(189a) The Hazards and Risks of Hydrogen

An analysis was completed of the hazards and risks of hydrogen, compared to the traditional gasoline fuel source. The study was based entirely on the physical properties of these fuels, and not on any process used to extract the energy. The study was motivated by the increased interest in hydrogen as a fuel source for automobiles.

The results show that, for flammability hazards, hydrogen has an increased flammability zone, a lower ignition energy and a higher deflagration index. For gasoline, the auto-ignition temperature is lower and the heat of combustion is higher. Thus, hydrogen has a somewhat higher flammability hazard.

The risk is based on probability and consequence. The probability of a fire or explosion is based on the flammability zone size, the autoignition temperature and the minimum ignition energy. In this case, hydrogen has a larger flammability zone and a lower minimum ignition energy ? thus the probability of a fire or explosion is higher. The consequence of a fire or explosion is based on the heat of combustion, the maximum pressure during combustion, and the deflagration index. Hydrogen has an increased consequence due to the large value of the deflagration index while gasoline has a higher heat of combustion. Thus, hydrogen poses an increase risk, primarily due to the increased probability of ignition.

Of course, a complete hazard and risk analysis must be completed once the actual equipment for hydrogen storage and energy extraction is specified.