CA Plumbing PrepC-36 License Exam Prep
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Trade Exam · Module 6

Hot Work Safety: Torches, Cylinders and Fire Watch

Lesson 3 of 8~20 minFree previewCurrent as of September 2026Leer en español

Soldering and brazing with a torch is hot work, and it is how many job site fires start. This lesson covers the Cal/OSHA rules for fuel gas and oxygen cylinders (valve end up, 20 foot oxygen separation, the 15 psi acetylene limit, no oil or grease on oxygen), fire extinguishers near fuel gas work, fire prevention before you light the torch, the fire watch and its half hour, ventilation for fumes, and eye protection shades.

Key Takeaways

  • Soldering and brazing with a torch fall under Cal/OSHA's gas welding and cutting orders, and the employer must have a fire prevention and suppression procedure (Title 8 Sections 4794, 4848).
  • Acetylene and fuel gas cylinders are stored and used valve end up, secured so they cannot fall, with valve caps on before they are moved (Section 1740).
  • Stored oxygen cylinders are kept 20 feet from fuel gas cylinders and combustibles, or separated by a noncombustible barrier at least 5 feet high with at least a one-half hour fire rating (Section 1740(g)).
  • Acetylene is not generated or used above 15 psi gauge, except acetylene dissolved in a solvent in an approved cylinder (Section 1743(b)).
  • Keep oil and grease away from oxygen cylinders, valves, regulators and hoses, and never handle them with oily hands or gloves (Section 1743(c)).
  • Keep a dry chemical or carbon dioxide extinguisher rated at least 10 B:C near work with bottled fuel gas (Section 1743(j)).
  • Move combustibles away or shield them before hot work; where a fire watch is required, federal OSHA requires it to continue at least a half hour after welding or cutting ends (29 CFR 1910.252(a)(2)(iii)).
  • Cylinders of oxygen, acetylene or fuel gas are never taken into confined spaces (Section 1740(b)).

Why Hot Work Deserves Its Own Lesson

Every time you sweat a copper joint or braze a line set with a torch, you are doing hot work next to wood framing, insulation, paper-faced drywall and dust. Cal/OSHA's gas welding and cutting orders expressly cover brazing and soldering done with gas and oxygen (Title 8 Section 4794(a)), so the same fire prevention and cylinder rules apply to a plumber with an air-acetylene or oxy-acetylene rig as to a welder.

The C-36 Safety section tests this with scenarios: a cylinder lying in a van, grease on a regulator, a flame in the insulation, a dizzy worker brazing in a crawlspace. The rules below give you the right answer to each.

Before You Light the Torch: Fire Prevention

  • The employer needs a procedure. Where gas welding, cutting, brazing or soldering is done, the employer must establish a fire prevention and suppression procedure and issue instructions based on ANSI Z49.1 and NFPA 51B, which Section 4848 incorporates by reference. On a real job this usually shows up as a hot work permit or checklist. Follow it.
  • Move the fire hazard or move the work. When practical, move the object to a safe place. If it cannot be moved, take movable fire hazards away. If some hazards cannot be moved, confine the heat, sparks and slag with guards or shields (29 CFR 1926.352(a) and (b)). If none of that can be done, the work should not be done (29 CFR 1910.252(a)(1)(iii)).
  • Know what 35 feet means. Under federal OSHA's general industry rule, a fire watch is required when appreciable combustible material is closer than 35 feet to the point of operation, when combustibles farther away are easily ignited by sparks, when wall or floor openings within 35 feet expose combustibles, or when combustibles sit on the other side of a metal wall or ceiling (29 CFR 1910.252(a)(2)(iii)(A)). That 35 feet is a distance for combustibles and fire watch decisions. It is not a rule about where the extinguisher goes.
  • Check the other side. Heat conducts through pipe, walls and floors. When you work on a wall, floor or ceiling, take the same precautions on the opposite side (29 CFR 1926.352(f)).
  • No flammable atmosphere. No welding,

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