When people hear that hydrogen can be used as an energy source, some are concerned about its overall safety. Hydrogen itself is not poisonous to humans. When hydrogen is burned, the byproduct is steam and a small amount of nitrogen oxide, which are both harmless. To-date, the main concern regarding hydrogen is related to the widespread misunderstanding that it can easily cause explosions.
Hydrogen combusts when its percentage by volume in the surrounding air is between 4 – 75%. Under these conditions, energy equivalent to static electricity is needed to ignite hydrogen. Note that hydrogen can only explode when both of these conditions are met. Further, since the hydrogen atom is the lightest material on earth, and easily diffuses into the atmosphere, it is almost impossible to reach an atmospheric concentration of hydrogen is 4% or more.
Lighter than gasoline and air, and diffuses quickly
When gasoline that has leaked from a corroded tank of a gasoline-powered car is ignited, it will continuously burn due to the fact that gasoline is heavier than the surrounding air. The fire will burn straight through the tires and body of the vehicle. However, in a hydrogen vehicle, because hydrogen is much lighter than air, it quickly combines with oxygen, so as soon as there is a minor combustion, the hydrogen quickly diffuses into the atmosphere. This has a clear advantage when it comes to safety, which has been proved experimentally.
About the Explosion at the Fukushima Daiichi Nuclear Power Station
After the Fukushima Daiichi nuclear disaster occurred in March 2011, many people thought the reactor building was damaged by a hydrogen explosion. While this is correct, the explosion was in fact planned into the reactor’s design to mitigate risk. The release of a buildup of steam and hydrogen, both normal outputs from boiling light water reactors, prevented the reactor vessel from being destroyed, which would have resulted in an even larger amount of poisonous radioactive material being released into the atmosphere.
Facilities that use hydrogen, like Fukushima Daiichi, can avoid catastrophic explosions by releasing hydrogen buildups through ventilation holes. This prevents the two conditions necessary for an explosion to occur: an ignition source and a 4–75% buildup of hydrogen gas in a closed space.
Our modern lives benefit from natural gas lines and propane hookups. While this energy provision is not absolutely safe, it has become widespread because its merits outweigh the risks. Similarly, as hydrogen energy becomes more widespread, certification systems and regulatory frameworks will control various aspects of its provision, and education for engineers who handle hydrogen will be mandatory. Gradually people will become more accustomed to handling hydrogen, and it will become part of our daily lives.