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OK,
fireman's perspective: The issue with propane is that it is a
liquefied gas. What that means (I know most of you know this) is
this:
1: At normal ambient temperatures, and at
atmospheric pressure (open air) it will always be a gas.
2: To be stored efficiently, it has to be
compressed. When it gets compressed, it's boiling point increases and it
stops boiling and becomes a liquid.
3: First problem (though a small one), as is it
released, it absorbs an enormous amount of energy as it changes from a liquid to
a gas. The process of boiling absorbs a lot of heat, even when the boiling
point occurs well below zero (the fittings get cold because they are drawing all
the surrounding heat away, into the liquid/gas transfer). Thus, there is a
thermal issue for fireman when there is a propane leak. Remote as it may
seem (and is) a person can be injured by the cold issue during a major
leak.
4: Propane also expands (I think it is 800 times,
but I do not have any books at home), so, as 1 cubic foot of liquid converts to
gas, it produces 800 cubic feet of gas. Or, one of our tanks on our
trailer really represents 800 tanks of gas. A BUNCH.
5: That gas not only fills the area, but it does
it 3 dimensionally, up, down and across, potentially filling (for example) a
tunnel. Simply, a leaking flammable gas in an enclosed area is VERY
dangerous.
6: The expanding gas cloud can and will dissipate
oxygen. A person can easily suffocate, not because it is propane, but
because the propane has pushed the oxygen out of its
way.
7: The gas is nearly impossible to
"control" It is going to move where it wants to.
7: Inside the tank, propane can become very
dangerous. If the liquid is heated by an outside source, it will start to
boil. As it boils, the pressure increases, as the pressure increases, the
boiling point increases and it stops boiling, as it gets heated it boils,
increases pressure, blah,blah,blah. As this occurs the tanks needs to vent
itself, which it will do (that's why you smell it on a hot summer day).
When the heating and boiling overpowers the venting system, something wants to
give. Typically it is a pretty exciting time period. I had two 100
Lbs. cylinders blowup in the back of a truck on fire just last month, really
cool to watch, but then again, not so cool.
OK,
now compare that to gasoline. Gasoline is actually a pretty tame puppy in
the fire services eyes. You can see it, you can tell where it is going,
you can cover it with foam, you can absorb it with sand (or other materials), it
basically does not displace oxygen (at least not to the extent that propane
would), it is limited to the amount in the vehicle tank (it is not a growing
animal as it leaks basically), and it is reasonably easy to stop from
flowing. Also gasoline tanks do not explode like in the movies, yes it can
rupture, and yes you could, under very remote situations have an explosion, but
basically, the tank burning is no big deal.
Now
having said all that, propane is not really that bad either. It is one of
the safety industries, with well designed safety systems.
Different areas have different rules on how you handle
your propane tanks, but this might help as to why they have the
rules.
Also,
one other note, propane powered vehicles typically have specially designed
tanks.
Now,
how about this one, compressed or liquefied natural gas, even a bader player
that is becoming more common
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