Hydrogen System Safety

Low temperature combustion of hydrogen produces no harmful products. This characteristic leads to several advantages in home use. First and most important, is the lack of potential for the production of highly toxic carbon monoxide. Hydrogen fuel contains no carbon compounds. This fact makes it impossible for the hydrogen combustion process to produce carbon monoxide. This is true no matter what type of burner is used or how maladjusted it is. Irrespective of the health threat presented by air pollution, a number of lives are lost each year due to the leakage of carbon monoxide from improperly adjusted fossil fuel combustion processes. With the adoption of hydrogen these deaths will no longer occur. Hydrogen, like natural gas, can leak and cause an explosive hazard, but there is no danger from poison gas.

The safety precautions for use of hydrogen in the home and in industrial applications are similar to those required for natural gas. Leakage of either gas can result in the build-up of mixtures that can burn or, in some cases, explode. Hydrogen is somewhat harder to ignite with heat than is natural gas, but is more easily ignited with electric sparks. Hydrogen is lighter than air and has a much higher diffusion velocity than natural gas. The low weight causes hydrogen clouds to be buoyant and rapidly float up in the air, much like a helium filled balloon. The high diffusion velocity causes hydrogen to rapidly mix with the air. Because of its buoyancy and mixing properties it is difficult to build up a high concentration of hydrogen near a leak. Unfortunately, this safety advantage is partly offset by the wide combustion mixture range of hydrogen (4 to 75 volume percent) when compared to natural gas (5 to 15 volume percent).

Neither pure methane nor hydrogen has an odor. To increase safety, a trace of a substance with a powerful distinctive odor is added to natural gas. This provides a characteristic odor, allowing people to detect leakage by smell. This same precaution can be applied with hydrogen. The shortcoming of the current method is the odorous substance most used contains sulfur compounds. These burn to sulfur dioxide and contribute to air pollution.

Special analytical equipment is required to detect pure methane or hydrogen. Hydrogen is probably easier to detect because of its low molecular weight and reactivity with many catalysts. At this time, there is no reliable low cost detector, similar to a smoke detector, available for home or industrial use capable of detecting either gas. Natural gas has been used for years with odor as the only simple detection method. Inspired by the switch to hydrogen researchers may develop a simple detector for continuous monitoring of hydrogen in the air. A hydrogen detector is under investigation at the University Of California, Irvine California. 199 It has the potential of being small and inexpensive. If successfully developed, this detector will result in an energy distribution system using hydrogen that is safer than the current natural gas system.

As previously mentioned, much data on hydrogen use and safety is available from: The International Association for Hydrogen Energy (IAHE), P. O. Box 248266, Coral Gables, Florida 33124

Their resources include: The International Journal of Hydrogen Energy (13 volumes), The Proceedings of the World Hydrogen Energy Conference (7 Conferences) and related material.

199 Favier, Frederic, Walter, Erich, C., Zach, Michael P., Benter, Thorsten, Penner, Reginald M., "Hydrogen Sensors and Switches form Electrodeposited Palladium Mesowire Arrays", Science. Vol. 293, No 5538, Page 2227

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