"Modat22" wrote in message
...
I need to make sure it won't explode and was thinking about letting it
sit in the sun open for a few days then fill it completely with water.

Any other ideas?

The way that fuel tankers are degassed is to wash the interiors
with hot (+70C) soapy water, then rinse out all suds etc.
Put a steam hose inside each compartment and steam the interiors
for at least 30 minutes. Let the tanker cool, then get a hydrocarbon
gas detector and check for any vapours. The testing has to show
less than 10% of the lower explosive limit for the last product
carried - eg petrol 1.3% LEL has to show 0.13% or less on the
gas detector. If you get that result then work can start straight
away. If the tanker is not worked on for 2 or more hours it has
to be retested before work can start.

Most metals and alloys will absorb petroleum products, and with
heating will release vapours which can ignite and under the right
air/vapour mix will explode. The addition of various anti knock
compounds to unleaded fuel makes it even harder to degas a tank
as they form a gum like layer if just steamed - hence the hot water
wash.

I know the above seems a lot to do for a small fuel tank, but every
so often I see reports of some poor sod who has lost his life by
welding/grinding/drilling into a fuel tank or more often a 205 litre
drum. The combustible liquids - oils, diesel, grease, detergents even
seem to present a greater danger as people do not recognise those
products as being dangerous when heated above their ignition
temperatures. Most people tend to take care with petrol and at least
do a basic degas.