What is the 35-foot rule for hot work?

Where the number comes from

Sparks and slag from welding and cutting travel. Thirty-five feet is the radius the standards use for the zone in which they can be expected to land and ignite ordinary combustibles: paper, wood, cardboard, dust, insulation, fabric. Inside that radius, the standards want the combustibles gone or covered; where that is not possible, they want a person watching.

The three conditions that call for a watch

OSHA’s 29 CFR 1910.252(a)(2)(iii) names them. Combustibles within 35 feet of the work that cannot be moved. Combustibles further than 35 feet that are easily ignited by sparks, such as dust, lint or piled paper. Wall or floor openings within 35 feet that expose combustibles in adjacent areas, including concealed spaces in walls and floors. Any one of them makes a fire watch necessary, and the watch continues at least 30 minutes after the work is completed under OSHA and at least an hour under NFPA 51B.

Applying it on a real job

The permit authorizing individual walks the 35-foot radius before the torch is lit: what is on the floor, what is behind the wall, what is on the deck below, where the drains and scuppers go on a roof. Whatever can be moved is moved; whatever can be covered is covered with fire-resistant material; what remains is what the watch is for. The watch stands where the sparks go, not where the welder stands, and stays for the post-work period.

Price Protection’s part

Officers trained for hot-work fire watch stay through the work and the post-work period the permit sets, keep extinguishers at hand and sign the log for the permit file. The 35-foot rule article goes through the radius with examples, and the hot work fire watch page explains how a watch is booked. This is a summary, not legal advice.