It did not come from the factory sealed in gas, who can say what
happened, you dont even have a clue. Maybe the flame was blown out
closing the lid because of? wind, poor draw, low flame and the hood
forced it out ? and opening it again gave oxygen to the hot cooking area
with raw gas going boom. Just a guess and possibly operator inexperiance
or many other things, like tank valve freeze , low propane, Propane
hose or connection leak, who knows you have to figure it out or Boom
again, maybe bigger this time. It only a grill not a science project.