Lesson 3 of 5 · 3 min read
Hot work: welding, cutting and grinding
Sparks and hot slag start fires minutes after the torch is off. The watch stays through the work and after.
What counts as hot work
Hot work is any task that makes sparks, flame or heat: welding, cutting, grinding, brazing, soldering, thawing pipe, and torch-applied roofing. Sparks can travel, and hot slag can smolder in a crack or a wall cavity and flare up well after the work stops.
When OSHA requires a fire watch
Under OSHA 1910.252, a fire watch is required for welding or cutting wherever a serious fire could start, for example:
- Combustible materials are closer than about 35 feet to the work.
- Combustibles are farther away but easily ignited by sparks.
- Wall or floor openings could let sparks reach combustibles in nearby areas, including out of sight.
- Combustibles are against the other side of a metal wall, partition or roof and could ignite from conducted heat.
Construction sites follow a parallel rule, OSHA 1926.352.
Before, during and after
- Before: a hot work permit is issued, combustibles are moved away or covered with fire-resistant guards, and the right fire extinguisher is in reach.
- During: the fire watch stays the whole time, watching the work area and any spot where sparks could land, including the floor below and the far side of walls.
- After: the watch continues for at least 30 minutes once the work stops, to catch a smoldering fire. Many jurisdictions follow NFPA 51B and ask for 60 minutes or longer, and the fire marshal can extend it further for high-risk jobs.
The watcher's tools
The fire watch has a fire extinguisher and knows how to use it on a small, just-starting fire, and knows how to sound the alarm and call the fire department. Anything beyond a small fire means pull the alarm, get people out, and call 911.
Key points
- Hot work (welding, cutting, grinding, torch work) makes sparks and hot slag that start fires.
- OSHA 1910.252: a fire watch is required when combustibles are within about 35 feet or sparks could reach them.
- The watch stays through the work and at least 30 minutes after; NFPA 51B and the fire marshal can require longer.
- Watch the floor below and the far side of walls, not just the work itself.
Picture it
A contractor finishes welding a railing and starts packing up after 20 minutes. He asks if he's clear to go.
Not yet. OSHA wants the watch to continue at least 30 minutes after the work stops, longer if your permit or fire marshal says so. Keep watching the area, including where sparks fell and the far side of the wall, and note the clear time in the log before anyone leaves.
Resources
- OSHA: Welding, Cutting, and Brazing (Hot Work)
The federal safety topic page for hot work, with the fire prevention and fire watch requirements for welding and cutting.
- OSHA 1910.252: General requirements for welding, cutting and brazing
The standard itself: when a fire watch is required, the 35-foot rule for combustibles, and the at-least-30-minutes watch after the work stops.
- OSHA 1926.352: Fire prevention for welding and cutting (construction)
The construction-industry version of the hot work fire prevention and fire watch rules.