BE CAREFUL. BE EXTRA SAFE. DON'T BREATHE IN ANY FUMES EVER. DON'T GET IN A HURRY AND SKIP ANY SAFETY PRECAUTIONS. USE A RESPIRATOR IF YOU ARE NOT POSITIVE YOU ARE AVOIDING THE FUMES.
Step 1: Vaporize the Coating
1. Heat the EMT to vaporize as much of the galvanized coating as possible. I use a MAPP torch (I don't know if propane would work.) to thoroughly heat the area(s) where I will be welding. Do this outside. The galvanized coating will vaporize and leave a brown residue
Step 2: Grind the Surface
2. Grind the area that you heated. I use a flap-pad in an angle grinder, a wire wheel in an electric drill or an abrasive paint remover for this step. Do this outside. The result is a bright and shiny steel surface (Photo #2 below the yellow line)
Step 3: Move the Air While Welding
3. Weld with a fan (usually on the low setting) gently moving air over and away from the weld zone. Do this outside. Move the fan around until the air flow moves the fumes away but doesn't blow the shield gas away from the weld arc. This position can change depending on whether it is windy or calm outside.