Grinding & Cutting Sparks

Sparks and slag from welding, torch cutting and grinding can fly 35 feet or more, bounce, roll, and drop through cracks into spaces you can’t see. Many hot work fires start smoldering and don’t break out until long after the crew has gone home.

• Welders & fabricators
• All trades
• Maintenance

The 35-foot rule

• Move combustibles at least 35 feet away from hot work, or protect them with fire-resistant covers, guards or shields.
• Cover or close openings, cracks and holes in floors and walls within that distance, so sparks can’t fall through.
• When combustibles can’t be moved or protected, don’t do the hot work there.

Where sparks hide

• Floor openings, pipe chases and gaps around penetrations
• Ductwork and ventilation openings
• Wall cavities, insulation and roof assemblies
• Piles of rags, cardboard, sawdust and trash
• Wood framing, decking and pallets
• The other side of a wall or floor you’re cutting through

Fire watch

• A fire watch is required when combustibles are within 35 feet or openings could carry sparks elsewhere.
• The fire watch has an extinguisher, knows how to sound the alarm, and watches only for fire.
• OSHA requires the watch to continue for at least 30 minutes after hot work ends. NFPA 51B and many insurers now call for at least 60 minutes, with more monitoring afterward.

Controls

• Use welding blankets and spark-containment curtains rated for the job.
• Wet down combustible floors where allowed (watch for shock hazards near electrical work).
• Aim grinder and saw sparks downward and away from combustibles and people.
• Get a hot work permit where required. See Hot Work Permits.

Last updated: October 2, 2026