Welding, cutting and grinding start fires — the permit is how you stop them
Hot work — welding, flame cutting, grinding, brazing, soldering and anything else that makes flame, heat or sparks — can start a fire directly, by sparks travelling, or by heat conducting through metal, and combustibles can flare up hours later. Control it with a hot work permit that sets out the controls, a nominated fire watcher, combustibles cleared or protected within 10 m, and extra controls again if the work is in a confined space.
Hot work is any work that can ignite combustible materials or a flammable atmosphere: welding, flame or oxy cutting, disc cutting and grinding, brazing, soldering, gas torches and blow lamps, hot air guns, burning off, thawing pipes, and torch-applied roofing or flooring.
A purpose-built workshop area designed to contain the process is the exception — hot work there, for the purpose it was designed for, does not need a permit each time. Everywhere else, it does.
Ignition can happen three ways: the direct heat of the flame or arc; heat conducted through metal to fuel on the other side of a wall or bulkhead; and sparks, slag and hot debris travelling to a distant fuel source. Some materials can smoulder unseen and flare into open flame hours after the work has finished — which is exactly why the fire watch continues after the tools go down.
A hot work permit is authorised before the work starts, displayed at the site, and returned on completion. It records the controls in place — combustibles removed or protected, openings covered, draughts eliminated, screens and signage up, extinguishers to hand, and the fire watch arranged. It is part of a wider permit-to-work system for high-risk tasks, and the work should be supervised by someone responsible for its safe execution.
| Stage | Controls |
|---|---|
| Before | Remove or protect combustibles within 10 m; cover floor and wall openings within 10 m; eliminate cross-draughts; barricade and sign; check the atmosphere; have extinguishers ready. |
| During | A nominated fire watcher on station; spark and flash screens; the right PPE for fume, UV, noise and burns. |
| After | Keep watch after the work finishes — WorkSafe says at least 30 minutes, and industry and insurer guidance often recommends monitoring for up to 2 hours, because materials can flare later. Inspect the work and adjacent areas, including the other side of walls and the floors above and below. |
Hot work in a confined space is far more dangerous. It adds the risk of asphyxiation — oxygen displaced by shielding gases such as argon, or carbon monoxide from engines — along with toxic fume and a flammable or explosive atmosphere. An oxygen-enriched atmosphere, above 23.5%, sharply increases the fire and explosion risk. This work needs a confined space entry permit and a trained stand-by person on top of the hot work permit. See confined spaces.
Fire is not the only risk. Welding and cutting expose workers to fume and gas, intense ultraviolet light (which causes arc eye and is linked to a rare eye cancer), high noise, burns and electric shock. Manage these with good ventilation and the right protective equipment. See PPE requirements and hazardous substances.
Capture your hot-work hazards and document the controls in one place. Book a demo and we'll show you how it works — free 30-day trial included.
Any work that can ignite combustibles or a flammable atmosphere — welding, flame or disc cutting, grinding, brazing, soldering, gas torches, hot air guns, burning off and torch-applied roofing.
An authorisation issued before hot work starts, displayed at the site and returned on completion, that records the controls in place — combustibles cleared, openings covered, screens up, extinguishers ready and a fire watch arranged.
WorkSafe says at least 30 minutes after the work finishes. Industry and insurer guidance often recommends monitoring for up to 2 hours, because smouldering materials can flare into flame later.
It adds asphyxiation, toxic fume and flammable-atmosphere risks, and an oxygen-enriched atmosphere increases the danger. It needs a confined space entry permit and a trained stand-by person on top of the hot work permit.
Combustibles within 10 metres should be removed or protected, and floor and wall openings within 10 metres covered, to stop sparks and heat reaching fuel.
