The devices' lithium-ion batteries exploded in 15 incidents between October 2015 and June 2016 that were reported in a Navy memorandum; In two of those, the power sources detonated while the e-cigarettes were in sailors' mouths. Some occurred on vessels, two required shipboard firefighting equipment to extinguish and one forced a naval aircraft to abandon its flight and return for landing after the device in question started filling the cabin with smoke.
Sailors ashore will still be able to use their e-cigarettes while on the Navy's land-based facilities within designated smoking areas. But while shipped out, everyone aboard -- including civilians or visitors -- must abide by the ban. The prohibition goes into effect 30 days after the new policy is released on May 14th, so vape 'em if you got 'em.