What Is a Hot Works Permit? When You Need One and What It Covers

A hot works permit is a written authorisation for one hot job, in one place, for a set time. It lists the precautions that must be in place before anyone lights a torch or starts a grinder, and it names who checked them. HSE's construction guidance says to use a formal system like this wherever hot work can't be avoided. Someone with authority on the site or in the building issues it.

No law requires a hot work permit by name. But fire and construction law do make you control the risk, and HSE points to a permit as the way to do it. The part of the permit that matters most is the fire watch after the work stops. That's when a hidden fire shows itself.

What is hot work?

HSE defines hot work as any process that generates flame, sparks or heat. Its construction guidance, Fire safety in construction (HSG168), gives these common examples.

• welding, cutting and heating with oxy-fuel gas
• grinding and cutting metal with power tools
• torch-applied roofing, such as torch-on felt
• heat guns
• soldering irons

The risk travels further than the job. HSE's welding guidance warns that heat, sparks and drips of molten metal and slag can travel a long way and start fires in the next room. HSG168 adds that structural steel, pipework and ducting can carry heat into the next room and set fire to anything combustible touching them.

HSE's first choice is to avoid hot work altogether. Its own example is a push-fit pipe joint instead of a soldered one.

The law behind a hot work permit

No UK regulation is called a hot work permit, and none says every hot job needs one. The duty to control the fire risk is legal, though, and it comes from several laws.

The Regulatory Reform (Fire Safety) Order 2005 covers England and Wales. Its duties fall on the "responsible person", which is the employer, or whoever controls the premises. They must assess the fire risk and take general fire precautions. HSE says that on a construction site the responsible person will usually be the main or principal contractor. For the wider workplace fire duties, see the guide to fire marshals and the Fire Safety Order.

In Scotland, the Fire (Scotland) Act 2005 does the same job. Employers must assess the fire risks to their staff. Anyone who controls premises must assess the risks to the people in them and act on what they find.

On construction work, regulation 29 of the CDM Regulations 2015 adds a specific duty. Suitable and sufficient steps must be taken to prevent, so far as reasonably practicable, the risk of injury from fire or explosion.

Where flammable gases, vapours or dusts could be present, the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) apply. Of the laws behind hot work, DSEAR is the one that names permits. DSEAR's general safety measures include a system of permits to work for hazardous places and hazardous activities. Each permit is issued before the work starts, by someone responsible for that job.

HSG168 says that where you can't avoid hot work, you should use a formal system such as a permit to work. On high-risk sites, such as timber frame or high-rise buildings, it says hot work should run under a strict permit system controlled by the principal contractor. A fully documented permit may not be needed where the risk is low, such as in a designated hot work area. Even then, HSE still expects an extinguisher and a fire watch.

So a permit isn't a legal document in its own right. It's the way HSE expects you to show you've met duties that are.

What goes on a hot work permit

HSG168 says a permit system should normally record these points.

• where the hot work will happen and what it involves
• when it will start and how long it should take
• how long the permit stays valid
• the precautions before, during and after the work, including the fire watch
• how to raise the alarm
• who is in direct control of the work
• who authorised the permit and who will close it

HSE's permit-to-work guidance adds that the people doing the job sign the permit. Their signature shows they understand the risks and the precautions.

A permit covers one clearly defined job, for a set time. HSE says it shouldn't give blanket permission for hot work anywhere on site at any time. It also says the permit, by itself, doesn't make a job safe.

The precautions before, during and after hot work

Before the work, HSG168 expects someone to visit the area. That matters most in refurbishment, where nobody may know what's inside the walls.

• Remove loose combustibles from around the work, from below it and from the far side of any wall or partition you're working on.
• Clear combustibles out of gaps in walls, floors and ceilings where sparks or heat could get in.
• Cover anything that can't be moved, and any openings, with non-combustible board.
• Put at least two suitable fire extinguishers within reach of the work and of the fire watch.
• If part of the fire alarm or detection has to be isolated, agree how it gets switched back on at every break and at the end of the day.

In an occupied building, HSE also says the work mustn't interfere with escape routes, fire separation, alarms, dry risers or sprinklers.

During the work, someone keeps a careful watch for fire. HSG168 says that watch carries on through breaks. It also covers any area on the other side of a wall, floor or ceiling the work might reach, because a fire can start where you can't see it.

How long should the fire watch last after hot work?

HSE gives two different figures in two places.

HSE source	Setting	Fire watch after hot work stops
HSG168, Fire safety in construction	Construction sites	A continuous watch for at least an hour, then at least one more check two hours after the work ends
Safety risks from welding	Welding outside a safe area, or where combustibles can't be removed	At least 30 minutes, extended to 60 where a fire could be slow to develop or hard to spot

HSE guidance checked 26 October 2026.

On a construction site, plan for HSG168's hour and two-hour check, and write the time on the permit. HSG168 accepts a different procedure only where a suitable and sufficient risk assessment clearly shows the fire risk is minimal.

HSG168 explains why the watch runs on. Some materials smoulder for a long time before they catch. That's why it says all hot work should finish two hours before the end of the working day, so there's time for the fire checks.

The fire watcher needs to be able to act. HSG168 says workers should be told how to use extinguishers, how to raise the alarm and how to do a fire watch, and for how long. For the extinguisher and emergency side, the Fire Marshal course covers fire prevention and emergency procedures.

The permit closes only after a final look at the area. HSG168 says that closing check should include any images from the fire watch, such as thermal images.

Who issues a hot work permit, and who works under it

Systems differ between sites, but HSE sets the general rules.

Only people with clearly assigned authority should issue or close a permit. They need enough information about the job to spot the hazards and choose the precautions. On a construction site, the principal contractor has to work out with the hot works contractor how the job affects the site's fire precautions.

HSE's permit-to-work guidance describes separate roles. One person issues the permit. Another accepts it for the people doing the work. On a small site, one person may cover several of those roles.

If the job runs into another shift, HSE expects a handover. The incoming shift needs to know about the open permit, and HSE recommends the incoming issuer signs to let it continue.

Hot work training for workers and supervisors

HSG168 says workers who carry out or supervise higher-risk work must understand the hazards and know how to react to a fire. The contractor or person in charge must make sure they understand how to follow a permit where one is used.

We run Hot Works Awareness, an online CPD course. It covers spotting hot work and its fire risks, prevention and control measures, basic hot work risk assessments and permit-to-work procedures.

A permit is only paperwork until someone watches the area after the torch goes out. For the training duties that sit behind that, see health and safety training for employees.

Frequently asked questions