Unlike cigarettes, e-cigs involve no combustion, but rather, vaporisation. Contrary to cigarettes, there is no combustion in e-cigs, but rather, vaporisation.
In an atomizer, the e-liquid is absorbed by a wick (generally of cotton) in contact with a resistor. When the user goes to activate his vaping device to aspirate air, the resistor heats up and vaporises the e-liquid contained in the wick. Propylene glycol and vegetable glycerin have low vaporisation temperatures, which makes them suitable supports for the conveyance of the flavouring and nicotine.
Contrary to cigarette smoke, which can remain in suspension in the air for several minutes or even hours, the vapour of an e-cig is only visible for 15 to 20 seconds. The millions of droplets which make up the vapour evaporate very quickly on contact with air.