It wasn't an O2 tank, it was a 140 cuft acetylene cylinder.I've drove those for years. When a tank wants to go it lets you know. I usually pull off though and find a parking lot. Roll it off and open it up.Reminds me of those Jumpin' Jack fire crackers I had as a kid...or cherry blossoms.Most likely an acetylene cylinder. Oxygen does not burn, only rapidly accelerates other item burning.