Figure 2. Examples of different electronic cigarette (e-cigarette) products.
Many ENDS products are designed to look like traditional tobacco cigarettes in an effort to replicate the visual, sensory, behavioral and social aspects of smoking. Additionally, many other electronic devices that deliver nicotine and/or other substances have been developed including disposable e-cigarettes, rechargeable e-cigarettes, pen-style medium-sized rechargeable e-cigarettes (sometimes called “vape pens”), tank-style large-sized rechargeable e-cigarettes, e-cigars, e-pipes, and e-hookah.43 The e-cigarette is composed of three main components: a rechargeable lithium battery, vaporizing chamber and a cartridge that contains the liquid nicotine.7
The lithium battery is the most critical part of the e-cigarette and responsible for activating the device to charge the atomizer inside the cartridge. The vaporizing chamber, also known as the atomizer, is responsible for vaporizing the nicotine liquid within the cartridge. Attached to one end of the battery is a LED indicator light; the indicator light becomes active when the user inhales. The e-cigarette then triggers the display of the red light; once the smoker stops inhaling or if the battery charge is low, the indicator light will switch off.8
To activate an e-cigarette, the user will either press an activation button or merely inhale against the device causing an air flow to signal the inbuilt sensor within the lithium battery to activate the vaporizing chamber. The vaporizing chamber converts the liquid nicotine in the cartridge into a vapor, which is then inhaled by the user. Upon exhalation and coming into contact with the moisture in the outside air, the vapor condenses resulting in a thick visible fog.
The e-cigarette industry continues to evolve, new products are quickly developed and brought to the market. Since 2003, when the first generation e-cig was first introduced by Hon Lik three generations have followed. First generation e-cigarettes resemble traditional cigarettes, they are cheap easily accessible and often times disposable. The second generation or “mid-size” e-cigs tends to be more favored towards experienced e-cig users. They are considerable larger, rechargeable and consist of two parts, a separate tank and a battery.77
Unlike the first generation e-cigs, the second generations contain a clearomizer and not an atomizer. The clearomizer was developed in 2009, it was the first technology that contained the wiking material, reservoir and the atomizer coil all within one single unit.79
Third generation e-cigarettes are essential a larger type of the second generation e-cigs.66 They are often referred as modifications e-cigs or “mods” the device comes in a variety of shapes and sizes, typical a box or cylindrical shape, where the user can customize tank, how much e-liquid is contained and the voltage or power the device can output.79
The fourth and most recent generation that is developed, are considered the most powerful and advanced device on the market.68 Typically made up of stainless steel cylindrical box. The device has a temperature regulating system and lower resistance coils (Sub Ohm) to produce bigger more flavorful vapors.79
There are two major types of nicotine cartridges available for use in an e-cigarette. Most basic cartridges are disposable cartomizers. These cartridges are prefilled with e-liquid. Once the cartridge is used up, it is thrown away and requires replacement with a new cartridge. The other type of cartridge contains a refillable reservoir where the e-liquid drips into a refillable cartomizer and is reusable.9
Additional components of the e-cigarette include the USB, vehicle, portable wall and personal chargers. These components are required as the power source for the e-cigarette.10
Figure 3. A bottle is filled with nicotine "juice" solution at an e-cigarette factory in China.