A hot work permit is a written authorisation that controls work producing heat, sparks or flame, such as welding, flame cutting, grinding and brazing. It names who does the work, the exact location and time limits, and the fire precautions needed before, during and after. The Joint Code of Practice on construction site fire safety calls for a continuous fire watch for at least one hour after hot work ends.
Hot work can cause fires that start after everyone has gone home. A spark drops into a cavity, smoulders for an hour, and the building is alight by the evening. A hot work permit exists to stop that happening.
What counts as hot work?
Hot work is any task that produces flames, sparks or enough heat to ignite materials nearby. Common examples include:
- welding (arc, MIG, TIG and gas)
- flame cutting and oxy-fuel work
- brazing and soldering with a torch
- angle grinding and disc cutting
- torch-on roofing
- using tar boilers and other heated equipment
Grinding and disc cutting catch people out. There is no flame, so they do not feel like hot work, but the stream of hot particles can travel well beyond the work area and land in places nobody is watching.
Why hot work needs a permit
A permit forces a pause before the work starts, so someone competent checks that the area is safe, the precautions are in place and everyone knows who is responsible. Hot work is risky for three reasons:
- Sparks and heat travel. They pass through gaps in floors, along ducts and into wall cavities. Heat also conducts through metal and masonry, which is why the far side of a wall or floor has to be checked before work starts.
- Fires smoulder. Dust, insulation and packaging can smoulder unseen and only burst into flame long after the work has stopped.
- Residues explode. HSE has warned that drums and containers which look empty can hold enough residue in seams and folds to form an explosive vapour when heated. Its safety alert on cutting drums followed two fatal accidents.
A permit is one part of a wider permit-to-work system. If you need the general principles of how permits are issued, accepted and handed back, see our guide to permit to work systems. This article focuses on the controls specific to hot work.
Is a hot work permit a legal requirement?
No UK regulation uses the words “hot work permit”, but the law requires the controls a permit delivers. Three sets of duties apply:
- The Regulatory Reform (Fire Safety) Order 2005 requires the responsible person to assess fire risk and put general fire precautions in place. Hot work is an obvious ignition source, and it should appear in your fire risk assessment.
- The Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) require ignition sources to be controlled wherever flammable substances or dusts are present. HSE’s Approved Code of Practice L137 covers safe maintenance, repair and cleaning under DSEAR, including work that introduces heat.
- The Management of Health and Safety at Work Regulations 1999 require a suitable and sufficient risk assessment.
HSE guidance has long said that introducing an ignition source such as welding, cutting or grinding where flammable materials may be present should be controlled through a permit-to-work system. On construction and renovation sites, the Joint Code of Practice on the Protection from Fire of Construction Sites and Buildings Undergoing Renovation, published by the Fire Protection Association and produced by RISCAuthority, sets out detailed hot work requirements. Insurers may make compliance a condition of cover, so check your policy.
Can you avoid hot work altogether?
Often, yes, and it should be the first question asked. The Joint Code says alternative methods should be adopted where possible, and HSE’s alert on drums and tanks points out that in many cases hot work may not be necessary. Options include:
- cold cutting with hydraulic shears, saws or pneumatic chisels
- bolted, clamped or push-fit joints instead of welded or soldered ones
- replacing a damaged tank or drum instead of repairing it
- moving the item to a dedicated hot work area or workshop away from combustibles
This is the hierarchy of control in practice: removing the hot work beats controlling it.
What should a hot work permit include?
A hot work permit should cover one specific task in one specific location. A good permit records:
- The task: exactly what work is being done and with what equipment
- The location: the precise area, including floor, room or grid reference
- Time limits: the date, start time and expiry time
- The people: the issuer, the person carrying out the work and the fire watcher, each named
- Pre-work checks: combustibles removed or protected, openings sealed, the far side of walls and floors checked, detection and alarm arrangements confirmed
- Fire protection: type and number of extinguishers at the work area
- Other permits or isolations: for example, gas testing in a confined space or isolation of a flammable process
- Fire watch: who is doing it and for how long after work stops
- Sign-off: confirmation that the work is complete, the fire watch has finished and the area is safe
Who issues and signs a hot work permit?
Each role on a permit carries a separate responsibility. Where possible, the person issuing the permit should not be the person doing the work.
| Role | Responsibility |
|---|---|
| Permit issuer (authorised person) | Competent person authorised by the organisation to issue permits. Inspects the area, sets the precautions, signs the permit and signs it off at the end. |
| Permit holder (receiver) | The person carrying out or directly supervising the hot work. Reads and accepts the permit, follows the precautions and stops work if conditions change. |
| Fire watcher | Trained person who watches the area during the work and for the full fire watch period afterwards, with an extinguisher to hand and a means of raising the alarm. |
| Senior manager | Audits completed permits. The Joint Code requires completed permits to be inspected regularly (at least monthly) by a senior member of the project staff, with the inspections recorded. |
Contractors doing hot work on your premises should work under your permit system, not their own. Your site knows where the combustibles, voids and alarms are; a visiting welder does not.
How long should a fire watch last after hot work?
The Joint Code of Practice (10th edition, section 16.15) sets these minimum periods. It is written for construction sites and buildings undergoing renovation, but it is a sound benchmark for hot work elsewhere.
| Stage | Minimum requirement |
|---|---|
| During the work | Continuous fire watch, including during lunch and tea breaks and any other pause in the work |
| First hour after completion | Continuous fire watch for at least one hour after the work is completed |
| Second hour | Further checks at intervals of no more than 20 minutes for at least another hour |
| Higher-risk situations | Checks for up to three hours or more where the risk assessment calls for it, for example near timber frame, in high-rise buildings or where there are hidden voids |
Source: Joint Code of Practice on the Protection from Fire of Construction Sites and Buildings Undergoing Renovation, 10th edition, sections 16.15 and 16.16.
The Code also recommends routine use of thermal imaging cameras to find hot spots. It requires a fire check at the end of each working day or shift, particularly where hot work has taken place, so plan the work to finish with enough time left for the fire watch before the site closes.
Some organisations set their own periods in their hot work procedures, and insurers may set others. Where they differ, follow the longest that applies to you.
How long is a hot work permit valid?
For one task, one location and one work period. The Joint Code says permits must cover specific, identified activities and locations, must be signed off at the end of each work period, and should not be issued for long periods. It gives the example that a fresh permit should be issued if work runs from the morning into the afternoon, and says blanket permits covering several days must not be allowed.
Hot work permit checklist
Use this as a starting point and adapt it to your site.
Before work starts
- Is hot work really necessary, or is there a cold alternative?
- Have combustible materials been removed, or covered with fire-resistant blankets or screens?
- Have gaps in floors, walls and ducts been sealed or covered?
- Has the far side of walls, floors and ceilings been checked for combustibles?
- Has any container, pipe or tank been confirmed free of flammable residue?
- Are suitable extinguishers at the work area? The Joint Code calls for at least two, including a water or foam extinguisher rated at least 13A.
- Have screens been put up to protect other people from sparks and glare?
- Have fire detection arrangements been agreed, so a detector isolated for the work is not forgotten afterwards?
- Is the fire watcher named, trained and present?
During the work
- Is the fire watch continuous, including breaks?
- Is work stopped if conditions change, such as a new delivery of materials into the area?
After the work
- Has the full fire watch period been completed?
- Have any isolated detectors been reinstated?
- Has the permit been signed off and filed?
Your fire marshals should know when hot work is under way in their area. Our guide to fire marshal duties covers their wider role.
Frequently asked questions
What is a hot work permit?
A hot work permit is a written authorisation for work that produces heat, sparks or flame, such as welding, cutting or grinding. It names who is doing the work, where and when, and sets out the fire precautions to take before, during and after the work, including the fire watch.
Does grinding count as hot work?
Yes. Angle grinding and disc cutting throw hot particles that can ignite combustible materials some distance away, so they should be controlled in the same way as welding and flame cutting.
How long should a fire watch be after hot work?
The Joint Code of Practice on construction site fire safety calls for a continuous fire watch for at least one hour after the work is completed, followed by checks at least every 20 minutes for a further hour. Higher-risk work may need checks for three hours or more.
Who can issue a hot work permit?
A competent person who has been authorised by the employer or site management to issue permits. They should understand the hazards of hot work and the site, and ideally should not be the same person who carries out the work.
How long is a hot work permit valid for?
For a single task in a single location during one work period. The Joint Code of Practice says permits should be signed off at the end of each work period and that blanket permits covering several days must not be allowed.
Where to learn more
- Permit to Work Training: one-day General or two-day General and Specific course, with hot work permits on the two-day course
- Fire Marshal and Fire Warden Training: for the people who lead evacuation and support fire checks
- DSEAR Training: dangerous substances, explosive atmospheres and hazardous area zoning
- Permit to work systems: a UK guide
- DSEAR 2002 explained
Talk to KeyOstas
Our Permit to Work course trains the people who write, issue and authorise permits, including hot work permits on the two-day option. We deliver it at your site for up to 12 delegates.
Send an enquiry or call +44 (0)330 056 9534.