"Mr. cod"'s arguments, while in themselves factually correct, actually are strawmen. The hydrogen economy is NOT talking about liquid hydrogen. Transmission and storage will be as compressed gases, not liquid. Sure, hydrogen-air mixtures become flammable at 4%--but we already know how to work with hydrogen--thousands of laboratories do it every day (running gas chromatographs with flame ionization detectors)--working with hydrogen is actually LESS dangerous than filling your automobile up with gasoline. The "invisible flame" problem is fixed in a manner analogous the the current use of natural gas (natural gas is odorless--so we ADD a chemical which has an odor--for hydrogen we ADD a trace chemical which emits light in the visible spectrum if there is a flame--a few ppm of benzene vapor will probably do the trick). Using hydrogen safely is NOT rocket science--despite Snope's assertions to the contrary.