Doug the Chimp smoking a cigarette. (Photo by Joseph Scherschel//Time Life Pictures/Getty Images). The location of this image is United States. Copyright: Time & Life Pictures

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 flavour and nicotine content of inhaled tobacco smoke; though without its odour, and intended to omit its health risks. The device uses heat (or in some cases, ultrasonics ) to vaporise a propylene glycol - or glycerine -based liquid solution into an aerosol mist, similar to the way a nebulizer or humidifier vaporises solutions for inhalation.
Most electronic cigarettes are portable, self-contained cylindrical devices the size of a cigarette; though sizes vary, mainly due to differing battery capacities. Many electronic cigarettes are designed to resemble actual cigarettes or cigars , or even pipes . Most are also reusable, with replaceable and refillable parts, but some models are disposable .
The primary stated use of the electronic cigarette is an alternative to tobacco smoking, or 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.
The possible benefits or adverse effects of electronic cigarette use are a subject of disagreement among different health organisations 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. Concerns have been raised that use of the device still might carry health risks, and that it could appeal to non-smokers, especially children, due to its novelty, flavourings, and possibly overstated claims of safety.
The modern electronic cigarette's design was devised by Chinese pharmacist Hon Lik in 2003, though the earliest known description of its concept was authored by Herbert A. Gilbert in 1963.

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