As I have repeatedly said, the fire extinguisher in an RV is there for only one purpose: To keep the insurance company happy.
If a fire starts, and that one extinguisher won't put it out, GET OUT, STAY out, and call 9-1-1!
Anything you forgot to grab on your way out (except for the wife and kids) is done for, DO NOT go back!
If you are driving a motorhome, and the engine catches fire, DO NOT lift the doghouse! GET OUT! A motorhome will be reduced to nothing but a frame literally in MINUTES, probably long before the fire department gets there.
Remember, there are probably bombs in there! Spray cans, lantern fuel, bottles of cooking oil, fuel tanks, tires, etc. RUN AWAY!