What is the best air filter for pet allergies
- ^European Standard EN , «High efficiency air filters (EPA, HEPA and ULPA)»,
- ^ abGantz, Carroll (). The Vacuum Cleaner: A History. McFarland. p. ISBN.
- ^Ryback, Emily (12 August ). «Guide to HEPA Air Purifiers». Pure Air Hub. Kurt Morgan.
- ^Khan, Faisal I; Kr. Ghoshal, Aloke (November ). «Removal of Volatile Organic Compounds from polluted air»(PDF).
Journal of Loss Prevention in the Process Industries. 13 (6): – doi/S(00) Retrieved 30 July
- ^«How Often Should A HEPA Filter Be Changed | Janitized». Janitized Vacuum Cleaner Bag Manufacturer. Retrieved
- ^HEPA Company glossary of terms
- ^Glover, N. J. (). «Countering chemical and biological terrorism». Civil Engineering. 72 (5):
- ^«Air Purifier Acronyms – Stripping Out The Tech Jargon». AirEnhancing.
- ^«HEPA Air Filtration System for Home & Office — Types of HEPA Filter».
- ^«About HEPA». . Retrieved
- ^American Society of Mechanical Engineers, ASME AG-1a–, «Addenda to ASME AG-1– Code on Nuclear Air and Gas Treatment»,
- ^«HEPA Filter Benefits for Allergy Relief». Retrieved
- ^John Voelcker (12 April ). » Tesla Model S gets styling update, amp charger, new interior options, $1, price increase (updated)». Green Car Reports. Retrieved 14 April
- ^«HEPA-type filter: The Grand Pretender». . Retrieved
- ^Originally ‘High Efficiency Particulate Arrestment — see
- ^Gupta ().
Modern Trends in Planning and Designing of Hospitals: Principles and Practice. Jaypee Brothers Medical Publishers (P) Ltd. p. ISBN.
- ^ abWoodford, Chris.
«HEPA Filters». Explain That Stuff.
Retrieved 30 July
- ^Ogunseitan, Oladele (). Green Health: An A-to-Z Guide. SAGE.
- ^First, Melvin W. (). «HEPA Filters». Journal of the American Biological Safety Association. 3 (1): Retrieved 9 December
- ^«Efficiency of the HEPA air filter: HEPA filter quality and bypassing». . Retrieved
- ^«Air Purifier Pre-Filter Replacement: The Prefilter Experiments». . Retrieved
- ^«Should A True HEPA Filter Mean Anything To You?». . Archived from the original on 3 March Retrieved 25 March
- ^«Putting the Tesla HEPA Filter and Bioweapon Defense Mode to the Test». Tesla Canada. Retrieved 19 November
- ^ abBarnette, Sonya.
«Specification for HEPA Filters Used by DOE Contractors — DOE Technical Standards Program». . Retrieved
- ^ abRoza, R. A. (), Particle size for greatest penetration of HEPA filters — and their true efficiency, California: Lawrence Livermore National Laboratory, OSTI,
- ^«The History of HEPA Filters». APC Filtration Inc. Retrieved 9 December
HEPA filters are composed of a mat of randomly arranged fibres. The fibers are typically composed of fiberglass and possess diameters between and micrometers.
Key factors affecting its functions are fiber diameter, filter thickness, and face velocity. The air space between HEPA filter fibers is typically much greater than μm. The common assumption[by whom?] that a HEPA filter acts love a sieve where particles smaller than the largest opening can pass through is incorrect and impractical. Unlike membrane filters at this pore size, where particles as wide as the largest opening or distance between fibers can not pass in between them at every, HEPA filters are designed to target much smaller pollutants and particles.
These particles are trapped (they stick to a fiber) through a combination of the following three mechanisms:
- An enhancing mechanism that is a result of the collision with gas molecules by the smallest particles, especially those under μm in diameter, which are thereby impeded and delayed in their path through the filter; 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 air flow
- Particles following a line of flow in the air stream come within one radius of a fiber and adhere to it.
- 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 under the μm diameter particle size, whilst impaction and interception predominate above μm. In between, near the most penetrating particle size (MPPS) μm, both diffusion and interception are comparatively inefficient. Because this is the weakest point in the filter’s performance, the HEPA specifications use the retention of particles near this size (μm) to classify the filter. However it is possible for particles smaller than the MPPS to not own 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 extremely fine particles effectively, but they do not filter out gasses and odor molecules. Circumstances requiring filtration of volatile organic compounds, chemical vapors, cigarette, pet, and/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. Carbon cloth filters, claimed to be numerous times more efficient than the granular activated carbon form at adsorption of gaseous pollutants, are known as HEGA filters («High Efficiency Gas Adsorption») and were originally developed by the British military as a defense against chemical warfare.
Pre-filter and HEPA Filter
A HEPA filter can be used in conjunction with a pre-filter (usually carbon-activated) to extend the usage life of the more expensive HEPA filter. 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, which filters out the finer particles that escapes from the pre-filter.
HEPA filters, as defined by the United States Department of Energy (DOE) standard adopted by most American industries, remove at least % of airborne particles micrometers (μm) in diameter. The filter’s minimal resistance to airflow, or pressure drop, is generally specified around pascals (psi) at its nominal volumetric flow rate.
The specification used in the European Union: European Standard EN , defines several classes of HEPA filters by their retention at the given most penetrating particle size (MPPS):
|HEPA class||Retention (total)||Retention (local)|
|H13||> %||> %|
|H14||> %||> %|
|U15||> %||> %|
|U16||> %||> %|
|U17||> %||> %|
See also the diverse classes for air filters for comparison.
Today, a HEPA filter rating is applicable to any highly efficient air filter that can attain the same filter efficiency performance standards as a minimum and is equivalent to the more recent National Institute for Occupational Safety and Health N rating for respirator filters. The United States Department of Energy (DOE) has specific requirements for HEPA filters in DOE-regulated applications.
Some companies use a marketing term known as «True HEPA» to give consumers assurance that their air filters meet the HEPA standard, although this term has no legal or scientific meaning. Products that are marketed to be «HEPA-type,» «HEPA-like,» «HEPA-style» or «99% HEPA» do not satisfy the HEPA standard and may not own been tested in independent laboratories.
Although such filters may come reasonably shut to HEPA standards, others drop significantly short.
HEPA filters are critical in the prevention of the spread of airborne bacterial and viral organisms and, therefore, infection. Typically, medical use HEPA filtration systems also incorporate high-energy ultra-violet light units or panels with anti-microbial coating to kill off the live bacteria and viruses trapped by the filter media. Some of the best-rated HEPA units own an efficiency rating of %, which assures a extremely high level of protection against airborne disease transmission.
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 dust mitefeces) 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 own a HEPA filter, but not every 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 additional density of a true HEPA filter, HEPA vacuum cleaners require more powerful motors to provide adequate cleaning power.
Some newer models claim to be better than the earlier ones with the inclusion of «washable» filters.
Generally, washable true HEPA filters are expensive. A high-quality HEPA filter that can trap % of dust particles that are microns in diameter. For comparisons sake, a human hair is about 50 to microns in diameter. So, a true HEPA filter is effectively trapping particles several hundred time smaller than the width of a human hair. Some manufacturers claim filter standards such as «HEPA 4,» without explaining the meaning behind them.
This refers to their Minimum Efficiency Reporting Worth (MERV) rating. 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 20, and measures a filter’s ability to remove particles from 10 to micrometer in size. Filters with higher ratings not only remove more particles from the air, they also remove smaller particles.
Modern airliners use HEPA filters to reduce the spread of airborne pathogens in recirculated air. Critics own expressed concern about the effectiveness and state of repair of air filtering systems, since they ponder that much of the air in an airplane cabin is recirculated. Almost every of the air in a pressurized aircraft is, in fact, brought in from the exterior, circulated through the cabin and then exhausted through outflow valves in the rear of the aircraft.
Some cars own cabin air filters that glance love HEPA filters but which do not act out at that level.
The confusion is perpetuated by guides[example needed] for changing car filters which misidentify[according to whom?] the filters as HEPA filters. The actual performance of these filters is obscured[where?] by manufacturers[example needed] and hard to evaluate,[according to whom?] as they are not rated with the MERV system, though they typically[clarification needed] yield MERV 8-equivalent performance.
In , the Tesla Model X was announced to own the world’s first HEPA-grade filter. Following the release of the Model X, Tesla has updated the Model S to also own an optional HEPA air filter.
HEPA filtration works by mechanical means unlike the ionic and ozone filtration which use negative ions and ozone gas respectively.
So, the chances of potential pulmonary side-effects love asthma and allergies is much lower with HEPA purifiers. To ensure that a HEPA filter is working efficiently, they should be checked and changed at least every six months in commercial settings. In residential settings, they 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.
This section needs expansion.
You can assist by adding to it.(December )
The thought 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.
The next phase of the HEPA filter was designed in the s and was used in the Manhattan Project to prevent the spread of airborne radioactive contaminants. 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 micron size particles to be the «most penetrating size» — the most hard and concerning.
It was commercialized in the s, and the original term became a registered trademark and later a generic term for highly efficient filters.
Over the decades filters own evolved to satisfy the higher and higher demands for air quality in various high technology industries, such as aerospace, pharmaceutical drug processing, hospitals, health care, nuclear fuels, nuclear power, and integrated circuit fabrication.