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At the 2001 National Hydrogen Association conference, Dr. Michael R. Swain presented the results of a study which compared ignited fuel leaks in hydrogen and gasoline powered vehicles.

As you can see the damage to the gasoline vehicle was severe while the hydrogen vehicle was minimal. In fact, the maximum temperature measured on the rear window of the hydrogen vehicle was 117˚F.

Burning hydrogen produces significantly less radiant heat that burning gasoline or natural gas. Therefore, the risk of secondary fires igniting is low but objects that come in contact with a hydrogen flame burn immediately.

The stoichiometric mixture, where it is the mixture where a gas is most easily ignited in air, is 29% for hydrogen and 2% for gasoline.

The simulation shows just how rapidly hydrogen released into the atmosphere dissipates. Therefore, vehicle engineers need to take this property of hydrogen into account when placing the fuel tank in a vehicle so possible leaks do not accumulate hydrogen in an area where the gas may be trapped.