An electronic cigarette, or e-cigarette, is an electrical device that simulates the act of tobacco smoking by producing an inhaled mist bearing the physical sensation, appearance, and often the flavor and nicotine content of inhaled tobacco smoke but without the odor of tobacco smoke. The device uses heat, or in some cases ultrasonics, to vaporize a propylene glycol- or glycerin-based liquid solution into an aerosol mist, similar to the way a nebulizer or humidifier vaporizes solutions for inhalation.
The primary stated use of the electronic cigarette is as a smoking cessation device, as it attempts to deliver the experience of smoking without, or with greatly reduced, adverse health effects usually associated with tobacco smoke. Nevertheless, concerns have been raised that use of the device still carries health risks, and that it could appeal to non-smokers, especially children, due to its novelty, flavorings, and possibly overstated claims of safety.
The possible benefits or adverse effects of electronic cigarette use are a subject of disagreement among different health organizations and researchers. Controlled studies of electronic cigarettes are scarce due to their relatively recent invention and subsequent rapid growth in popularity. Laws governing the use and sale of electronic cigarettes, as well as the accompanying liquid solutions, currently vary widely, with pending legislation and ongoing debate in many regions.
The electronic cigarette was invented by Chinese pharmacist Hon Lik in 2003 and introduced to the market the following year. The company he worked for, Golden Dragon Holdings, changed its name to Ruyan (meaning "to resemble smoking"), and started exporting its products in 2005–2006, before receiving the first international patent in 2007.
Electronic cigarettes generally consist of three primary components: a cartridge, an atomizer, and a battery unit. Some designs implement a disposable integrated cartridge/atomizer component known as a cartomizer.
Most reusable electronic cigarette models are manufactured according to some standard for their connections, making their components interchangeable. The current (June 2011) dominating attachment standards are the 510 and 808D; most components available are made to fit one of these models.
The cartridge is a small, usually disposable, plastic container with openings on each end. It generally houses an absorbent, sponge-like material saturated with the liquid solution to be vaporized. The mouthpiece is constructed so that the vapor produced can flow past the solution container to reach the user's mouth.
When the liquid in the cartridge has been depleted, the user can generally choose between refilling it, or replacing it with another pre-filled cartridge.
Some users forgo the use of cartridges and "drip" liquid directly onto the atomizer, in a method that has aptly come to be known as "dripping". Some manufacturers have responded to this practice by creating special mouthpieces that are intended primarily to ease use by the dripping method.
The atomizer is a heating element that serves to vaporize the solution so it can be inhaled. It contains a filament whose efficiency degrades over time due to a buildup of sediment, or "burns out" entirely, requiring replacement. This creates one of the primary recurring expenses associated with electronic cigarettes.
To deal with atomizer degradation and the associated expense, manufacturers introduced an integrated cartridge/atomizer component that is more cheaply produced, known as a cartomizer. They are generally sold in packages of five or more. When their heating elements degrade, they can be disposed of and replaced more cheaply than standalone atomizers.
Power source and electronics
Most electronic cigarettes are powered by a lithium-ion rechargeable battery. The housing for the battery and electronic circuitry is usually the largest component of an electronic cigarette. This unit may contain an electronic airflow sensor for automated operation, or a button for manual operation. A timed cutoff switch (to prevent overheating) and/or a colored LED may also be included here.
To recharge their batteries, many different types of battery chargers – such as AC outlet, car, and USB – are usually available. Some manufacturers also offer a "Portable Charging Case," or "PCC",which contains a large rechargeable battery that is then used to charge a smaller battery within the individual e-cigarettes.
Another power option is direct USB power, which is available for most electronic cigarette models. A USB-tethered module is attached to the cigarette in place of a battery, and must be plugged into a computer's USB port or a USB AC adapter in order to operate.
Liquids used to produce vapor in electronic cigarettes are widely sold separately for use in refillable cartridges. Liquid is commonly known as "nicotine solution" when it contains the actual nicotine component. Liquids are also sometimes referred to as "e-liquid", "e-juice", etc. in keeping with the "e-" nomenclature. Liquids commonly contain some amount of flavoring, with hundreds of different flavors available. Some flavor varieties attempt to resemble traditional cigarette types, such as regular tobacco and menthol, and some even attempt to mimic specific cigarette brands, such as Marlboro or Camel. Fruit and other flavors, such as chocolate, vanilla, caramel, coffee, and cola, are also available.
Liquid solution consists of flavoring and/or nicotine dissolved in one or several hygroscopic components, which turns the water in the solution into the smoke-like vapour when heated. The most commonly used hygroscopic components are propylene glycol, vegetable glycerin or polyethylene glycol 400, usually referred to as PG, VG and PEG 400 respectively. All three are common food additives and used in a variety of pharmaceutical formulations. Since concerns have been raised by various opponent groups regarding the safety of inhaling these substances, it has been pointed out by proponents that PG has been used as an additive in asthma inhalers and nebulizers since the 1950s, with no serious adverse side effects, and because of its water-retaining properties, is the compound of choice for delivering atomized medication. The U.S. Food and Drug Administration (FDA) includes propylene glycol on its list of substances Generally Recognized as Safe (GRAS), and it meets the requirements of acceptable compounds within Title 21 of the Code of Federal Regulations.
Liquid solutions containing nicotine are available in differing nicotine concentrations to suit user preferences. Concentrations range from zero nicotine, to low/midrange doses (6–8 mg/ml and 10–14 mg/ml respectively), to high and extra-high doses (16–18 mg/ml and 24–36 mg/ml respectively). Nicotine concentration ratings are often printed on the liquid container or cartridge (the standard notation "mg/ml" is often abbreviated simply as "mg").
From : http://en.wikipedia.org/wiki/E-cigarettes
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