Hot Work Risk Assessment: 5 Steps for UK Contractors

Every hot work job — welding, cutting, angle grinding, brazing, torch work — should be covered by a risk assessment before work begins. Not as a box-ticking exercise, but as the foundation that makes your hot work permit meaningful. Without an assessment, the permit has no risk basis. Without the permit, the assessment has no job-level implementation check.

This guide walks through a five-step hot work risk assessment, what the legal requirements are, and what distinguishes an assessment that protects workers from one that just protects the company from the first sentence of an investigation report.

This guide is based on the Regulatory Reform (Fire Safety) Order 2005 (SI 2005/1541), which applies in England and Wales, and the Dangerous Substances and Explosive Atmospheres Regulations 2002 (SI 2002/2776), which apply in Great Britain. Scotland and Northern Ireland have their own fire safety legislation, and Northern Ireland has its own version of DSEAR. It is for general information and does not constitute legal advice.

What the law requires

In England and Wales, under Article 9 of the Regulatory Reform (Fire Safety) Order 2005 (SI 2005/1541), the "responsible person" must conduct "a suitable and sufficient assessment of the risks to which relevant persons are exposed" to identify necessary fire precautions. Hot work introduces ignition sources, so the fire risk assessment needs to cover it: article 9(3) requires the assessment to be reviewed where "there has been a significant change in the matters to which it relates", and where a dangerous substance is involved, article 9(8) says no new work activity may commence unless "the risk assessment has been made" and the measures required by the Order have been implemented.

Article 12 of the same Order requires the responsible person to ensure that "risk to relevant persons related to the presence of [a dangerous substance] is either eliminated or reduced so far as is reasonably practicable." Where a dangerous substance (as defined in article 2 of the Order) is present in or on the premises where hot work is planned, that requirement applies directly to the hot work.

Where a dangerous substance is or is liable to be present at the workplace, the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) impose a parallel duty: a suitable and sufficient DSEAR risk assessment is required, and ignition sources must be controlled as part of the protective measures. Hot work introduces ignition sources by design, so it needs particular control in DSEAR-relevant environments.

The practical outcome: hot work needs a risk assessment that covers the specific job — not just a permit. On construction sites, HSE's HSG168 (paragraph 122) says the assessment should involve a visit to the hot work area, and to "Make a record of the site assessment and controls needed". Whether the law itself requires a written record depends on where you are and how many people you employ (see Step 4).

The 5 steps of a hot work risk assessment

Step 1: Identify the hazards

What could start a fire or explosion, and what would it affect?

For hot work, the immediate ignition hazards are straightforward: sparks, heat and flame. The less obvious hazards are the ignition sources the work creates that don't stay where the work is happening:

Sparks from angle grinding can travel well beyond the immediate work area
Heat conducted through steel structures can ignite materials in adjacent spaces or rooms (HSG168 paragraph 59)

The assessment should also identify the fire load in and around the work area: combustible materials, flammable liquids, stored gases, building finishes, insulation, and void spaces that could carry fire.

Step 2: Decide who might be harmed and how

Hot work risk isn't confined to the person doing the welding. An assessment should consider:

Workers directly involved in the hot work — exposure to sparks, fumes, UV radiation, and proximity to fire
Workers in adjacent areas who may be in the path of sparks or in spaces where heat or smoke can travel
Maintenance and facilities staff who may access the building during or after the hot work without knowing it has happened
Members of the public if the work is near a public-accessible area of a building or site
Occupants of adjacent premises — particularly relevant in occupied commercial or residential buildings

The fire safety case for hot work is stronger when the assessment maps out who is actually at risk, not just who is standing next to the welder.

Step 3: Evaluate the risks and apply controls

For each hazard identified, the assessment considers: what controls are needed to either eliminate the hazard or reduce the risk to an acceptable level?

The established control hierarchy for hot work fire risk:

First choice: can the ignition source be eliminated? Can the work be done cold — mechanical cutting, crimping, cold joining, hydraulic tools? If yes, the hot work fire risk is eliminated at source. A cold work permit may be used in its place where your permit system requires one.

Where hot work cannot be avoided:

Remove loose combustible materials from in and around the work area, from breaches in walls, floors and ceilings, from the area beneath the work, and from the other side of any wall or partition being worked on (HSG168 paragraph 122)
Where combustible material cannot be removed, protect it, and any openings, with non-combustible board (HSG168 paragraph 122)
If part of the fire alarm or detection system has to be isolated to avoid false alarms, notify the alarm monitoring company, and follow HSG168 paragraph 122: "implement robust procedures to ensure it is reactivated when work is completed or stops at the end of the day or for a break"
Confirm gas/atmospheric conditions: if DSEAR is engaged, test the atmosphere with a calibrated combustible gas detector before work starts (HSG168 paragraph 122 includes "Provide and use combustible gas detectors and/or thermal imaging cameras as appropriate")
Designate and brief a fire watch person — someone whose only job during the hot work is fire vigilance
Provide at least two suitable fire extinguishers within reach of the hot work and any fire watch location (HSG168 paragraph 122)

The hot work permit is the document that records these controls have been put in place before each individual job.

Step 4: Record findings

Whether the law requires a written record depends on where you are and how many people you employ. In England and Wales, article 9(6) of the Fire Safety Order (as amended by the Building Safety Act 2022, in force from 1 October 2023) requires the responsible person to make a record of the fire risk assessment, whatever the number of employees. In Scotland and Northern Ireland, the duty-holder must record specified information about the fire safety assessment where they employ five or more employees, where a licence or registration is required for the premises, or where an alterations notice requires it (Fire Safety (Scotland) Regulations 2006 regulation 8; Fire Safety Regulations (Northern Ireland) 2010 regulation 8). Regulation 3(6) of the Management of Health and Safety at Work Regulations 1999 (Great Britain; Northern Ireland has equivalent 2000 Regulations) also requires employers with five or more employees to record the significant findings of their risk assessment. On construction sites, HSG168 paragraph 122 says to "Make a record of the site assessment and controls needed" for hot work. Whatever the legal minimum, the record is also the mechanism that makes the assessment usable at the permit stage.

An effective hot work risk assessment record should include:

The work location and description
Fire hazards identified and their location in relation to the work
Persons at risk (by role, not just by name)
Controls specified for each hazard
The combustible clearance applied (what was removed, from where, and what was protected instead) and why
Atmospheric testing requirements (if DSEAR-relevant)
Fire watch duration requirement after the work finishes
Date of assessment and assessor's name and competence

A generic "hot work risk assessment" that doesn't reference the specific work location and conditions is unlikely to satisfy "suitable and sufficient."

Step 5: Review and update

The risk assessment should be reviewed:

Before each new hot work job in a different location or involving different conditions from where the assessment was originally conducted
When site conditions change significantly (new materials stored, new occupants, changes to fire detection systems)
After any hot work incident or near-miss — even if the work was completed without a fire, a near-miss is evidence that the controls were not sufficient

The same assessment cannot be reused indefinitely across multiple jobs. A statement in the assessment that it "applies to all hot work on this site" is a flag that it was produced for form-filling purposes.

What makes a hot work risk assessment "suitable and sufficient"

The "suitable and sufficient" standard comes from article 9 of the RRO 2005 and regulation 3 of the Management of Health and Safety at Work Regulations 1999 (and, where dangerous substances are present, regulation 5 of DSEAR). It is tested after an incident — by the HSE, by insurers, and in proceedings.

A suitable and sufficient assessment:

Is specific to the actual work and actual location (not templated across all sites)
Identifies the actual fire load in and around the work area (not just generic "combustible materials")
Records control measures that are proportionate to the identified hazards
Is conducted by someone with enough knowledge of fire behaviour and the work processes involved to identify hazards they cannot see — such as void spaces, adjacent materials, and structural heat transfer
Is reviewed before each job where conditions differ from the previous assessment

An assessment that lists controls without specifying who ensures each control is in place before work starts is incomplete — the permit is the mechanism for that verification.

Fire watch: the control that continues after the work stops

Plan for a fire watch wherever combustibles could have been exposed to sparks or heat. HSG168 accepts a different procedure only "where a suitable and sufficient risk assessment clearly demonstrates that the risk of a fire from hot works is minimal" (paragraph 125). For the watch itself:

The fire watch person should remain in the work area for a minimum period after hot work ceases (on construction sites HSE's HSG168 asks for a continuous fire watch for at least an hour, plus at least one more check two hours after hot work ends; some sites and insurers set their own fire-watch periods, which may be longer, so check your contract and policy)
The person assigned to fire watch should have no other duties during that period
The watch covers the full area that sparks or heat could have reached — not just the immediate work face

The post-work watch exists because, as HSG168 paragraph 123 puts it, "Some combustible/higher-risk materials can smoulder for a significant period of time after work has been completed and before they ignite." For construction, HSG168, Fire safety in construction (third edition, 2022, paragraph 122) says "There should be a continuous fire watch of the hot work area for at least an hour after the end of hot work, followed by at least one more check two hours after the end of hot work." See our fire watch requirements guide for the HSE baselines and when longer periods apply.

Practical checklist before hot work starts

Before any hot work begins, the following should be confirmed — and the hot work permit is the document that records this confirmation:

Hot work risk assessment completed and specific to this location
Loose combustibles removed from the work area, from breaches in walls, floors and ceilings, from the area beneath and from the far side of any wall being worked on — or protected with non-combustible board
Atmospheric check completed where DSEAR is engaged
Fire detection addressed (any isolated part has a procedure to reactivate it, or confirmed not affected)
At least two suitable fire extinguishers within reach of the hot work and the fire watch location
Fire watch person designated, briefed, and free from other duties
Adjacent spaces and building occupants notified
Method for stopping work and summoning emergency services confirmed

Key references

Regulatory Reform (Fire Safety) Order 2005 (SI 2005/1541) — Articles 9 and 12 on fire risk assessment and dangerous substance duty, current text as amended (England and Wales)
Dangerous Substances and Explosive Atmospheres Regulations 2002 (SI 2002/2776) — DSEAR duties where dangerous substances are or may be present (Great Britain)
HSE DSEAR guidance — practical information on classifying areas where explosive atmospheres may occur and avoiding ignition sources
HSG168: Fire safety in construction — HSE, third edition 2022; paragraph 122 on precautions before, during and after hot work (combustibles, extinguishers, fire watch) and paragraph 123 on delayed ignition

Disclaimer

This guide is for general information only. Legal duties depend on the specific work, location, and site conditions involved. Always consult a competent fire safety or H&S professional and the primary legislation for your circumstances.