The American Boat & Yacht Council that develops voluntary standards
and practices for the marine industry first approved the use of
"cooking appliances with self-contained cylinders" in 1993.
Key parts of the standard include:
storing all spare cylinders in a protected, self draining location on
the exterior of the boat, where vapors can only flow overboard;
and storing appliances with attached cylinders (limited to eight ounce
capacity) in a ventilated location in the boat interior.
I believe the thinking is that the typical cylinder stored in the
boat will be half full and that it is difficult to maintain an
explosive mixture in a ventilated area with only four ounces of fuel.
Perhaps one of the engineers among us can repeat the calculation of
what volume of air would be required to render four or eight ounces of
butane nonexplosive.
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A note from the same thread:
The explosion limits for butane in air at 20 C, atmospheric pressure
are 1.9 (lower explosion limit) and 8.5 (upper explosion limit) in
volume percentage. The relative density of butane is about 2, which
means that one ounce off butane will form a explosive mixture if mixed
with about 26 - 6 ounces off air, or between 0.75 and 0.167 kg.
Density of air (dry) is about 1.3 kg/cub. meter, so if you mix one
ounce of butane with between 0.6 and 0.13 cub. meter or about 21 and
4.6 cubic feet you will get an explosive mixture.
But remember, butane does not mix too well with air, so even if the
mean concentration of butane is outside these explosion limits, the
concentration might well be within the explosion limits in part of the
space.
I once had a small butane explosion/fire outside in the open air on a
grass field when I changed a gas tank on a camping cooker and then lighted
the cooker to test it. The butane that had leaked out during the
replacement of the tank (much less then one ounce) had filled a small
hollow in the ground, and, as there was almost no wind, remained
there. When I then lighted the cooker this leaked gas caught fire.
So, on the above question "would there be an explosive mixture in a 30
footer if a entire tank of the type used to refill lighters were to
leak in the boat", the answer is: yes there will be, somewhere in the
30 feeter, and it is very difficult to guess where.