“Hydrogen is explosive, but supply is a bigger issue for the nascent industry. For all the volatility of a gas like hydrogen, which combusts with one-tenth the energy required for gasoline, hydrogen fuel cell vehicles are safer than cars with internal combustion engines, according to industry experts.” [1]
[1] Lucas Mearian for Computerworld: http://www.computerworld.com/article/2852323/heres-why-hydrogen-fueled-cars-arent-little-hindenburgs.html