Good trick I used to do was on sealed copper pipe where its being nitrogen purged is fill the end with oxy/acety and then go back to where the brazing is being done , crank up the nitrogen and get the apprentice to stand at the end of the pipe and start brazing.
KABOOOOOOM
OOh and yes we set fire to an acetylene bottle once. Not something I would want to repeat.
you rotter norcon
had that done to me once needed a clean pair of duds