For anyone relying on any fire extinguisher I can attest to what a hopeless feeling you get when fire breaks out, you reach for your trusty extinguisher and.....
.....IT DOESN'T WORK!
It's happened to me twice in my life.
I can tell you that a "gauge in the green" on chemical extinguishers...
The most useful lesson I ever got from accomplished welders is that joint preparation is about 80% of getting good results.
In other words, spend most of your time getting everything set up before striking an arc.