- Cartridge: The cartridge serves as a liquid reservoir and mouthpiece. It is designed to allow the passage of liquid into the atomizer, and vapour from the atomizer to the user's mouth. Most models utilize a sponge to keep the liquid in place, while some employ a tank that holds loose fluid. When the liquid is depleted, users can refill the cartridge or replace it with another ready-filled cartridge.
- Atomizer: The atomizer is the central component. It generally consists of a small heating coil and wicking material that draws liquid in.
- Cartomizer: Since atomizers tends to lose efficiency over time due to a buildup of sediment, or "burn out" entirely, some models employ a cheaper disposable "cartomizer" component that also doubles as the device's cartridge. The piece consists of a heating element surrounded by a liquid-soaked poly-foam.
- Power: Most portable devices contain a rechargeable battery, which tends to be the largest component of an electronic cigarette. The battery may contain an electronic airflow sensor whereby activation is triggered simply by drawing breath through the device, while other models employ a power button that must be held during operation. An LED to indicate activation may also be employed. Some manufacturers also offer a cigarette pack-shaped portable charging case (PCC), which contains a larger battery capable of charging e-cigarettes. Devices aimed at enthusiasts may sport additional features, such as variable power output and support of a wide range of internal batteries and atomizers.
Liquid for producing vapor in electronic cigarettes, commonly known as e-juice or e-liquid, is a solution of propylene glycol(PG), vegetable glycerin (VG), and/orpolyethylene glycol 400 (PEG400) mixed with concentrated flavors; and optionally, a variable concentration of nicotine.
The solution is often sold in a bottle or in pre-filled disposable cartridges. They are manufactured with various tobacco, fruit, and other flavors, as well as variable nicotine concentrations. The standard notation "mg/ml" is often used in labeling for denoting nicotine concentration, and is sometimes shortened to a simple "mg" Nicotine-free solutions are also common.