How do eCigarettes create vapour that mimics tobacco smoke and are they harmful?

Battery-powered cigarettes convert
dissolved nicotine concentrate into
vapour, which can then be inhaled
without many of the toxic by-products
associated with burning tobacco.
The electronic cigarette has three basic
components: a chamber, an atomiser and a
battery. The chamber contains nicotine and
fl avourings in a carrier liquid, such as
propylene glycol. A wick, made from metal
mesh or silica, draws the liquid into the
atomiser, where it is heated by a batterypowered
coil until it vaporises. The vapour is
then inhaled and exhaled like tobacco smoke.
Electronic cigarettes are designed to simulate
the feel, taste and nicotine hit of cigarettes, but
their safety is debated. In many countries their
manufacture and sale is unregulated, resulting
in variation in their chemical contents. Their
usefulness as nicotine replacement therapy is
also largely unknown and the World Health
Organization does not condone their use.