Electronic cigarettes are battery-powered smoking devices often designed to look and feel like regular cigarettes. They use cartridges filled with a liquid that contains nicotine, flavorings, and other chemicals. A heating device in the e-cigarette converts the liquid into a vapor, which the person inhales.
Safety of electronic cigarettes. ... A systematic review suggests that e-cigarettes are less harmful than smoking and since they contain no tobacco and do not involve combustion, users may avoid several harmful constituents usually found in tobacco smoke. However, e-cigarettes cannot be considered harmless.