Welding in Confined Spaces

Welding in a tank, pipe, vessel or pit combines two high-risk jobs: confined space entry and hot work. Fumes and shielding gases collect, oxygen can fall, fires can start, and escape is slow. Both sets of rules apply together.

• Welders
• Confined Spaces
• Fire Watch

What makes it dangerous

• Welding fumes and gases build up where air does not move. See Welding Fume & Manganese.
• Shielding gases such as argon and carbon dioxide displace oxygen. See Inert Gas Asphyxiation.
• Fire and explosion from flammable vapors, residues and coatings.
• Electric shock in wet metal spaces, with a worker in contact with the metal.
• Heat stress in tight metal spaces.
• Hard escape, which complicates rescue. See Confined Space Rescue.

Before entry

• An entry permit and a hot work permit are issued and reviewed. See Hot Work Permits
• The space is isolated, lockout applied, cleaned and purged of flammables as needed
• The atmosphere is tested for oxygen (19.5 to 23.5 percent), flammable gas and toxic gases, and monitored continuously during welding
• Forced ventilation and local exhaust remove fumes at the source and bring in clean air
• An attendant stays outside and keeps contact with the entrants
• A rescue team or method is ready before anyone enters

Equipment rules

• Keep gas cylinders and welding machines outside the space (1926.353 and 1910.252). Run hoses in.
• When leaving the space for a break, shut off the gas at the cylinder or a safe point outside and remove torches so gas cannot leak in. Disconnect electrode holders and turn off the power.
• Use insulated electrode holders, dry gloves and a dry work position. Use a manual-lift or auto-shutoff device where the rules require.
• Ground the work properly, with the return cable close to the work.
• Use a retrieval line and harness when vertical entry is needed, unless that would add hazard.
• Provide a fire watch with an extinguisher during and after the work.

Respiratory protection

Fume and gas levels may still be too high even with ventilation. Respirators or supplied-air may be needed. See SCBA & Supplied-Air Respirators.

Last updated: October 8, 2026