Welding Near Gas Tank?

I always figured those custom exhaust guy are darn brave. Has anyone every taken an old Mpar (Chevies don't leak!?) to that guy with a small pinhole in top of the gas tank!???
Those guys have noses like a Radon gas detector. They smell some fume and send ya home...... or some just weld away!!
I have place wet rags over vented gas on truck and welded away.
Years ago I was back in my home town in W Ga visiting my old mom and looking for a project to haul back to Mo. I found the typical running 69 RR for$1000. I puled the tank and it had a couple of small pinhole in what was otherwise a sold tank. A guy I went to HS had a welding shop. I took the tank there and he put it over exhaust of running tractor while we partook of a cold one (or two). Then he brazed the holes shut. Yes the fumes dried out any gas fumes.
Some all it Southern enginuity, others just call it redneck! ha
Me, I always pull the tank now days. 99% of the time buy a new one and sender.