HEPA#Vacuum cleaners

File:Filter collection mechanisms.svg, interception, inertial impaction, and electrostatic attraction (air flow direction from left to right)]]

File:Filteration Collection Mechanisms-en.svg

HEPA filters are composed of a mat of randomly arranged fibers.{{Cite book |last1=Gupta |first1=Shakti Kumar |title=Modern Trends in Planning and Designing of Hospitals: Principles and Practice |last2=Kant |first2=Sunil |date=2007-12-01 |publisher=Jaypee Brothers |isbn=978-8180619120 |pages=199 |oclc=1027907136}} The fibers are typically composed of polypropylene or fiberglass with diameters between 0.5 and 2.0 micrometers. Most of the time, these filters are composed of tangled bundles of fine fibers. These fibers create a narrow convoluted pathway through which air passes. When the largest particles are passing through this pathway, the bundles of fibers behave like a kitchen sieve which physically blocks the particles from passing through. However, when smaller particles pass with the air, as the air twists and turns, the smaller particles cannot keep up with the motion of the air and thus they collide with the fibers. The smallest particles have very little inertia and move randomly as a result of collisions with individual air molecules (Brownian motion). Because of their movement, they end up crashing into the fibers.{{Cite journal|last1=Christopherson|first1=David A.|last2=Yao|first2=William C.|last3=Lu|first3=Mingming|last4=Vijayakumar|first4=R.|last5=Sedaghat|first5=Ahmad R.|date=July 14, 2020|title=High-Efficiency Particulate Air Filters in the Era of COVID-19: Function and Efficacy|journal=Otolaryngology–Head and Neck Surgery|volume=163|issue=6|pages=1153–1155|doi=10.1177/0194599820941838|pmid=32662746|doi-access=free|s2cid=220518635}} Key factors affecting its functions are fiber diameter, filter thickness, and face velocity, which is the measured air speed at an inlet or outlet of a heating ventilation and air conditioning (HVAC) system. Face velocity is measured in m/s and can be calculated as the volume flow rate (m³/s) divided by the face area (m²). The air space between HEPA filter fibers is typically much greater than 0.3 μm. Unlike sieves or membrane filters, where particles smaller than openings or pores can pass through, HEPA filters are designed to target a range of particle sizes. These particles are trapped (they stick to a fiber) through a combination of the following three mechanisms:

1. Diffusion; particles below 0.3 μm are captured by diffusion in a HEPA filter. This mechanism is a result of the collision with gas molecules by the smallest particles, especially those below 0.1 μm in diameter. The small particles are effectively blown or bounced around and collide with the filter media fibers. This behavior is similar to Brownian motion and raises the probability that a particle will be stopped by either interception or impaction; this mechanism becomes dominant at lower airflow.
2. Interception; particles following a line of flow in the air stream come within one radius of a fiber and adhere to it. Mid size particles are being captured by this process.
3. Impaction; larger particles are unable to avoid fibers by following the curving contours of the air stream and are forced to embed in one of them directly; this effect increases with diminishing fiber separation and higher air flow velocity.

Diffusion predominates below the 0.1 μm diameter particle size, whilst impaction and interception predominate above 0.4 μm.{{cite web|last1=Woodford|first1=Chris|author1-link=Chris Woodford (author)|date=May 21, 2008|title=How do HEPA air filters work?|url=https://www.explainthatstuff.com/hepafilters.html|url-status=live|access-date=May 15, 2021|website=Explain That Stuff|archive-date=2020-04-20|archive-url=https://web.archive.org/web/20200420203811/https://www.explainthatstuff.com/hepafilters.html}} In between, near the most penetrating particle size (MPPS) 0.21 μm, both diffusion and interception are comparatively inefficient.{{Cite journal|last=da Roza|first=R. A.|date=December 1, 1982|title=Particle size for greatest penetration of HEPA filters—and their true efficiency.|url=https://www.osti.gov/servlets/purl/6241348-a5wL4J/|url-status=live|access-date=May 15, 2021|website=U.S. Department of Energy Office of Scientific and Technical Information|doi=10.2172/6241348|osti=6241348|doi-access=free|archive-date=May 16, 2021|archive-url=https://web.archive.org/web/20210516175118/https://www.osti.gov/biblio/6241348-a5wL4J/}} Because this is the weakest point in the filter's performance, the HEPA specifications use the retention of particles near this size (0.3 μm) to classify the filter. However it is possible for particles smaller than the MPPS to not have filtering efficiency greater than that of the MPPS. This is due to the fact that these particles can act as nucleation sites for mostly condensation and form particles near the MPPS.

HEPA filters are designed to arrest very fine particles effectively, but they do not filter out gasses and odor molecules. Circumstances requiring filtration of volatile organic compounds, chemical vapors, or cigarette, pet or flatulence odors call for the use of an activated carbon (charcoal) or other type of filter instead of or in addition to a HEPA filter.{{cite journal|last1=Khan|first1=Faisal I|last2=Ghoshal|first2=Aloke Kr.|date=November 2000|title=Removal of Volatile Organic Compounds from polluted air|url=http://beta.chem.uw.edu.pl/people/AMyslinski/nowy/zarzadzanie_01/literature_HWW/02.pdf|journal=Journal of Loss Prevention in the Process Industries|publisher=Elsevier|volume=13|issue=6|pages=527–545|doi=10.1016/S0950-4230(00)00007-3|bibcode=2000JLPPI..13..527K |issn=0950-4230|access-date=May 15, 2021|archive-date=February 15, 2017|archive-url=https://web.archive.org/web/20170215081514/http://www.chem.uw.edu.pl/people/AMyslinski/nowy/zarzadzanie_01/literature_HWW/02.pdf|url-status=live}} Carbon cloth filters, claimed to be many times more efficient than the granular activated carbon form at adsorption of gaseous pollutants, are known as high efficiency gas adsorption filters (HEGA) and were originally developed by the British Armed Forces as a defense against chemical warfare.{{cite journal|last=Glover|first=Norman J.|date=May 2002|title=Countering chemical and biological terrorism|journal=Civil Engineering|location=New York City|publisher=American Society of Civil Engineers|volume=72|issue=5|pages=62–67|issn=0885-7024|oclc=926218714|id={{ProQuest|228557557}}}}{{cite web|last=Jonathan|date=August 19, 2016|title=Air Purifier Acronyms - Stripping Out The Tech Jargon|url=https://www.airenhancing.com/air-purifiers-acronyms-explained/#HEGA_8211_High-Efficiency_Gas_Assistance_or_High-Efficiency_Gas_Absorption_or_High-Efficiency_Gas_Adsorption|url-status=usurped|access-date=May 16, 2021|website=Air Enhancing|archive-date=2020-04-20 |archive-url=https://web.archive.org/web/20200420073627/https://www.airenhancing.com/air-purifiers-acronyms-explained/#HEGA_8211_High-Efficiency_Gas_Assistance_or_High-Efficiency_Gas_Absorption_or_High-Efficiency_Gas_Adsorption}}

A HEPA bag filter can be used in conjunction with a pre-filter (usually carbon-activated) to extend the usage life of the more expensive HEPA filter.{{Cite web|title=Air Purifier Pre-Filter Replacement: The Prefilter Experiments|url=http://www.air-purifier-power.com/replacementprefilter.html|url-status=live|access-date=May 16, 2021|website=Air-Purifier-Power|archive-date=2020-04-20 |archive-url=https://web.archive.org/web/20200420075902/http://www.air-purifier-power.com/replacementprefilter.html}} In such setup, the first stage in the filtration process is made up of a pre-filter which removes most of the larger dust, hair, PM10 and pollen particles from the air. The second stage high-quality HEPA filter removes the finer particles that escape from the pre-filter. This is common in air handling units.{{cn|date=March 2024}}

File:HEPA filter unit.jpg

HEPA filters, as defined by the United States Department of Energy (DOE) standard adopted by most American industries, remove at least 99.97% of aerosols 0.3 micrometers (μm) in diameter.{{Cite web|last=Perryman|first=Oliver|date=December 3, 2020|title=Do HEPA filters or air purifiers remove carbon monoxide?|url=https://dehumidifiercritic.com/do-hepa-filters-remove-carbon-monoxide/|url-status=live|access-date=May 16, 2021|website=Dehumidifier Critic|archive-date=May 16, 2021|archive-url=https://web.archive.org/web/20210516175103/https://dehumidifiercritic.com/do-hepa-filters-remove-carbon-monoxide/}} The filter's minimal resistance to airflow, or pressure drop, is usually specified around {{convert|300|Pa}} at its nominal volumetric flow rate.

The specification used in the European Union: European Standard EN 1822-1:2019, from which ISO 29463 is derived,{{cite web|date=October 15, 2011|title=INTERNATIONAL ISO STANDARD 29463-1—High-efficiency filters and filter media for removing particles in air|url=https://www.sis.se/api/document/preview/913826/|url-status=live|access-date=May 16, 2021|publisher=International Organization for Standardization|archive-date=March 8, 2021|archive-url=https://web.archive.org/web/20210308162337/https://www.sis.se/api/document/preview/913826/}} defines several classes of filters by their retention at the given most penetrating particle size (MPPS): Efficient Particulate Air filters (EPA), High Efficiency Particulate Air filters (HEPA), and Ultra Low Particulate Air filters (ULPA). The averaged efficiency of the filter is called "overall", and the efficiency at a specific point is called "local":

See also the different classes for air filters for comparison.

{{Infobox regulated PPE}}

{{main|NIOSH air filtration rating}}

For respirators, MSHA and NIOSH define HEPA as filters blocking ≥ 99.97% of 0.3 micron DOP particles, under 30 CFR 11 and 42 CFR 84. Since the transition to 42 CFR 84 in 1995, use of the term HEPA has been deprecated except for powered air-purifying respirators.{{cite journal|first1=David|last1=Spelce|first2=Timothy R|last2=Rehak|first3=Richard W|last3=Meltzer|first4=James S|last4=Johnson|date=2019|title=History of U.S. Respirator Approval (Continued) Particulate Respirators|journal=J Int Soc Respir Prot|volume=36 |issue=2 |pages=37–55 |pmid=32572305 |pmc=7307331 }} However, by definition, ANSI Z88.2-2015 considers N100, R100, P100, and HE as HEPA filters.{{citation|url=https://webstore.ansi.org/preview-pages/ASSE/preview_ANSI+ASSE+Z88.2-2015.pdf?srsltid=AfmBOoqcRAVMMGlzi5vb9BRw7GGDyQE8rcp4zLI1iLD9BE8z4rJYSm3e|title=ANSI/ASSE Z88.2 - 2015 American National Standard Practices for Respiratory Protection |date=April 2015}}

Some companies use the marketing term "True HEPA" to give consumers assurance that their air filters meet the HEPA standard, although this term has no legal or scientific meaning.{{cite web|last=Bretag|first=Scott|date=March 18, 2020|title=Air Conditioners, HEPA Filters, And Airborne Allergens|url=https://www.pulseelectrical.com.au/air-conditioners-hepa-filters-and-airborne-allergens/|url-status=live|access-date=May 16, 2021|work=Pulse Electrical|archive-date=March 10, 2021|archive-url=https://web.archive.org/web/20210310161225/https://www.pulseelectrical.com.au/air-conditioners-hepa-filters-and-airborne-allergens/}} Products that are marketed to be "HEPA-type," "HEPA-like," "HEPA-style" or "99% HEPA" do not satisfy the HEPA standard and may not have been tested in independent laboratories. Although such filters may come reasonably close to HEPA standards, others fall significantly short.{{Cite web|title=HEPA-Type Filter: The Great Pretender|url=http://www.air-purifier-power.com/hepatypefilter.html|url-status=live|access-date=May 16, 2021|website=Air-Purifier-Power|archive-date=February 25, 2021|archive-url=https://web.archive.org/web/20210225051425/http://www.air-purifier-power.com/hepatypefilter.html}}

In general terms (and allowing for some variation depending on factors such as the air-flow rate, the physical properties of the particles being filtered, as well as engineering details of the entire filtration-system design and not just the filter-media properties), HEPA filters experience the most difficulty in capturing particles in the size range of 0.15 to 0.2 μm.{{Cite journal |last1=Christopherson |first1=David A. |last2=Yao |first2=William C. |last3=Lu |first3=Mingming |last4=Vijayakumar |first4=R. |last5=Sedaghat |first5=Ahmad R. |date=2020-07-14 |title=High-Efficiency Particulate Air Filters in the Era of COVID-19: Function and Efficacy |journal=Otolaryngology–Head and Neck Surgery |volume=163 |issue=6 |pages=1153–1155 |doi=10.1177/0194599820941838 |issn=0194-5998 |pmid=32662746 |doi-access=free |s2cid=220518635}} HEPA filtration works by mechanical means, unlike ionic and ozone treatment technologies, which use negative ions and ozone gas respectively. So, the likelihood of potential triggering of pulmonary side-effects such as asthma{{Cite web |last=Dunkin |first=Mary Anne |date=2010-04-30 |others=Reviewed by Nayana Ambardekar |title=HEPA Filter Benefits for Allergy Relief |url=https://www.webmd.com/allergies/hepa-filters-for-allergies|url-status=live |access-date=2021-05-16 |website=WebMD |archive-date=2021-03-29|archive-url=https://web.archive.org/web/20210329204924/https://www.webmd.com/allergies/hepa-filters-for-allergies}} and allergies is much lower with HEPA purifiers.{{Cite web |last= |first= |date= |title=How do HEPA Filters Help in Cleaning Indoor Air - Complete Guide |url=http://www.pureairhub.com/guide-hepa-air-purifiers/ |url-status=dead |archive-url=https://web.archive.org/web/20191020213512/http://www.pureairhub.com/guide-hepa-air-purifiers/ |archive-date=2019-10-20 |access-date=2021-05-16 |website=Pure Air Hu}}

To ensure that a HEPA filter is working efficiently, the filters should be inspected and changed at least every six months in commercial settings. In residential settings, and depending on the general ambient air quality, these filters can be changed every two to three years. Failing to change a HEPA filter in a timely fashion will result in it putting stress on the machine or system and not removing particles from the air properly. Additionally, depending on the gasketing materials chosen in the design of the system, a clogged HEPA filter can result in extensive bypassing of airflow around the filter.{{Cite web|last=Kelly|first=Tammy|date=March 14, 2018|title=How Often Should A HEPA Filter Be Changed|url=https://www.janitized.com/how-often-should-a-hepa-filter-be-changed/|url-status=live|access-date=May 16, 2021|website=Janitized|archive-date=March 8, 2021|archive-url=https://web.archive.org/web/20210308145354/https://www.janitized.com/how-often-should-a-hepa-filter-be-changed/}}

{{citations needed section|date=June 2024}}

File:Portable powered HEPA respirator.jpg (PAPR) fitted with a HEPA filter, used to protect from airborne or aerosolised pathogens such as tuberculosis]]

Medical filtration systems use extreme ultraviolet light units that effectively kill bacteria, mold and viruses using panels with an anti-microbial coating to kill off the live bacteria and viruses trapped by the HEPA filter media.{{Citation needed|date=June 2019}}

Some of the best-rated HEPA units have an efficiency rating of 99.995%, which assures a very high level of protection against airborne disease transmission.{{cn|date=March 2024}}

HEPA filters are capable of removing viruses including COVID-19 (particles of 60-140 nanometer diameter) from the air harboring the live virus in the filter.

Extreme ultraviolet light must be incorporated into the air purifier in order to kill airborne pathogens such as viruses like COVID-19, mold & bacteria. As such, hospitals saw a surge in adoption during the pandemic in order to mitigate infection risks.

To combat supply chain and cost issues hindering adoption of HEPA filters during the COVID-19 pandemic, a professor at University of California, Davis, created a simple do-it-yourself air purifier design called crbox(Corsi–Rosenthal Box). It involves arranging 4 HEPA filters in a cubic shape, the bottom being made out of cardboard, sealing the filter sides with tape and adding a fan on top.

In addition, the COVID-19 Pandemic resulted in a surge of new air purifier products from new and established brands such as Dyson or Xiaomi hitting the markets.

File:PHILIPS HEPA H10 air filter for vacuum cleaner.JPG

Many vacuum cleaners also use HEPA filters as part of their filtration systems. This is beneficial for asthma and allergy sufferers, because the HEPA filter traps the fine particles (such as pollen and house dust mite feces) which trigger allergy and asthma symptoms. For a HEPA filter in a vacuum cleaner to be effective, the vacuum cleaner must be designed so that all the air drawn into the machine is expelled through the filter, with none of the air leaking past it. This is often referred to as "Sealed HEPA" or sometimes the more vague "True HEPA". Vacuum cleaners simply labeled "HEPA" may have a HEPA filter, but not all air necessarily passes through it. Finally, vacuum cleaner filters marketed as "HEPA-like" will typically use a filter of a similar construction to HEPA, but without the filtering efficiency. Because of the extra density of a true HEPA filter, HEPA vacuum cleaners require more powerful motors to provide adequate cleaning power.{{cn|date=March 2024}}

Washable filters or reusable filters have proven to be very effective in trapping and keeping Airborne contaminants for millennia. Many washable reusable filters today are cleverly designed

& engineered a substrate that electronically draw material to the substrate & attaching to that substrate, lock into place until washed away. Washable reusable filters meet air quality standards, are cost effective, environmentally friendly, no replacement required & little maintenance VS. true HEPA filters are expensive, with regular replacement damaging to the environment and can Harbor contagions which can breed and multiply within the filter substrate.

A high-quality HEPA filter can trap 99.97% of dust particles that are 0.3 microns in diameter. For comparison, a human hair is about 50 to 150 microns in diameter. So, a true HEPA filter is effectively trapping particles several hundred times smaller than the width of a human hair.{{Cite web|last=Anand|first=Mohit|date=November 23, 2020|title=Understanding the Home Air Purifier Technology in Use Today|url=https://honeywellconnection.com/blog/understanding-the-home-air-purifier-technology-in-use-today/|url-status=live|access-date=May 16, 2021|website=Honeywell Connection|archive-date=May 16, 2021|archive-url=https://web.archive.org/web/20210516175132/https://honeywellconnection.com/blog/understanding-the-home-air-purifier-technology-in-use-today/}} Some manufacturers claim filter standards such as "HEPA 4," without explaining the meaning behind them.{{cn|date=February 2023}} This refers to their Minimum Efficiency Reporting Value (MERV) rating.{{cn|date=February 2023}} These ratings are used to rate the ability of an air cleaner filter to remove dust from the air as it passes through the filter. MERV is a standard used to measure the overall efficiency of a filter. The MERV scale ranges from 1 to 16, and measures a filter's ability to remove particles from 10 to 0.3 micrometer in size. Filters with higher ratings not only remove more particles from the air, but they also remove smaller particles.

File:Display VSON WP6910 (air detector) - pm2,5 at Verona (Borgo Milano) Italy - (particulate pollution, polveri sottili) - 2020 01 30 (hour 22-37) - OUTdoor and INdoor (HEPA H13 filter) - first publication commons.wikimedia.org.webm system: without (OUTdoor) and with filter (INdoor)]]

Heating, ventilation, and air conditioning (HVAC){{Cite dictionary|title=Hvac|publisher=Merriam-Webster|url=https://www.merriam-webster.com/dictionary/HVAC|access-date=May 16, 2021|date=|archive-date=January 15, 2021|archive-url=https://web.archive.org/web/20210115194334/https://www.merriam-webster.com/dictionary/HVAC|url-status=live}} is technology that uses air filters, such as HEPA filters, to remove pollutants from the air either indoors or in vehicles. Pollutants include smoke, viruses, powders, etc., and can originate either outside or inside. HVAC is used to provide environmental comfort and in polluted cities to maintain health.{{citation needed|date=February 2021}}

Modern airliners use HEPA filters to reduce the spread of airborne pathogens in recirculated air. Critics have expressed concern about the effectiveness and state of repair of air filtering systems, since they think that much of the air in an airplane cabin is recirculated. Almost all of the air in a pressurized aircraft is, in fact, brought in from the outside, circulated through the cabin and then exhausted through outflow valves in the rear of the aircraft.{{Cite web|last=Smith|first=Patrick|date=July 22, 2012|title=The truth about cabin air|url=https://askthepilot.com/questionanswers/cabin-air-quality/|url-status=live|access-date=May 16, 2021|website=AskThePilot.com|archive-date=May 6, 2021|archive-url=https://web.archive.org/web/20210506161935/http://askthepilot.com/questionanswers/cabin-air-quality/}} About 40 percent of the cabin's air goes through a HEPA filter and the other 60 percent comes from outside the plane. Certified air filters block and capture 99.97 percent of airborne particles.{{Cite magazine|last=Read|first=Johanna|date=August 28, 2020|title=How clean is the air on planes?|url=https://www.nationalgeographic.com/travel/article/how-clean-is-the-air-on-your-airplane-coronavirus-cvd|magazine=National Geographic|publisher=National Geographic Partners|access-date=May 16, 2021|archive-date=May 6, 2021|archive-url=https://web.archive.org/web/20210506132052/https://www.nationalgeographic.com/travel/article/how-clean-is-the-air-on-your-airplane-coronavirus-cvd|url-status=dead}}

In 2016, it was announced that the Tesla Model X would have the world's first HEPA-grade filter in a Tesla car.{{cite web |date=2016-05-02 |title=Putting the Tesla HEPA Filter and Bioweapon Defense Mode to the Test |url=https://www.tesla.com/blog/putting-tesla-hepa-filter-and-bioweapon-defense-mode-to-the-test |url-status=live |access-date=2021-05-16 |website=Tesla, Inc. |archive-date=2021-04-27 |archive-url=https://web.archive.org/web/20210427150211/https://www.tesla.com/blog/putting-tesla-hepa-filter-and-bioweapon-defense-mode-to-the-test}} Following the release of the Model X, Tesla has updated the Model S to also have an optional HEPA air filter.{{Cite news |last=Völcker |first=John |date=2016-04-12 |title=2016 Tesla Model S gets styling update, 48-amp charger, new interior options, $1,500 price increase (updated) |work=Green Car Reports |url=https://www.greencarreports.com/news/1103380_2016-tesla-model-s-gets-styling-update-48-amp-charger-new-interior-options |access-date=2021-05-16 |archive-date=2021-02-24 |archive-url=https://web.archive.org/web/20210224154947/https://www.greencarreports.com/news/1103380_2016-tesla-model-s-gets-styling-update-48-amp-charger-new-interior-options |url-status=live}}

The idea behind the development of the HEPA filter was born from gas masks worn by soldiers fighting in World War II. A piece of paper found inserted into a German gas mask had a remarkably high capture efficiency for chemical smoke. The British Army Chemical Corps duplicated this and began to manufacture it in large quantities for their own service gas masks. They needed another solution for operational headquarters, where individual gas masks were impractical. The Army Chemical Corps developed a combination mechanical blower and air purifier unit, which incorporated cellulose-asbestos paper in a deeply-pleated form with spacers between the pleats. It was referred to as an "absolute" air filter and laid the groundwork for further research to come in developing the HEPA filter.{{cite journal|last1=First|first1=Melvin W.|date=March 1, 1998|title=HEPA Filters|url=https://www.liebertpub.com/doi/pdf/10.1177/109135059800300111|journal=Journal of the American Biological Safety Association|publisher=American Biological Safety Association|volume=3|issue=1|pages=33–42|doi=10.1177/109135059800300111|issn=1091-3505|s2cid=207941359|access-date=May 16, 2021|archive-date=May 16, 2021|archive-url=https://web.archive.org/web/20210516175101/https://www.liebertpub.com/doi/pdf/10.1177/109135059800300111|url-status=live|url-access=subscription}}

The next phase of the HEPA filter was designed in the 1940s and was used in the Manhattan Project to prevent the spread of airborne radioactive contaminants.{{Cite book|last=|first=|url=https://books.google.com/books?id=XtXJzogLCecC&pg=PA13|title=Green Health: An A-to-Z Guide|date=2011|publisher=SAGE Publishing|isbn=9781412996884|editor-last=Ogunseitan|editor-first=Oladele|location=Los Angeles|pages=13|oclc=793012578|editor-last2=Robbins|editor-first2=Paul|access-date=2016-12-18|archive-date=2021-05-17|archive-url=https://web.archive.org/web/20210517182333/https://books.google.com/books?id=XtXJzogLCecC&pg=PA13|url-status=live}} The US Army Chemical Corps and National Defense Research Committee needed to develop a filter suitable for removing radioactive materials from the air. The Army Chemical Corps asked Nobel Laureate Irving Langmuir to recommend filter test methods and other general recommendations for creating the material to filter out these radioactive particles. He identified 0.3 micron size particles to be the "most penetrating size"—the most difficult and concerning.{{cite web|date=November 21, 2019|title=The History of HEPA Filters|url=https://www.apcfilters.com/the-history-of-hepa-filters/|url-status=live|access-date=May 16, 2021|website=APC Filters|archive-date=March 26, 2021|archive-url=https://web.archive.org/web/20210326084208/https://www.apcfilters.com/the-history-of-hepa-filters/}}

It was commercialized in the 1950s, and the original term became a registered trademark and later a generic trademark for highly efficient filters.{{Cite book|url=https://books.google.com/books?id=QSNfCrpcSCAC&q=HEPA+filter+registered+trademark&pg=PA128|title=The Vacuum Cleaner: A History|last=Gantz|first=Carroll|date=2012-09-21|publisher=McFarland|isbn=9780786493210|page=128|language=en|access-date=2020-11-11|archive-date=2021-05-16|archive-url=https://web.archive.org/web/20210516175103/https://books.google.com/books?id=QSNfCrpcSCAC&q=HEPA+filter+registered+trademark&pg=PA128|url-status=live}}

Over the decades filters have evolved to satisfy the higher and higher demands for air quality in various high technology industries, such as aerospace, pharmaceutical industry, hospitals, health care, nuclear fuels, nuclear power, and integrated circuit fabrication.{{cn|date=March 2024}}

• {{annotated link|Air purifier}}
• {{annotated link|Clean air delivery rate}}
• {{annotated link|Cleanroom}}
• {{annotated link|Electrostatic precipitator}} – trap particles with high voltage
• {{annotated link|Hypoallergenic vacuum cleaner}} – vacuum cleaner with high efficiency air filter
• {{annotated link|Minimum efficiency reporting value}} (MERV)
• {{annotated link|Respirator}}
• {{annotated link|ULPA}} – Removes 99.999% of dust, pollen, mold, bacteria, and particles larger than 120 nm (0.12 μm)
• {{annotated link|Ultraviolet germicidal irradiation}}
• {{annotated link|Corsi–Rosenthal Box}}

{{reflist|30em}}

• [https://web.archive.org/web/20170829125133/http://www.tsi.com/uploadedFiles/Product_Information/Literature/Application_Notes/ITI-041.pdf TSI Application Note ITI-041: Mechanisms of Filtration for High Efficiency Fibrous Filters]

{{commons category|High-Efficiency Particulate Arresting}}

{{HVAC}}

{{DEFAULTSORT:Hepa}}

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