RE: Gasoline Ignition
What hasn't been mentioned in this entire thread is that gasoline or
gasoline vapors will only ignite at a critical mix or saturation with air.
But, and a big BUT, when there is a plume of gasoline vapor coming from a
leak or exposure to air somewhere in that plume will be the perfect
mixture.  To close to the source, like at the surface of the gasoline in an
open can or bucket, the density is to high (not enough oxygen) for ignition
and far enough away (not enough gasoline vapor) then no ignition.  But there
is a point in between where the mixture will be perfect.  Anything creating
a spark at that point or an open flame or even a surface hot enough and you
have ignition.  Bottom line is that if you have gas fumes floating around
there is a very good chance the right conditions will cause ignition.