Electronic cigarettes, generally known as electronic vaporizers or e-cigarettes, are electronic devices that vaporize a liquid solution without any combustion to produce a flavoured vapour with appearance, sensation and optional flavor of regular tobacco cigarettes. The resulting vapor does not contain any tar, carbon monoxide, cyanide, nor any of the other harmful chemicals normally present in ordinary tobacco cigarettes, hookahs and cigars.
However, be sure that the establishment doesn’t have their own by-law in place (ie. the Toronto Transit Commision allows the use of vaporizers on TTC property but not on their vehicles or within their buildings.) Do your research.