Hot work permit

Hot work is any activity that generates a source of ignition: welding, oxy and plasma cutting, brazing, soldering, grinding and disc cutting, thermal lancing, bitumen and torch applied membranes, and heat guns on some materials.

The trigger for a permit is location rather than activity. Work in a designated hot work area, such as a properly set up workshop or welding bay with non combustible surroundings and fire protection, generally does not need a permit for each job. Hot work anywhere else does, because the controls have to be established fresh each time.

On a construction site that means essentially all hot work needs a permit, since almost nothing on site is a designated area. The highest risk versions are hot work on or near completed finishes, in roof and ceiling voids and service risers where sparks disappear out of sight, near flammable storage, on vessels and pipework that may have held something flammable, and in occupied buildings during refurbishment.

There is no model work health and safety regulation that names a hot work permit and requires one. The obligation comes from the general duty to manage risks so far as is reasonably practicable, and the standard that sits behind Australian practice is AS 1674.1, which deals with fire precautions for welding and allied processes. In practice two other forces make the permit compulsory: most principal contractors mandate it through their permit system, and most property insurers impose it as a condition of cover.

For a deeper look, read Permits to Work: The Control That Sits Above the SWMS.

The permit is the record that the controls were established before the work started, by someone competent to judge it.

The work and the location. What is being done, exactly where, and on what equipment or element.

The period. Start and finish times for the authorisation, not the shift. A permit that expires at a stated time forces a reassessment if the work runs over.

Combustible clearance. Combustible material removed or protected within the required radius of the work, with a distance commonly set at around 15 metres in Australian practice, and openings, penetrations, drains and gaps covered so sparks cannot travel into a void or a lower level.

Atmospheric testing where it applies. On vessels, tanks, pipework or any space that may contain flammable vapour, the atmosphere is tested before work starts and monitored as required.

Fire protection at the work. Extinguishers or a charged hose at the point of work, suitable for the material involved.

Fire detection isolation. Where smoke detection has to be isolated to avoid false alarms, the permit records the isolation, who authorised it, and crucially when it is restored.

The fire watch. Who is keeping it, during the work and for the specified period afterwards.

Sign off and closeout. The authorising person's signature, and a closeout confirming the fire watch was completed and the area was left safe.

The closeout is not administrative. It is the only evidence that someone looked at the area after the work stopped.

Most hot work fires are not discovered while the welder is working. They are discovered later, because a spark landed somewhere out of sight and smouldered. The fire watch exists for that gap.

The fire watch is a person, not a device, and their only job is watching for ignition. They cannot be the person doing the hot work, and they cannot be given another task at the same time.

Watch has to be kept during the work and for a period after it stops. Australian practice treats around 30 minutes as the minimum, many sites and insurers require 60 minutes, and longer periods apply where material can smoulder undetected or where the work was above or beside a concealed space. The permit should state the period rather than leave it to the crew.

Where sparks can fall to another level or into a void, the watch has to cover those places too, which often means a second person below. A watch kept only at the point of work misses the mechanism that causes most of these fires.

The watch also has to know what to do: how to raise the alarm, where the nearest extinguisher and hose are, and who to call. On a site with isolated detection, they are the detection system until it is restored.

A permit for the week. Conditions change daily. The permit covers this work, in this location, for this period.

The welder keeping their own fire watch. It is not possible to weld behind a helmet and watch the surroundings at the same time, and this is the single most common breach.

Leaving detection isolated. Isolating smoke detection and not restoring it leaves a building unprotected overnight. The restoration belongs on the permit with a time against it.

Ignoring what is on the other side. Sparks and conducted heat travel through penetrations, into risers and voids, and through a wall to combustible material stacked against the far face. Check both sides and below.

No closeout. An open permit with no completion sign off means nobody can say whether a fire watch was kept.

Using a SWMS instead. The safe work method statement describes how to do hot work safely in general. The permit authorises this job now, with these controls confirmed. Both are needed.

Forgetting the insurer. Policy conditions often specify the permit system, the fire watch duration and the clearance distances. Breaching them can affect cover even if nobody is hurt.