So I'm down in the basement workshop cleaning off a piece of steel I salvaged from the case of an old window airconditioner for a project I'm working on. I'm using a bunch of different tools; drill, pad sander, torch, angle grinder, power shears...
At one point after sending loads of sparks into the air with the grinder, I go to set it down on the work bench and glance down to see "fog" escaping from the valve of the propane torch. It is a torck head like this;
With a separate valve on the burner, so I normally just leave the tank valve open while it I'm working.
I quickly grabbed the torch and rushed outside to take the valve off. 
Now I'm upstairs for a bit to leave the shop air out before I start throwing more sparks.
Be safe out there...
