Another problem with Halons is they have no cooling properties. The
statement that "Once the fire is out, it is out" is not strictly correct. If
the engine is still hot enough it will reignite as soon as you remove the
halon. The triangle of combustion states you need 3 things for combustion to
occur:

1. Fuel
2. Heat
3. Oxygen

So you can put a fire out by removing any side of the triangle. Halons
remove the oxygen but as soon as you remove the halon, the oxygen is back.

Water removes the heat so even when you remove the water there isn't usually
sufficient heat to re-ignite.

The third side of the triangle can be removed by either removing the
fuel(Gasoline, an old rag you forget, etc.) or just letting the van burn
until there is no more fuel left, the contents of the van also count as fuel
in this equation.

Although no one wants to see their beloved van burn just remember, you can
get a new van, human bodies aren't that easy to replace. Saying that though,
every TV show I have ever seen where the vehicle was in an accident or fire,
it has blown up. I was a firefighter in England for 11 years and we had a
particularly busy freeway close by. I have attended over 100 car smashes and
never seen one explode. I have also seen hundreds of car fires, sometimes
where there was not much more than shell left when we got there and none of
them ever exploded either.

You would have to make a judgment call as to how much you are going to do
with a burning vehicle before you give up but you should always err on the
side of safety without getting too Hollywood explosion paranoid.

Melvin

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