Hot works fire risk: permits, fire watch and after hours

What is hot work, and why is it a fire risk?

HSE defines hot work as any process that generates flame, sparks or heat. Common types include oxy-fuel heating, cutting and welding, grinding and cutting metal, torch-applied roofing, heat guns and soldering irons.^[1]

The danger is not only at the torch. Sparks and heat travel into voids, through gaps in walls and floors, and onto material below. HSE notes that some combustible materials can smoulder for a significant period after work has finished before they ignite.^[1] HSE also estimates there are hundreds of fires on construction sites each year.^[1] Hot work happens on construction and refurbishment sites, in factories and workshops, and during maintenance on industrial sites.

Seven precautions for hot work

Drawn from HSE guidance and the FPA's Joint Code of Practice. Always follow your own risk assessment, your principal contractor's rules and your insurer's conditions.

1. 1

   Design it out or use a cold method

   HSE guidance says hot work should be designed out where practicable and replaced with cold methods, and the need for it justified by a risk assessment.^[1] The Joint Code also says alternatives should be used where possible.^[4]

2. 2

   Issue a permit for the specific job

   Where hot work cannot be avoided, a hot work permit controls it. The Joint Code says permits must cover specific, identified activities and locations, be signed off at the end of each work period, and never be blanket permits over several days.^[4] HSE explains how permit to work systems control high-risk jobs.^[3]

3. 3

   Clear and protect combustibles

   Remove loose combustible material from in and around the work area, from breaches in walls, floors and ceilings, from beneath the work and from the other side of any wall or partition. Protect anything that cannot be moved with non-combustible board.^[1]

4. 4

   Have extinguishers to hand

   At least two suitable fire extinguishers should be within reach of the hot work and of any fire watch position.^[1][4]

5. 5

   Watch during the work and through breaks

   Keep a careful watch for fire while the work is going on, and keep the fire watch going when people take breaks, including areas on the other side of walls, floors and ceilings that cannot be seen from the work.^[1]

6. 6

   Keep a fire watch after the work ends

   HSE guidance calls for a continuous fire watch for at least an hour after hot work ends, then at least one more check two hours after the end.^[1] The FPA says further checks should then be made at intervals of no more than 20 minutes, in some cases for three hours or more based on risk assessment.^[5]

7. 7

   Finish early, then close the permit

   HSE guidance says hot work should be completed two hours before the end of the working day, because some materials smoulder for a long time before they ignite. Close the permit after a visual inspection of the area.^[1]

Where existing CCTV fits in

The permit, the fire watch and extinguishers come first. Once the fire watch has ended and the site empties, the cameras already on site may still be able to see hot work areas, skips and material stores.

Where a camera has a clear view, Woodcock AI can watch it for smoke and flame and send an alert with the clip to the people you choose, by app push notification, email or SMS. Alerts to a monitoring centre (ARC) and phone-call alerts are available as optional add-ons. It works on existing cameras, and what each camera can see, and which detections are supported, is confirmed in a free site assessment. It complements, and does not replace, the fire watch, the permit or certified fire detection and alarm systems. See how it works in the guide to video smoke detection on existing CCTV.

What a smoke alert looks like

This is a real night-time infrared frame from an existing camera, with smoke picked out. It is from a yard, not a hot work job, but it shows the kind of view an alert is built from.

Hot work checklist

Tick off each item for the job in hand. Progress is saved in this browser only. This checklist summarises the guidance above; it is not a permit.

• Cold method considered first and ruled out
• Permit issued for this job and location only
• Combustibles cleared, including below and behind walls
• Remaining combustibles protected with non-combustible board
• Two suitable extinguishers within reach
• Fire watch through the work and every break
• Continuous fire watch for at least an hour after
• Further check at two hours, longer if the risk assessment says so
• Hot work finished two hours before the end of the day
• Permit closed after a visual inspection

0 of 10 done

Running a waste or recycling site? See the fire prevention plan checklist.

Sources

This guide is general information, not professional fire safety advice. Check the current editions of these documents.

1. HSE, HSG168 Fire safety in construction (third edition). Defines hot work, sets out precautions before, during and after, the fire watch and finishing hot work two hours before the end of the working day. Last checked 23 October 2026.
2. HSE, Process fire risks (construction). Clearing combustibles, suitable extinguishers, a careful watch, and permits to work on larger projects. Last checked 23 October 2026.
3. HSE, Permit to work systems. What a permit to work is and how it controls high-risk jobs. Last checked 23 October 2026.
4. FPA and partners, Joint Code of Practice: Fire Prevention on Construction Sites (tenth edition). Section 16 on hot work: permits for specific activities and locations, no blanket permits, clearing combustibles, extinguishers and the fire watch. Last checked 23 October 2026.
5. FPA, RC7 Recommendations for hot work. Fire watch for at least an hour after work, then further checks at intervals of no more than 20 minutes, in some cases for three hours or more based on risk assessment. Last checked 23 October 2026.