Hydrogen safer than gasoline

It is still commonly believed that hydrogen is a highly explosive substance. This prejudice is now proven wrong by a video demonstration with running commentary by Michael Swain, a professor at the University of Miami/USA.

The demonstration is part of the annual hydrogen program review of the US Energy Department. "Fuel Leak Simulation" is one of two presentations by hydrogen safety expert Swain. It shows on a split-screen what might happen in case of a fuel leak in a vehicle (Geo Metro) which is operated on gasoline versus compressed gaseous hydrogen.

During the test the gasoline car leaked five pints of fuel in 3½ minutes, the ignition occurring as soon as a combustible cloud was formed. The hydrogen system released 3,4 pounds of fuel in 100 seconds. This requires the malfunction of three safety means (fail of hydrogen sensor, flow sensing system and flow valve).

The hydrogen flame went straight up in a slender cone shape from the trunk deck and began to peter out after a little more than 1,5 minutes. The burning stopped entirely after about 2 min 20 sec. The gasoline fire, which burned mostly underneath the car, kept going, and when the hydrogen fire went out the gasoline car exploded. It took 30 minutes to extinguish the fire.

Swain explained there was a hydrocarbon gas/air mixture building up inside the car once the fire had started. The lower ignition level limit for hydrogen in air is 4%, which is significantly higher than the 1,5% for hydrocarbon gases in air, which means that gasoline vapor can be ignited easily.

Swain concluded: "No car is perfectly safe, but hydrogen is safer than gasoline."

Source: H2Report, S. Geitmann, Jul. 2001