Hot Work Risk Assessment: The 5 Steps UK Contractors Follow

Every hot work job — welding, cutting, angle grinding, brazing, torch work — requires 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 the five steps UK contractors follow for a 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) and the Dangerous Substances and Explosive Atmospheres Regulations 2002 (SI 2002/2776). It is for general information and does not constitute legal advice.

What the law requires

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. For any work that introduces ignition sources — which is precisely what hot work does — this obligation is activated.

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 flammable materials or explosive atmospheres are possible in the hot work area, that reduction requirement is directly engaged.

For sites where flammable substances are present, 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 is the most common way ignition sources are introduced into DSEAR-relevant environments.

The practical outcome: every hot work job on a UK site with any fire or explosion risk needs a documented risk assessment — not just a permit.

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 hazards are straightforward: sparks, heat, flame, and the UV output from welding arcs. 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 up to 10 metres
Heat conducted through steel structures can ignite materials in adjacent spaces or rooms
Welding smoke can contaminate flammable vapour detectors, giving false-clear readings
Radiated heat from sustained welding can ignite materials several metres from the work face

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 is used in its place.

Where hot work cannot be avoided:

Remove combustible materials from the work area to the minimum safe clearance distance (commonly 10 metres, but verified against the specific work type and materials involved)
Where materials cannot be removed, protect them with welding blankets, fire-resistant barriers, or fire-retardant coverings
Isolate or deactivate fire detection systems that would give false alarms during the work — with the monitoring company notified and a compensatory arrangement in place
Confirm gas/atmospheric conditions: if DSEAR is engaged, atmospheric testing with a calibrated detector is required before work starts
Designate and brief a fire watch person — someone whose only job during the hot work is fire vigilance
Have appropriate extinguishing equipment immediately available (correct type and rating for the fire load)

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

Step 4: Record findings

Recording is a legal obligation where the employer has five or more employees (under the Management of Health and Safety at Work Regulations 1999 regulation 3(6)), but it's 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 clearance distance applied and why (if different from the standard 10m)
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 both the RRO 2005 and the Health and Safety at Work etc. Act 1974. 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 most commonly missed control

HSE investigation reports consistently identify the post-hot-work fire watch as the most frequently absent control when hot work fires occur. A fire watch is not optional where combustibles could have been exposed to sparks or heat:

The fire watch person should remain in the work area for a minimum period after hot work ceases (60 minutes is common UK site practice and a frequent insurer minimum; some sites and insurers require longer)
The person assigned to fire watch must 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 60-minute fire watch period reflects the documented behaviour of smouldering materials that ignite fully after hot work has finished and the team has left; it is widely adopted as a site practice minimum and common in insurer requirements.

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
Combustibles removed or protected within required clearance distance
Atmospheric check completed where DSEAR is engaged
Fire detection systems addressed (isolated with compensatory arrangements, or confirmed not affected)
Fire extinguisher of correct type available within 5m
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
Dangerous Substances and Explosive Atmospheres Regulations 2002 (SI 2002/2776) — DSEAR duties for sites with flammable substances
HSE DSEAR guidance — practical information on zone classification and ignition source control

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.