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Science Forum Index » Energy - Hydrogen Forum » How dangerous is hydrogen really when compared to gasoline?
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 Posted: Wed May 30, 2007 12:05 am |
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I was called a liar recently because I made a statement I thought was
uncontroversial. Namely, that hydrogen does not spontaneously
explode! haha..
Obviously that person was someone who didn't know what he was talking
about.
Here are the facts;
Hydrogen is a fuel. And as a fuel it can explode certainly. But it
doesn't do so spontaneously. It does so only when three conditions
are met;
(1) There has to be an oxidizer present
(2) Oxidizer and fuel have to be in the right ratio - the explosion
limit
(3) There has to be a spark to set it off.
If all three conditions are not met - then an explosion CANNOT take
place.
Now, there are things that explode spontaneously. Things like
hydrogen peroxide. Pour a 3% solution of it on a wound and it will
bubble madly. A 97% solution will explode! Nitroglycerin is another
substance that can explode spontaneously. Hit it with a hammer and it
will explode.
Hydrogen does not explode spontaneously. It cannot.
If hydrogen is kept away from oxygen and air, it cannot burn or
explode.
If hydrogen leaks out of a container air is present, but that
container can be equipped with a sealant and a MEMS based sensor that
releases the sealant if an unscheduled pressure drop occurs - and then
that tank's filling apparatus is disabled and the tank calls for
service and must be replaced.
If an uncontrolled leak occurs then air is present and explosive
limits can be reached. But, since hydrogen disappates so quickly
compared to methane or gasoline vapors, there is little time for a
spark to set it off.
And if there is a spark and the mixture is set off, the blast is far
less dangerous than methane or gasoline vapor due to the speed at
which hydrogen disappates again.
Now, how safe is gasoline anyway? Well according to the fire safety
folks there are over 10,000 incidents a month where automobiles catch
on fire due to faulty fuel lines and fuel systems. Most of the time
people aren't in those cars, but still, 5,000 people a year lose their
lives to gasoline fires. Another 1,000 fires per month occur at gas
stations. These are uniformly under-reported. I'm certain that the
first hydrogen explosion won't be similarly reported.
Are liquids inherently safe and gases inherently unsafe? No its just
the opposite. Gases fill the containers they occupy, and there is no
chance for oxidizer to get into them. So, the first condition for a
fire is never met. Not so for liquid filled containers that are
partly filled with fuel and partly filled with air - containing
oxidizers.
Is filling gaseous tanks dangerous? You tell me. Ever have a propane
bottle refilled? How hard is that? A very simple system of valves
keeps everything safe. Something that can easily be put in your car's
hydrogen gas tank.
No, safety is not the bugaboo some in the oil industry would have us
believe. In fact, while major oil companies have written scientific
papers on the dangers of hydrogen through their alternative energy
divisions, these same companies have gone out of their way to supress
reporting and safety concerns of the more than 130,000 injuries per
year caused by gasoline explosions that produce over half a billion
dollars in property damage each year and cause 5,000 deaths - nearly
10% of ALL deaths on the highway!!!
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