I recently invested in a new Portaflame MAPP/Oxygen gas welder.
Results to date have been encouraging, and I am slowly improving my
technique. The only problem I have is that on shutting down, by
closing the torch controls for the MAPP and the oxygen a little at a
time in turn, I always end up with a loud and unsettling high-pitched
POP as the flame extinguishes. Can anyone give guidance on why this is
happening, and whether it is likely to cause damage/injury?
TIA.

CRB