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An air ioniser (or negative ion generator or Chizhevsky's chandelier) is a device that uses high voltage to
ionise Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...
(electrically charge)
air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...
molecules. Negative ions, or
anions An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by con ...
, are particles with one or more extra electrons, conferring a net negative charge to the particle.
Cations An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
are positive ions missing one or more electrons, resulting in a net positive charge. Some commercial air purifiers are designed to generate negative ions. Another type of air ioniser is the electrostatic discharge (ESD) ioniser (balanced ion generator) used to neutralise static charge.


History

In 1918
Alexander Chizhevsky Alexander Leonidovich Chizhevsky (russian: Алекса́ндр Леони́дович Чиже́вский, also Aleksandr Leonidovich Tchijevsky) (7 February 1897 – 20 December 1964) was a Soviet-era interdisciplinary scientist, a biophysicist ...
had created the first air ioniser for ion therapy.Pat Williams Obituary of Coppy Laws, Independent newspaper, London, England, 4 June 2002 It was originally used for animal health in agriculture. This discovery ignited
Cecil Alfred 'Coppy' Laws Cecil Alfred "Coppy" Laws (21 November 1916 – 28 May 2002) was a British electronic engineer and radar engineer during World War II, and the inventor of the domestic air ioniser or ionizer. Life C A Coppy Laws was born in Great Yarmouth on 2 ...
' interest in the little-known phenomenon of air ionisation. In 2002, in an obituary in '' The Independent'' newspaper,
Cecil Alfred 'Coppy' Laws Cecil Alfred "Coppy" Laws (21 November 1916 – 28 May 2002) was a British electronic engineer and radar engineer during World War II, and the inventor of the domestic air ioniser or ionizer. Life C A Coppy Laws was born in Great Yarmouth on 2 ...
was credited with being the inventor of the domestic air ioniser.


Ionic air purifiers

Air ionisers are used in
air purifier An air purifier or air cleaner is a device which removes contaminants from the air in a room to improve indoor air quality. These devices are commonly marketed as being beneficial to allergy sufferers and asthmatics, and at reducing or eliminating ...
s to remove particles from air. Airborne particles become charged as they attract charged ions from the ioniser by electrostatic attraction. The particles in turn are then attracted to any nearby earthed (grounded) conductors, either deliberate plates within an air cleaner, or simply the nearest walls and ceilings. The frequency of
nosocomial infection A hospital-acquired infection, also known as a nosocomial infection (from the Greek , meaning "hospital"), is an infection that is acquired in a hospital or other health care facility. To emphasize both hospital and nonhospital settings, it is so ...
s in British hospitals prompted the National Health Service (NHS) to research the effectiveness of anions for air purification, finding that repeated airborne ''
acinetobacter ''Acinetobacter'' is a genus of gram-negative bacteria belonging to the wider class of Gammaproteobacteria. ''Acinetobacter'' species are oxidase-negative, exhibit twitching motility, and occur in pairs under magnification. They are important ...
'' infections in a ward were eliminated by the installation of a negative air ioniser—the infection rate fell to zero, an unexpected result. Positive and negative ions produced by air conditioning systems have also been found by a manufacturer to inactivate viruses including influenza. A 2018 review found that negative air ions are highly effective in removing
particulate matter Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The te ...
from air. The SARS epidemic fuelled the desire for personal ionisers in East Asia, including Japan (where many products have been specialised to contain negative ion generators, including
toothbrush A toothbrush is an oral hygiene tool used to clean the teeth, gums, and tongue. It consists of a head of tightly clustered bristles, atop of which toothpaste can be applied, mounted on a handle which facilitates the cleaning of hard-to-reach a ...
es,
refrigerator A refrigerator, colloquially fridge, is a commercial and home appliance consisting of a thermally insulated compartment and a heat pump (mechanical, electronic or chemical) that transfers heat from its inside to its external environment so t ...
s, air conditioners, air cleaners, and washing machines). There are no specific standards for these devices. There are two types of ionic air purifiers, the fanless and fan base ionizers. The fan base ionizer uses its fan to circulate air around the room rapidly, but it is noisier and consumes more energy, while the fanless types distribute air slowly, taking a longer time to purify air, but are noiseless and more energy efficient.


California regulation of ozone produced by air cleaners and ionizers

The
California Air Resources Board The California Air Resources Board (CARB or ARB) is the "clean air agency" of the government of California. Established in 1967 when then-governor Ronald Reagan signed the Mulford-Carrell Act, combining the Bureau of Air Sanitation and the Moto ...
has a page listing air cleaners (many with ionizers) meeting their indoor ozone limit of 0.050 parts per million. From that article:


Ions versus ozone

Ionisers are distinct from
ozone generator Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lower ...
s, although both devices operate in a similar way. Ionisers use electrostatically charged plates to produce positively or negatively charged gas ions (for instance N2 or O2) that particulate matter sticks to in an effect similar to
static electricity Static electricity is an imbalance of electric charges within or on the surface of a material or between materials. The charge remains until it is able to move away by means of an electric current or electrical discharge. Static electricity is na ...
. Even the best ionisers will also produce a small amount of ozone—triatomic oxygen, O3—which is unwanted. Ozone generators are optimised to attract an extra oxygen ion to an O2 molecule, using either a corona discharge tube or UV light. At concentrations that do not exceed public health standards, ozone has been found to have little potential to remove indoor air contaminants. At high concentrations ozone can be
toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...
to air-borne bacteria, and may destroy or kill these sometimes infectious organisms. However, the required concentrations are sufficiently toxic to humans and animals that the US FDA declares that ozone has no place in medical treatment and has taken action against businesses that violate this regulation by offering therapeutic ozone generators or
ozone therapy Ozone therapy is an alternative medical treatment that introduces ozone or ozonides to the body. The United States Food and Drug Administration (FDA) prohibits all medical uses of ozone, "In any medical condition for which there is no proof of s ...
. Ozone is a highly toxic and extremely reactive gas. A higher daily average than 0.1 ppm (100 ppb, 0.2 mg/m3) is not recommended and can damage the lungs and
olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OF ...
cells directly.


Health effects

A 2013 comprehensive review of 80 years of research into air ions and respiratory function outcomes found that there was no clear support for any beneficial role in respiratory function, nor evidence for significant detrimental effect. In conclusion, "exposure to negative or positive air ions does not appear to play an appreciable role in respiratory function." There is weak evidence that negative air ionization is associated with lower depression scores, particularly at the highest exposure level. No consistent influence of positive or negative air ionization on anxiety, mood, relaxation, sleep, and personal comfort measures was observed.


Adverse health effects of ozone byproduct

Studies have been carried out on negative ion generators. One study shows that the ozone generated can exceed guidelines in small, non ventilated areas. Another study showed that ozone can react with other constituents, namely cleaning agents to increase pollutants such as formaldehyde (this study had as its objective the testing of the use of cleaning products and air fresheners indoors and associated health risks as opposed to adverse health effects of air ionisers).


''Consumer Reports'' court case

''
Consumer Reports Consumer Reports (CR), formerly Consumers Union (CU), is an American nonprofit consumer organization dedicated to independent product testing, investigative journalism, consumer-oriented research, public education, and consumer advocacy. Founde ...
'', a non-profit U.S.-based product-testing magazine, reported in October 2003 that air ionisers do not perform to high enough standards compared to conventional HEPA filters. The exception was a combination unit that used a fan to move air while ionizing it. In response to this report,
The Sharper Image Sharper Image is an American brand that offers consumers home electronics, air purifiers, gifts, and other high-tech lifestyle products through its website, catalog, and third-party retailers. The brand is owned by ThreeSixty Group, with the U.S. ...
, a manufacturer of air ionisers (among other products), sued Consumer's Union (the publishers of ''Consumer Reports'') for product defamation. ''Consumer Reports'' gave the Ionic Breeze and other popular units a "fail" because they have a low clean air delivery rate (CADR). CADR measures the amount of filtered air circulated during a short period of time, and was originally designed to rate media-based air cleaners. The Sharper Image claimed that this test was a poor way to rate the Ionic Breeze, since it does not take into account other features, such as 24-hour-a-day continuous cleaning, ease of maintenance, and silent operation. The
United States District Court for the Northern District of California The United States District Court for the Northern District of California (in case citations, N.D. Cal.) is the federal United States district court whose jurisdiction comprises the following counties of California: Alameda, Contra Costa, De ...
dismissed the case, reasoning that the Sharper Image had failed to demonstrate that it could prove any of the statements made by ''Consumer Reports'' were false. The court's final ruling in May 2005 ordered the Sharper Image to pay US$525,000 for Consumer Union's legal expenses.


Electrostatic neutraliser in electronics

Air ionisers are often used in places where work is done involving static-electricity-sensitive electronic components (like in microelectronics
cleanroom A cleanroom or clean room is an engineered space, which maintains a very low concentration of airborne particulates. It is well isolated, well-controlled from contamination, and actively cleansed. Such rooms are commonly needed for scientif ...
s), to eliminate the build-up of static
charges Charge or charged may refer to: Arts, entertainment, and media Films * ''Charge, Zero Emissions/Maximum Speed'', a 2011 documentary Music * ''Charge'' (David Ford album) * ''Charge'' (Machel Montano album) * '' Charge!!'', an album by The Aqu ...
on non-conductors. As those elements are very sensitive to electricity, they cannot be grounded because the discharge will destroy them as well. Usually, the work is done over a special dissipative table mat, which allows a very slow discharge, and under the air gush of an ioniser. The ionization falls off very sharply with distance (even in ducting), so air ionization is rarely used for this purpose, and only for items immediately adjacent to the actual ionizer.


See also

* Dehumidifier *
Electrostatic precipitator An electrostatic precipitator (ESP) is a filterless device that removes fine particles, like dust and smoke, from a flowing gas using the force of an induced electrostatic charge minimally impeding the flow of gases through the unit. In con ...
* Humidifier *
Nebulizer In medicine, a nebulizer (American English) or nebuliser (British English) is a drug delivery device used to administer medication in the form of a mist inhaled into the lungs. Nebulizers are commonly used for the treatment of asthma, cystic fibr ...
*
Negative air ionization therapy Negative air ionization therapy (NAIs) uses air ionisers as a non-pharmaceutical treatment for respiratory disease, allergy, or stress-related health conditions. The mainstream scientific community considers many applications of NAIs to be pseudo ...


References


Further reading

*


External links


Ionic Air Purifiers and SmogDo "corona discharge" devices alleviate asthma?
{{DEFAULTSORT:Air Ioniser Home appliances Medical equipment Soviet inventions 20th-century inventions