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📋 Toolbox Talk · Health & Safety

Hot Works:
The Fire That Starts After You Leave

Permits, fire watch and the hour after you finish — why most hot works fires start once the tools are packed away.

✅ Verified August 2026📚 HSE · Fire Safety Order 2005🇬🇧 Applies across the UKukworkrights.co.uk

The risk

Why hot works cause major fires

Hot works means welding, cutting, grinding, brazing, soldering, hot air stripping and using open flame
Sparks from grinding and cutting can travel ten metres or more and stay hot enough to ignite
Sparks can drop through gaps, cable holes and floor voids and land somewhere nobody is watching
Heat conducts through metalwork and can ignite material on the other side of a wall
Most hot works fires are discovered after the work has finished, from smouldering that took time to develop
Hot works are one of the leading causes of serious commercial and construction fires in the UK
Insurers frequently exclude cover where a permit system was not followed

⚠ The fire usually starts after you've gone

Smouldering material can take an hour or more to develop into a fire. That is exactly why the fire watch continues after the tools are packed away, not just during the work.

The controls

Permit, prepare, watch

Avoid hot works where you can — cold cutting, bolting or pre-fabrication removes the risk entirely
Where unavoidable, work under a hot works permit issued by a competent person and valid for a defined time and place
Clear combustibles within at least ten metres, or protect them with fire blankets and screens
Check for hidden risks — voids, ducts, cavities, insulation, and what is on the far side of the surface
Isolate or protect detection systems if needed, and remember to reinstate them
Have the right extinguisher immediately to hand and someone who knows how to use it
Maintain a fire watch during the work and for a defined period after it stops — commonly at least 60 minutes, longer for higher risk
Final check of the area before leaving, including adjacent rooms and the floor below

The permit closes when the watch ends

A permit is not finished when the welding stops. It closes when the fire watch has completed and someone competent has checked the area and signed it off.

Your rights

What you can insist on

To work under a proper permit system rather than informal arrangements
Adequate time to clear the area and set up protection before starting
Correct PPE free of charge — eye and face protection, flame-resistant clothing, gloves
Fume control — welding fume is a carcinogen and requires extraction, not just ventilation
Not to be left alone to do the fire watch and the work at the same time
To stop work where you reasonably believe there is serious and imminent danger — Employment Rights Act 1996 s.44 and s.100

Welding fume is now treated as a carcinogen

HSE strengthened its position on mild steel welding fume: all welding fume can cause cancer, and engineering controls such as local exhaust ventilation are required for indoor welding, with RPE where LEV cannot control it fully.

Common questions

Frequently asked questions

How long should a fire watch last after hot works?

Practice varies with risk, but a minimum of 60 minutes after the work stops is common, and many permit systems require longer where combustibles or voids are involved. The permit should state the period, and the area should be re-checked before the permit is closed.

Do I need a permit for grinding?

Usually yes. Grinding produces high-energy sparks that travel and ignite, so most hot works permit systems cover grinding alongside welding and cutting. Check your site rules, but treat grinding as hot works unless you have been told otherwise in writing.

Is welding fume really dangerous?

Yes. HSE now takes the position that all welding fume, including from mild steel, can cause cancer. Indoor welding requires engineering controls such as local exhaust ventilation, with suitable respiratory protection where LEV cannot control exposure adequately.

For whoever runs this talk

Delivery notes & attendance record

Suggested length: 10 minutes. A toolbox talk is a short briefing on one hazard, given by a supervisor to the crew doing the work.

Before you start

The message that changes behaviour is the fire watch. Most hot works fires are discovered well after the work finished, from smouldering that nobody stayed to spot. Insist on the post-work watch period as a hard rule.

Questions to ask the team

What hot works are planned today, and is there a permit for them?
What is combustible within ten metres of where you'll be working, including behind the wall?
Who is doing the fire watch, and for how long after the work stops?
Where is the nearest extinguisher, and is it the right type?

The law behind this talk

Regulatory Reform (Fire Safety) Order 2005; Management of Health and Safety at Work Regulations 1999 reg. 3; Construction (Design and Management) Regulations 2015; Health and Safety at Work etc. Act 1974 s.2

Employers must give workers comprehensible information, instruction and training on the risks they face — Health and Safety at Work etc. Act 1974 s.2(2)(c) and Management of Health and Safety at Work Regulations 1999 reg. 10. Keep the record below as evidence that you did.

Attendance record

Topic	Hot Works: The Fire That Starts After You Leave
Date
Site / location
Delivered by
Actions agreed
Next talk due

Attendees

Name	Signature

Use the Print handout button to print this record. General guidance only, not legal advice.

Free H&S guidance

Hot Works
free guidance

Get plain-English guidance on your rights and your employer's legal duties.

HSE Infoline

0300 003 1747

hse.gov.uk

ACAS

0300 123 1100

acas.org.uk

Citizens Advice

0800 144 8848

citizensadvice.org.uk

UK Work Rights

Hot Works

ukworkrights.co.uk/toolbox-hotworks.html

Hot Works:The Fire That Starts After You Leave