As a former firefighter, I can answer this with confidence.
It won't explode.
Worst case scenario is if you put the tank right in front of the forge and it heated up enough to explode, the hose would have been long melted off.
You would have a flame shooting out of the nozzle. In order for something to explode, it has to be pressurized or contained. Unless the tank was instantly superheated, the lack of pressure (because of the open valve) would prevent an explosion.
I have personally put out large propane tanks that were on fire. The only way to do it is to reach in and turn off the valve while protecting yourself with a wall of water. I've never seen one explode because they have relief valves.
Mom doesn't need to worry about a thing.
:thumbup: Thanks!