Figure 2 is schematic of typical e-cigarette components. E-cigarettes contain a liquid, typically
propylene glycol and/or glycerol, that contains varying amounts of nicotine (e.g., 0-36 mg/ml as
found in on-line advertisements for e-cigarette fluids) as well as flavorants. A wicking material
is used to transport the liquid by capillary action from a reservoir to the heater. When the user
draws on the e-cigarette, a sensor detects the draw and a micro-processor activates the heater
which vaporizes the fluid to produce a saturated vapor at a temperature greater than 350 oC, [1,
Schripp]. Some e-cigarettes, such as those with refillable tanks, have heaters that are manually
controlled with a button. Propylene glycol, glycerol, and nicotine are each liquids with relatively
high boiling points; propylene glycol (188 oC), glycerol (290 oC), and nicotine (247 oC).
Consequently the vaporized fluid immediately condenses upon leaving the heating element1.
forming an aerosol of sub-micron spherical liquid droplets with the visible appearance of smoke
or fog.