Phoenix Journal · LEV & Air Quality
Hot work is one of the largest single causes of serious fire in industry, and the fires it starts tend to be severe. Welding, cutting, grinding and brazing all throw heat, sparks and molten metal into a workshop, and a spark that lands unseen can smoulder for hours before it flares. A safe system of work is how you make sure that does not happen.
Hot work is any task that produces heat, sparks or a flame: welding, flame and plasma cutting, brazing, soldering, grinding and disc cutting, and torch work of every kind. Insurers consistently rank it among the biggest causes of workplace fire, and the losses are disproportionately large because the ignition is easy to miss. Molten sparks travel much further than people expect, roll into cracks and voids, drop through floor openings and get drawn into ductwork, where they can lodge in grease or dust and smoulder long after the tools have gone quiet.
Because the risk is both high and predictable, it is controlled with a formal safe system of work rather than left to the operator's judgement in the moment. In practice that means a permit-to-work system for any hot work carried out away from a purpose-built, fire-safe area. Where flammable or explosive atmospheres may be present, written procedures are effectively required under the dangerous substances regulations, and the HSE's guidance on permits to work is the benchmark against which a system's adequacy is judged if things go wrong.
The permit does the thinking
A hot work permit is not bureaucracy; it is a structured pause that makes someone confirm the hazards are dealt with before work starts. The first question it should force is whether the job can be done a safer way or moved into a designated fire-safe area, avoiding the permit entirely. Where it cannot, the permit drives the area to be made safe: combustibles cleared from a generous radius or screened where they cannot be moved, openings and duct entries sealed so sparks cannot travel, flammable liquids and gases removed, and fire extinguishers placed to hand. It confirms the equipment is sound, the ventilation or local exhaust is dealing with the fume, and, in a confined space, that the atmosphere has been tested, which usually means a confined-space permit alongside the hot work one.
The permit is time-limited and specific to the task and location, and it is signed by someone with the authority to issue it, not simply by whoever is holding the torch. That separation is deliberate: it puts a second, accountable pair of eyes on the controls before anyone strikes an arc.
Every permit should also name who is doing the work, who is issuing it and who is keeping the fire watch, so responsibility is never vague at the moment it matters most. Insurers take this seriously enough that many policies make a hot work permit system a condition of cover, so a fire started during unpermitted hot work can jeopardise the very claim meant to pay for it.
Two hazards, one job
Hot work carries a health hazard alongside the fire risk, and a system that controls one while ignoring the other is only half a system. Welding and cutting generate fume that is now treated as capable of causing cancer, so the safe system of work has to address extraction and ventilation at the same time as combustibles and fire watch. That is why the discipline of learning to manage welding fume beyond just buying extraction belongs inside your hot work planning: the same task that could start a fire is also loading someone's lungs, and a good permit process prompts you to control both rather than trading one risk for the other.
During and after
The control that gets skipped under time pressure is the one that matters most: the fire watch. A trained person, equipped with an extinguisher and free of other duties, should watch the work area and the spaces around it, above, below and the far side of walls, throughout the job and for a set period after it finishes, commonly at least an hour, because that is when a hidden smoulder finally shows itself. Only then is the permit closed and signed off. Hot work is one strand of the wider job of managing hazardous substances in a small engineering firm, and treating it with the same permit discipline, before, during and after, is what separates a controlled task from the one that quietly starts a fire two hours after everyone has gone home.
Questions
A permit is needed for hot work carried out anywhere other than a purpose-built, designated fire-safe area. Welding, cutting, grinding, brazing and soldering in a workshop bay, on site or in a plant room should run under a permit that confirms the area has been made safe and a fire watch is in place before work starts.
The fire watch should cover the whole job and continue for a set period after work finishes, commonly at least an hour and often longer for higher-risk work, because sparks can smoulder unseen before igniting. The watcher must be trained, equipped with an extinguisher and free of other tasks, and should monitor adjoining areas as well as the immediate one.
Ideally eliminate the hot work or move it to a designated safe area. Where that is not possible: clear or screen combustibles, seal openings and duct entries so sparks cannot travel, remove flammables, provide extinguishers, control the fume with ventilation, keep a fire watch during and after the work, and issue and close a permit signed by an authorised person.
Phoenix Duct Clean · by the numbers
Grease-laden extraction is a fire path a stray spark can find. Phoenix cleans ductwork and canopies to TR19 Grease, cutting the fuel that turns a spark into a fire. UK-wide.