I wonder who was in charge of the safety committee that day?? Possibly with the initials of ..... J.M? And he can't even say he wasn't there to witness it, he was taking the picture
Man, I see you can't expect a break from this crowd! My guess is the tank was full of water or more likely inert gas (not gasoline for sure). But then I'm just guessing
Added in edit:
Not that most would go to the trouble, but if you did want to test a pressure vessel (air tank) the safe thing to do is fill it with water and take the pressure up to 1 1/2 times the operating pressure, let it set for hour or so. Fact is I'm not really comfortable mentioning exact "how to info" since a very detailed set of steps are required as detailed in ASME specs that Mr. Google can provide. Suffice to say, if one runs enough temporary black pipe so the vessel/tank can be pressured up from a safe distance and location (this includes the montoring pressure gauge) then it's a much safer thing than just letting the air compressor do it's job while you stand there and watch. Hydrostatic (pressurized water) testing is a MUCH safer way to test when compared to pneumatic (nitrogen or air).
