Four generations of e-cigarettes

1st generation2nd generation3rd generation4th generationRemarks
Open/closed systemClosedOpenOpenOpenAn open system is manufactured with a clearomiser which is manually filled with e-liquid
A closed system is prefilled with e-liquid which is directly attached to the battery
DesignCig-a-likePens/laser pointerTank-style devices, also called “mods”Tank-style with better regulatory features: “regulated mods”The design of e-cigarettes has become more complex over time
Currently available devices are larger and come with temperature controls
Cartridge refillNo RefillRefillableRefillableRefillable
Voltage∼3.7–4.2 V∼3.7–6 V∼6–8 V∼3–8 V with variable wattage (1–75 W)High voltage results in heating, which causes release of toxic compounds that have health implications
Battery type and capacityBrushed steel batteryeGO-style battery; lithium-ion batteryICR lithium-ion or IMR lithium-ion batteryLithium-polymer battery (Li-Po)Most of these battery packs can short-circuit and may cause explosions
BrandsVAPESTICK, Vype Disposable, Aer Disposable and NJOYBlu+, Eonsmoke, VaporFi Rocket, Apollo vTube 4.0 and VaporFi Pro IIVaporFi, Halo, Mig Vapor and KangerTechV2, JUUL Vapor, South Beach Smoke, Diamond Series, Vapor Shark

ICR: LiCoO2 cathode; IMR: LiMn2O4 cathode.