ULPA) filters are closely related to HEPA filters but are even more efficient. ULPA filters are specified to remove 99.999% of contaminants 0.12 μm or larger in diameter. The chart below shows the overlap in the capabilities of ULPA and HEPA filters. Image credit: Sentry Air Systems European Standards for HEPA and ULPA The European Union standard for both HEPA and ULPA filters — EN 1822 — classifies filters into different classes depending on their efficiency.

All EN 1822 specifications are based on a filter's ability to trap and contain the most penetrating particle size (MPPS) particular to the filter. The MPPS is typically determined by a laser spectrometer or electrostatic classifier. European filter classes and relevant specs are listed in the table below. Note the radical difference between the European and American definition of HEPA efficiency, particularly that the EU standard permits HEPA filters with efficiencies as low as 85%. Table source: AAF International HEPA and ULPA filters are used in applications requiring very efficient filtering of airborne pathogens which can cause aggravate asthma and cause allergies or disease. These filters are also useful in manufacturing environments which require very clean air. Standards are particularly important to the manufacturing, use, and testing of HEPA and ULPA filters. The standards listed below are commonly referenced. IEST RP-CC001  -- HEPA and ULPA filters

IEST-RP-CC007 -- Testing ULPA filters ASTM F1471 -- Standard Test Method for Air Cleaning Performance of a High-Efficiency Particulate Air Filter System Camfil Farr - A science-based approach to selecting air filters John Larzelere - New and novel technologies in particulate filtration Image credit: N.R. Murphy Ltd. | If your facility incorporates a laminar flow cleanroom, these MAGNEHELIC and PHOTOHELIC differential pressure gauges can help you maintain the positive pressure necessary to block inrushing contaminants that can damage sensitiveIn doing so, they also help to meet the requirements and recommendations set forth in FED STD 209E which specifies that a minimum positive pressure of 0.05" (1 mm) of water differential be maintained between the cleanroom These gauges incorporate an exclusive MAGNEHELIC Principle that eliminates wear, backlash, and hysteresis. is a remarkably high standard of accurate, dependable gauge

performance at a modest price. This MAGNEHELIC Principle is a method of transmitting the effects of changes in air pressure from a diaphragm to an indicating pointer—by means of magnetic linkage and without the use of gears or other direct mechanical linkages. This system avoids wear and physical contact, which might destroy the accuracy and sensitivity of the instrument. delivers accuracy to within 2% of full scale. This principle offers numerous advantages over other gauges. Because it uses no fluid, it eliminates evaporation, freezing,It also ensures inertia-free, drift-free pointer movement and offers unusually high resistance to shockThese gauges are also unharmed by pressure surges up to 15 psig and by ambient temperature fluctuations between 20 and 140 degrees F (-7 and 60°C) . Both MAGNEHELIC and PHOTOHELIC gauges feature easy-to-read 4" (102 mm) dials that quickly provide gas pressures—positive,

Because operation does not depend on gravity, you can either face- or flush-mount them in anyGauges can also be mounted on panels either inside or outside of the cleanroom; if mounted inside, the low pressure ports of the room pressure gauges can be connected together, and a single tube routed to outside the room. Use the MAGNEHELIC gauges (range of 0.25-4.0" WC) to determine positive pressure differentials between the cleanroomMAGNEHELIC gauges can also be used to measure pressure drops across pre-filters and absolute A PHOTOHELIC gauge/switch can also be used to control makeup or exhaust air dampers in order to maintain the room pressure within prescribed limits. All gauges can be mounted on a control panel. Gauge calibration is accomplished betweenIn this application the PHOTOHELIC gauge serves as the “master” gauge. These units can also be used to check air filters, to sense static pressure or to measure air velocity and volume.