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Old 12-05-2016, 11:44 AM   #202
glatt
 
Join Date: Jul 2003
Location: Arlington, VA
Posts: 27,717
Hydrogen fuel is safer than gasoline.

In a nutshell, hydrogen is more likely to leak than gasoline because it has to be transported under high pressure and the atoms are very small and easily able to escape through smaller holes.

But unlike gasoline, if it does leak, it doesn't hang around or pool on the ground. It disperses faster than most other gasses. It is the least dense gas and will just float right up to the top layers of the atmosphere.

This is a good report on the topic.

Quote:
In many actual leak situations the key parameter that determines if a leak would ignite is the lower flammability limit, and hydrogen’s lower flammability limit is 4 times higher than that of gasoline, 1.9 times higher than that of propane and slightly lower than that of natural as.
...

The conclusion of this study is that in a collision in open spaces, a safety-engineered hydrogen fuel cell car should have less potential hazard than either natural gas or a gasoline vehicle. In a tunnel collision, a hydrogen fuel cell vehicle should be nearly as safe as a natural gas vehicle, and both should be potentially less hazardous than a gasoline or propane vehicle, based on computer simulations comparing substantial post collision release of gasoline and natural gas in a tunnel. The greatest potential risk to the public appears to be a slow leak in an enclosed home garage, where an accumulation of hydrogen could lead to fire or explosion if no hydrogen detection or risk mitigation devices or measures are applied (such as passive or active ventilation).
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