There are many myths about hydrogen which have recently been dispelled. Two years ago, a study of the Hindenburg incident found that it was not the hydrogen that was the cause of the accident. Safety tests performed by Ford Motor Company for the U.S. Department of Energy have found that the technologies being tested for storing hydrogen in a fuel cell vehicle are actually SAFER than storage of gasoline.
The following quotes are taken from "Direct-Hydrogen-Fueled Proton-Exchange-Membrane Fuel Cell System for Transportation Applications: Hydrogen Vehicle Safety Report" by Ford Motor Company, May 1997: Pg 17-18: "Addison Bain, a retired NASA safety expert, has conducted a comprehensive investigation of the Hindenburg incident, searching through archives in both the U.S. and in Germany, interviewing the few remaining witnesses including surviving crew members, and even securing the services of NASA scientists to analyze fragments of the Hindenburg saved as souvenirs. . . Bain's most startling hypothesis is that hydrogen may not have played a major role in the fire. He cites several witnesses that saw what could have been 'St. Elmos fire," -- lightning bolts attracted to the surface of the giant airship. His thorough analysis of the mechanical structure of the dirigible shows that any hydrogen leaking from the inner bags would have been vented to the outside. He shows from historical records and actual analysis of remaining fragments of the ship's gas bags that the construction was either cellulose acetate or cellulose nitrate. Both are flammable. . . In addition, aluminum flakes were added to the covering material to help reflect sunlight to keep the gas bags cool. But Bain points out that cellulose nitrate and metal chips are also the ingredients of rocket fuel, politely suggesting that it might not be wise to paint airships with rocket fuel! His final slide shows a photograph of another burning airship, engulfed in flames much like the Hindenburg. But with one major difference: this airship was filled with inert helium, not hydrogen, suggesting that the Hindenburg fire could very well have been started by lightning igniting highly flammable fabric on the airship. While hydrogen clearly added to the conflagration, the Hindenburg might have burned even if it had been filled with helium. In retrospect, the Hindenburg was a high riisk venture, since the 190,000 standard cubic meters (6.7 million SCF) of hydrogen was carried in a set of rubberized cloth bags, with little protection from outside disturbances. The energy content of the hydrogen was equivalent to about 1,900 gigajoules (GJ), or 19 GJ per passenger. A modern hydrogen-powered vehicle would be much safer, with energy stored in crash-tested tanks instead of flimsy cloth bags. A fuel cell electric vehicle would carry about 0.8 GJ of hydrogen energy for a four-passenger car, or 0.2 GJ per passenger. The hydrogen would be stored in one or more fiber wrapped composite tanks that could survive 50-mph head-on collisions, engulfment by a diesel fuel fire, and pressures at least 2.25 times design pressure without rupture. The message is clear: a modern fuel cell electric vehicle would have 2300 times less hydrogen energy content than the Hindenburg, or 100 times less per passenger, and the hydrogen container would be immeasurably stronger. In effect, there is no comparison between the safety aspects of the Hindenburg and those of a fuel cell vehicle."
With regards to the probability of a rupture of the hydrogen storage tank, Pg 30: "Each tank is tested at 1.5 times its rated operating pressure, and samples from each lot are pressure tested to failure. Each tank design must be qualified at 2.25 times normal operating pressure. Each class of tank is also subjected to gunfire and must not explode but leak only through the bullet-hole." (Try doing that to a gasoline tank!)
Pg xi: "In a collision in open spaces, a safety-engineered hydrogen FCV shound have less potential hazard than either a natural gas vehicle or a gasoline vehicle due to four factors. First, carbon fiber wrapped composite storage tanks (the leading high pressure storage tank material due to its low weight) are able to withstand greater impacts than the vehicle itself without rupture, thereby minimizing the risks of a large release of hydrogen as a result of a collision. Second, hydrogen, if released, disperses much faster than gasoline due to much greater buoyancy, reducing the risks of a post-collision fire. Third, the FCV will carry 60% less total energy than a gasoline or natural gas vehicle, resulting in less potential hazard should it ignite. Finally, the design recommended here includes an inertially activated switch in each FCV that, in the event of a collision, will simultaneously shut off the flow of hydrogen via a slenoid valve or valves, and will cut electrical power from the battery."
Pg. xii: "Hydrogen has 52 times greater buoyancy and 12.2 times greater diffusion coefficient than gasoline. Thys hydrogen will disperse much more quickly than gasoline or natural gas. Similarly, hydrogen's lower flammability limit is four times greater than that of gasoline."