Hydrogen fuel cells may revolutionize the transportation sector, and possibly, home electricity as well. It’s the fuel—the liquid hydrogen—that undergoes the reaction inside the fuel cell that gives most skeptics pause. It’s kept under intense pressures of 3,000 to 10,000 lbs. per square inch, it’s flammable and the thought of it recalls images of the Hindenburg disaster. The fear is partially built on myth, but there are safety concerns to consider before switching to a hydrogen economy.
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Hydrogen is explosive at high concentrations, but its tendency is to burn rather than to explode. That property doesn’t eliminate the explosive danger entirely, but it renders it as safe as any volatile material that is used as fuel. Hydrogen tanks have been subjected to rigorous testing and worst-case scenarios. In a study published in the November 1996 issue of "The New Scientist," physicist Rob Edwards tested a full hydrogen tank by engulfing it in a 1600-degree flame for 70 minutes without incident. He also punctured a tank with armor piercing bullets. The hydrogen sometimes burned and sometimes dissipated, but it did not explode.
Hydrogen is extremely flammable, as any chemistry student who has ignited hydrogen in a test tube can attest. It takes 14 times less energy to ignite hydrogen than it does to ignite natural gas, according to a white paper by Amory Lovins for the Rocky Mountain Institute. It does require a concentrations in the air four times higher than gasoline vapor for ignition, however, making hydrogen as fuel a danger similar to any flammable fuel in use today, according to Lovins. Hydrogen does pose an added danger to first responders in the event of a fire because a hydrogen flame is virtually invisible in daylight.
Liquid hydrogen immediately effervesces on contact with air at standard temperature and pressure. An abundance of gathered hydrogen in areas that are not well ventilated poses an asphyxiation risk to people in the area. Hydrogen gas is odorless and colorless, and the reaction with oxygen that would turn the free hydrogen into harmless water vapor happens very slowly at ambient temperature. As a result, the free hydrogen creates an oxygen-deficient environment that can cause headaches, depression of the senses, unconsciousness or even death.
Hydrogen can be extracted from a number of “feedstocks,” including natural gas, water and even oil and coal. The majority of hydrogen for industrial uses is extracted from fossil fuels in a process that releases abundant amounts of carbon dioxide into the atmosphere, according to the Natural Resources Defense Council. Even hydrogen extracted from water, on the whole, does so with electricity produced by fossil fuel sources. Until hydrogen production is carbon neutral, powering cars with hydrogen will not be an effective global warming mitigation strategy.