Air ioniser
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An air ionizer is a device which ionises, or electrically charges, the air it intakes to give it a positive charge. Such devices are often sold as air purifiers. The ionization of diatomic oxygen often results in the formation of ozone.
Ionic air purifiers
([Disputed statementdisputed]—see [ions from diatomic elements such as oxygen and nitrogen, which constitute airIonisers should not be confused with ozone generators, even though both devices operate in a similar way. Ionisers are optimised to produce negative ions of gaseous molecules, and ozone generators are optimised to produce ozone, though even the best ionisers will produce a small amount of ozone, and ozone generators will produce gaseous ions of molecules other than ozone (unless fed by pure oxygen, not air).#redirect [[Template:Fact]]
Environmental ozone generators use a high negative voltage to produce small amounts of ozone, which, while toxic, is claimed by some alternative medicine proponents to be relatively harmless to humans. This is a demonstrable fallacy, as ozone is a highly toxic and extremely reactive gas.#redirect [[Template:Fact]] Low level ozone exposure is relatively harmless (and natural), but if the ozone levels rise to a level that can be smelled, then as a rule of thumb the concentration is too high. A higher daily average than 0.1 ppm (0.2 mg/m3)is not recommended and can damage the lungs and olfactory bulb cells directly.#redirect [[Template:Fact]] The ozone generated is also highly toxic to air-borne bacteria, and may destroy or kill these sometimes infectious organisms when they come into close contact with the generated ozone. Ozone therapy is illegal in the USA, because the FDA has not approved its use on humans.#redirect [[Template:Fact]]
An air ioniser also generates negative ions by exposing air to a high negative voltage. Negative ions occur naturally near waterfalls and after heavy thunderstorms and are claimed to produce a feeling of increased well-being, and this is the effect that ionisers try to duplicate.#redirect [[Template:Fact]] Conversely, positive ions in the air are claimed by some to produce a feeling of decreased well-being, and such positive ions can be found immediately before thunderstorms and around the high positive voltages on the anodes of cathode ray tubes in TVs and computer monitors. Many ionisers are sold as air purifiers, but in this regard they are very inefficient. They will clean the air to a small degree, by charging dust and smoke particles which will then be attracted to a neutral or positively charged surface. Heavier combined particles may precipitate (fall) out of the air should two smaller particles of different charge clump together. The drawback with using ionisers as air purifiers is that all the affected airborne particles ultimately wind up on surfaces close to the ioniser, including the ioniser and high voltage emitter, reducing the efficiency of the latter as it is slowly covered in dirt, and making the area around the ioniser increasingly dirty also. The static charge on the front of a powered-up TV screen would have similar effect as an air purifier.
The use of negative ions continues to be a more accepted mainstream therapy in Eastern Europe and the Far East than in Western Europe or the United States, although problems with nosocomial infections (hospital acquired "super-bugs") have led the National Health Service (NHS) in the UK to do extensive research into the effect of negative ions on this area of hygiene. The results were very positive (see this article in The New Scientist [link] ). Recent SARS outbreaks have fueled the desire for personal ionisers in the far east, and in Japan everything from toothbrushes to fridges and washing machines have negative ion generators in them. There are no specific standards for these devices, and though a few may have some benefit, most will be at best useless, at worst harmful.
Consumer Reports, 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 air filters. In response to this report, The Sharper Image, a manufacturer of air ionisers (among other things), sued Consumer's Union (the publishers of Consumer Reports) for product defamation. The U.S. District Court for the Northern District of California subsequently struck The Sharper Image's complaint and 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 $525,000 for Consumer Union's legal expenses. [link]
The Sharper Image unit, however, did meet all demands required by the EPA or Environmental Protection Agency. These included the very stringent 50 parts per billion ozone bi-product production. Consumer Reports failed The Sharper Image Ionic Breeze, as well as many other popular units, because they felt that the government ozone limitations were set too high. However, Consumer Reports was protected under their First Amendment rights.#redirect [[Template:Fact]]
Industrial use
Air ionisers, more generally know as electrostatic precipitators, are used industrially as air filters. They are also used to remove dust from products prior to painting.See also
External links
- [New Scientist - Air ionisers wipe out hospital infections]
- [Do "corona discharge" devices alleviate asthma?]
- [Overview of electrofilter precipitator]
- [NIOSH Immediate Danger to Life or Health (Ozone) Documentation]
- [Ionic Air Purifiers and Smog]
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