Purpose Electronic nicotine delivery systems (ENDS) purport to deliver nicotine to the lungs of smokers. Five brands of ENDS were evaluated for design features, accuracy and clarity of labelling and quality of instruction manuals and associated print material supplied with products or on manufacturers' websites.

Methods ENDS were purchased from online vendors and analysed for various parameters.

Results While the basic design of ENDS was similar across brands, specific design features varied significantly. Fluid contained in cartridge reservoirs readily leaked out of most brands, and it was difficult to assemble or disassemble ENDS without touching nicotine-containing fluid. Two brands had designs that helped lessen this problem. Labelling of cartridges was very poor; labelling of some cartridge wrappers was better than labelling of cartridges. In general, packs of replacement cartridges were better labelled than the wrappers or cartridges, but most packs lacked cartridge content and warning information, and sometimes packs had confusing information. Used cartridges contained fluid, and disposal of nicotine-containing cartridges was not adequately addressed on websites or in manuals. Orders were sometimes filled incorrectly, and safety features did not always function properly. Print and internet material often contained information or made claims for which there is currently no scientific support.

Conclusions Design flaws, lack of adequate labelling and concerns about quality control and health issues indicate that regulators should consider removing ENDS from the market until their safety can be adequately evaluated.