To avoid gas- or fume-related explosions, what must be done to tanks, pipes, and vessels before welding?

• A. Verify empty, thoroughly clean, inspect, and test for flammable residue
• B. Fill with water to extinguish residues
• C. Seal and seal again
• D. Skip unless the vessel is pressurized

Answer: (A)

Preventing gas- or fume-related explosions hinges on removing all sources of ignition by eliminating flammable residues and vapors before welding. The proper approach is to verify the vessel is empty, thoroughly clean it to remove hydrocarbons or other flammable material, inspect for any lingering residue or leaks, and test the atmosphere to confirm there are no flammable vapors present. If vapors remain, heat or sparks from welding can ignite them, even in a vessel that looks dry or empty.

Filling with water isn’t a reliable or practical way to neutralize residues and can create other hazards, including damage and steam pressure. Sealing the vessel would trap vapors rather than remove them. Skipping the preparation because the vessel isn’t apparently pressurized ignores the fact that flammable vapors can linger regardless of current pressure and can ignite once welding begins.