The US Navy has moved to ban vaping and possession of electronic nicotine delivery systems (ENDS) aboard its ships, subs, and aircraft. According to the Associated Press, the move follows a recent 8-month stretch in which 12 separate incidents of exploding ENDS put sailors out of commision for a combined 77 days. The ban is temporary but indefinite.
The concern, according to a US Navy news release, are the lithium-ion batteries that power most e-cigarettes. Lithium-ion batteries in any context are at risk of explosion via an overheating feedback process known as thermal runaway. A good lithium-ion battery will have checks in place to make doubly sure that this can't happen, but the e-cig industry is a total Wild West.
According to a 2014 US Fire Administration report, most cases of exploding e-cigs occur as their batteries charge via USB port, a feature of many e-cigarettes. The presence of a USB port means that the devices can be hooked up to any number of different power sources that may or may not align with the battery's specs.
"Few, if any, consumers understand that not all USB ports are 'created equal.' The voltage and current provided by USB ports can vary significantly," the USFA report explains. "Without consulting the technical specifications for the USB power source, it is difficult or impossible for a consumer to determine the power supplied by any particular USB port and even more difficult to determine whether it is safe to use with a particular e-cigarette."
Given its shape and dimensions, an overheating e-cig then has the potential to become a "flaming rocket," which is probably not a good thing to have aboard a battleship or submarine. In any case, sailors that are currently deployed can request extensions on device removal until their next port visit.