What Is Hot Work?
Hot work is any task that produces flame, sparks, or heat capable of igniting flammable or combustible material — welding, cutting, grinding, brazing, and torch work. In oil and gas it is high-risk because of hydrocarbons and H2S, so it almost always requires a hot work permit before the job starts.
Examples of hot work
If a task can create an open flame, a spark, or enough heat to ignite something nearby, it counts as hot work — even when no flame is visible.
- Welding (arc, MIG, TIG, stick) and oxy-fuel cutting.
- Grinding, cutting wheels, and abrasive sawing that throw sparks.
- Brazing, soldering, and torch-applied work.
- Thawing pipe or applying heat with an open flame.
- Any spark-producing power tool used near flammable or combustible material.
Why hot work is high-risk in oil and gas
Hot work supplies the one element a fire or explosion needs that is otherwise hard to introduce: an ignition source. On a site with hydrocarbons, the fuel and air are already present, so a single spark can be enough. Vapors from tanks, lines, vessels, and even residue in "empty" equipment can reach a flammable concentration well away from the obvious source.
H2S adds a second hazard: it is toxic at low concentrations and flammable at higher ones, so the same atmosphere that can ignite can also be deadly to breathe. Because of this, hot work is rarely done alone — a dedicated fire watch monitors the area for sparks and incipient fires during the job and after it ends, ready to act before a smolder becomes a fire.
Hot work controls
Hot work is controlled through a hot work permit that documents the specific safeguards in place before the torch is lit. The permit ties the controls below to a defined location and time window, and is closed out when the job is done.
- Permit — a hot work permit authorizing the task, signed by a responsible person.
- Gas testing — atmospheric monitoring confirming the area reads below the action limit (commonly under 10% of the LEL) before and during the work.
- Fire watch — a trained watch with extinguishing equipment, kept during the job and for at least 30 minutes after it ends.
- Clear combustibles — remove or shield flammable and combustible material within the work area (NFPA 51B uses a 35-foot radius).
- Hierarchy of controls — eliminate or relocate the work to a safe area first; use a permit and PPE only when the hazard cannot be removed.
Hot work vs. cold work
Cold work is any task that does not introduce an ignition source — hand tools, bolting, manual valve operation, or work with non-sparking equipment. The line matters because hot work triggers the permit, gas testing, and fire watch requirements above, while routine cold work does not. When a job that started as cold work begins producing heat or sparks, it becomes hot work and the hot work controls apply from that point on.
Running hot work in the field? Log gas readings, fire watch, and sign-offs digitally — with a complete audit trail for every permit.
See hot work permit softwareFrequently Asked Questions
What is considered hot work?
Any task that produces flame, sparks, or heat that could ignite flammable or combustible material — welding, cutting, grinding, brazing, soldering, torch work, and spark-producing power tools used near a fuel source. If it can create an ignition source, it is hot work.
Does hot work always need a permit?
On oil and gas sites and other facilities with flammable atmospheres, hot work almost always requires a permit. The main exception is work done in a dedicated, fixed area designed and approved for hot work, such as a designated welding shop, where the standing controls already cover the hazard.
What is a fire watch?
A fire watch is a trained person assigned to monitor the hot work area for sparks and incipient fires, equipped with fire extinguishing means and the authority to stop the job. NFPA 51B requires the fire watch during the work and for at least 30 minutes after it is finished.
What is the difference between hot work and cold work?
Hot work introduces an ignition source — flame, sparks, or heat. Cold work does not, such as bolting, hand-tool work, or operations using non-sparking equipment. Hot work requires a permit, gas testing, and a fire watch; cold work generally does not. A cold-work job becomes hot work the moment it starts producing sparks or heat.