Uh…think so. Don’t try it for yourself. R12 plus flame equals phosgene, aka, mustard gas, nerve gas.
Have..... many a time. Still here. Apparently you don’t have a clue about the old school leak detectors which were a simple propane bottle with a specialized adapter and hose. Still have that tool and use it from time to time.
Phosgene gas was a particularly nasty weapon used by the Germans in WW1 and has absolutely nothing to do with R-12 which, by the way, is the best and safest refrigerant ever developed.
And don’t even bother to throw that ozone layer BS at me.