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How Safe is Hydrogen?


The Hindenburg Disaster - Is Hydrogen Really Dangerous?

The May 1937 explosion of the German airship Hindenburg has dogged the development of hydrogen as a fuel since those first terrifying images played out across newspapers and newsreels throughout the world. For years, the hydrogen gas that filled the airship and allowed it to float in the atmosphere was blamed for the raging inferno that consumed the craft in just seconds. Turns out that’s not the case at all.

So What Really Happened With the Hindenburg?

Theories abound—everything from sabotage by operatives to a fuel leak and overheating engines—as to the cause of the initial fire. While speculation about conspiracies will always exist on the periphery, the hydrogen gas that provided lift to the craft was not the main contributor to the fire. Thorough investigation has boiled it down to a fairly well agreed-upon scenario.

The surface skin of the airship was covered with a layer of iron oxide and a coating of reflective aluminum paint. These two chemical compounds are highly flammable and burn at a very aggressive rate. The skin most likely ignited from an atmospheric discharge (a spark) or perhaps a lightning strike as the airship was docking during the waning phases of an electrical storm. Reasonable corroboration of this theory was demonstrated in an experiment by retired NASA engineer Addison Bain in which remnants of the actual surface skin of the ship were set ablaze some 60 years after the accident—and they still burned as ferociously as they did that fateful day.

While the hydrogen gasbags in the ship did eventually succumb to the heat and rupture, the escaping gas caught fire as the surrounding skin burned. But being lighter than the air around it, the burning gas rose quickly and burned well above the passenger compartment and crew quarters below, and completely burned itself out within 60 seconds.

As the craft and the hydrogen inside it was consumed by the initial inferno and the skeletal frame of the ship plummeted, the on-board stores of diesel fuel (which powered the maneuvering engines) caught fire and those continued to burn as the wreckage lay on the ground. Had the Hindenburg been filled with non-flammable helium instead of hydrogen, the same basic sequence would still quite likely have ensued. The skin still would have ignited, the lifting gas would have escaped and the crippled dirigible would have plunged to the ground with the onboard diesel fuel aflame.

The tragedy of this accident is multifaceted. Not only was there terrible loss of life, but also the burgeoning and successful airship industry was dismantled and a stigma was attached to hydrogen—a frankly unjust stigma that lasts to this day.

The Basic Nature and Characteristics of Hydrogen

  • Hydrogen is non-toxic.
    It is a naturally occurring, basically benign element found freely in the atmosphere. By comparison, petroleum fuels are extremely toxic.

  • Hydrogen is less flammable than gasoline.
    The auto-ignition temperature of hydrogen is 932 degrees Fahrenheit. Compare that to gasoline’s auto-ignition temperature of 536 degrees Fahrenheit (auto-ignition temperature is the minimum temperature at which a fuel will ignite without a spark or flame). Yes, it’s actually easier for gasoline to spontaneously combust.

  • Hydrogen disperses quickly in the atmosphere.
    Because hydrogen is so light (about 15 time lighter than air) it easily dissipates and if a leak or spill does occur, the hydrogen becomes rapidly sparse and difficult to ignite. And even if it does catch fire, it burns itself out very quickly. By contrast, heavier fuels such as diesel oil and gasoline do not rapidly dissipate and remain a fire threat for a longer period of time.

  • Hydrogen stores safely.
    The tanks used to store hydrogen, whether in its gaseous or liquid form, undergo demanding testing procedures. They must endure extreme heat and external pressure forces as well as collision impacts. Conventional gasoline and diesel fuel tanks are, in most instances, simple stamped steel shells that do not undergo these stringent stress tests.

  • Hydrogen is clean.
    The single emission from burned hydrogen is water vapor—that’s it. Compare that to particulate matter (soot), NOx, CO, CO2 and—among other toxic emissions—from burned petroleum fuels.

It Really Boils Down to Common Sense

Think about it. The world that we’ve created for ourselves—with all of our technological developments—is fraught with hazards. But it’s also filled with potential—a cornucopia of good ideas that can make our lives better, easier and richer. The caveat here is that it isn’t just automatic, it requires attention and intelligent use.

We have all learned to handle dangerous but useful tools in our daily lives. We don’t think twice about slicing a loaf of bread with a sharp knife, striking a hot match to light a candle or driving down the road in a car filled with a tank of explosive gasoline. We don’t think about their dangers because we’ve learned to be smart and judicious in their use.

It is much the same case with hydrogen—new to us as a motor fuel, proper handling and safety techniques will require a learning curve. Engineers have done their part and developed safe and effective processes for transporting, storing and dispensing the fuel. It’s up to us as users to be cognizant of the rules and to follow them.

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