NFPA 51B: Hot Work Fire Prevention

NFPA 51B, Standard for Fire Prevention During Welding, Cutting, and Other Hot Work, lays out how to control fire risk from hot work. OSHA's welding and cutting rules refer to it as good practice, and many insurers, fire codes and contracts require it.

• Welders
• Supervisors
• Safety Managers

Roles

• Permit Authorizing Individual (PAI): inspects the area, checks precautions and signs the hot work permit.
• Hot work operator: the person doing the welding, cutting or other hot work. Must be trained and follow the permit.
• Fire watch: trained person who watches for fires during and after the work. See Fire Watch Duties.
• Management must set up the program and make sure the roles are filled.

Key requirements (summary)

• Designated areas or permits: hot work is done in a safe designated area (a welding shop) or under a hot work permit. See Hot Work Permits.
• Move or protect combustibles within 35 feet of the work (11 meters). If they cannot be moved, cover them with fire-resistant blankets or shields.
• Cover or close openings, cracks and floor holes where sparks could fall. Protect floors and walls that could ignite or conduct heat.
• Do not do hot work where flammable vapors, gases or dust are present or in contact with flammable liquids. Test for flammable gas where needed.
• Have suitable fire extinguishing equipment ready. See Fire Extinguishers.
• Provide a fire watch during and for at least 30 minutes after the work, and monitor the area further, for example up to 3 hours after in certain cases, as required by the edition.
• Check sprinklers, alarms and detectors; do not impair them without proper steps. See Fire System Impairments.
• Special rules apply to hot work on containers, in confined spaces, on roofs and in occupied buildings. See Occupied Building Hot Work.
• Train employees and keep records.

Checklist for hot work

• Permit issued and posted
• 35-foot area cleared or protected
• Gas testing done if needed
• Extinguisher and fire watch in place
• Alarms and sprinklers working
• Post-work watch completed and signed off

Last updated: October 8, 2026