Reviews that do not agree with Cheng Electronic cigarettes e cigarettes provide nicotine via a vapour that is drawn into the mouth upper airways and possibly lungs 2 3 Brown et al 2014 Drawing air through the e cigarette triggers the heater to create vapour which contains nicotine and is inhaled Public Health England 2014 powered by a lithium ion rechargeable battery that is designed to vaporize nicotine to be inhaled Caponnetto et al 2012 work by vaporizing a solution containing nicotine dissolved with flavorants in a carrier medium usually propylene glycol O Connor 2012 They are battery operated devices used to vaporise a liquid that may or may not contain nicotine Farsalinos et al 2014 I can find loads more So relying entirely on Cheng is not acceptable