"LDosser" wrote in message
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"litteratuer" takenonotice@all wrote in message
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"Leon" wrote in message
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Vapor literally does not exist with out air, vapor is simply difused
matter suspended in air.

It might seem so, but that is not the case.

Gasoline vapor is heavier than air. With air given a vapor density of 1,
the vapor density of gasoline is between 3 and 4.

In an undisturbed tank, vented to the outside, as gasoline evaporates,
the vapor will displace the air.
In the case where all of the gasoline has been drained and air has
entered the tank, the remaining vapor will be concentrated at the bottom.



And some fool will try to weld the 'empty' tank ....


Sadly, it does happen.

Many years ago a young neighbor of mine was using an oxy-acetylene torch to
cut open a fuel tank which he had emptied some time beforehand and thought
was safe. It exploded, leaving him with serious permanent brain damage.