A contractor arrives to clean a tank. The entry permit is printed, a gas monitor is on the bench and the site team expects the fire service to deal with any emergency. That is not a complete confined-space system. The employer or dutyholder must first decide whether entry can be avoided, assess the particular space and task, put effective precautions in sequence and make adequate rescue arrangements before anyone goes in.
Decide whether it is legally a confined space
A confined space is not defined simply by size, darkness or a narrow entrance. It is a place that is enclosed or largely enclosed and where a reasonably foreseeable specified risk exists: fire, explosion, loss of consciousness, asphyxiation or drowning. Tanks, silos, sewers and vessels are obvious examples, but pits, vats, ductwork, chambers and poorly ventilated rooms can also qualify.
The classification can change with the work. A chamber that is safe while empty may become a confined space when cleaning chemicals, welding fumes, nitrogen, hot work or flowing material are introduced. Conversely, an awkward cupboard is not automatically a confined space if none of the specified risks is reasonably foreseeable. Record the reasoning rather than labelling every enclosed place in the same way.
The general risk assessment under the Management Regulations comes first. If it identifies a risk of serious injury from confined-space work, the Confined Spaces Regulations 1997 apply. The assessment should address the task, environment, materials and tools, the people doing the work and emergency rescue arrangements.
HSE: introduction to working in confined spaces ↗ · HSE: confined-space legislation ↗
Avoid entry before designing the permit
Regulation 4 requires work in a confined space to be avoided so far as is reasonably practicable. That is a design and planning question, not a box at the bottom of an entry form. Consider remote cameras, external sampling, fixed cleaning heads, long-reach tools, purging connections, redesigned access or removing a component to a safer work area.
If entry is genuinely necessary, record why the outside-work option is not reasonably practicable. A production deadline, a familiar contractor or the existence of a permit system does not answer that question. North East manufacturers, utilities, farms and engineering businesses should also challenge repeat entries: recurring tank cleaning or inspection may justify a permanent engineering change.
Where entry cannot be avoided, regulation 4 requires a safe system of work. It should be written, site- and task-specific, and implemented in the correct sequence. A permit may authorise the entry, but it cannot create the controls that the assessment failed to specify.
Build the safe system around the actual space and task
Start with positive isolation. Prevent machinery from moving and stop gases, liquids, steam, electricity or free-flowing solids entering the space. Lock, tag and prove isolations; closing a control valve or pressing a stop button may not be enough. Remove or control residues, and check whether external work or adjacent plant can change conditions inside.
Decide what atmospheric testing is required, where and when. A competent person should use a suitable, correctly calibrated detector for the foreseeable contaminants and oxygen range. Test remote pockets and different levels where gases may stratify. If conditions could change, continuous monitoring may be needed. A normal reading at the opening before the shift is not proof that the atmosphere will remain safe.
Then specify ventilation, access and egress, lighting, communications, supervision, work equipment, PPE or RPE, and limits on time inside. Workers need competence for their particular roles—not merely a generic certificate. Consider fitness, claustrophobia, heat, restricted openings and the ability to use breathing apparatus. Reasonable adjustments must not create an uncontrolled rescue problem.
HSE: confined spaces—brief guide INDG258 ↗ · Related guide: contractor management checklist →
Use the permit as a live control, not a certificate
A permit-to-work is appropriate where formal authorisation and communication are needed. It should identify the space, task, people, validity period, isolations, test results, ventilation, equipment, attendant, communications, rescue arrangements and conditions that stop the job. The issuer and receiver should understand their responsibilities and the handback process.
Do not pre-sign, copy yesterday’s readings or leave a permit open when the team, weather, process or connected plant changes. Suspend the permit if an alarm activates, ventilation fails, communications are lost, the task changes or the authorised period expires. Reassessment comes before re-entry.
Contractors must be included in the same system. The client should provide relevant plant, process, residue, isolation and emergency information; the contractor should provide task methods and competence evidence. Both sides should agree who controls the space and who can stop, suspend and close the permit.
Test the system before authorising the work.
HR + SAFETY can review the space, task, isolations, monitoring and contractor interface, then identify where specialist confined-space or rescue input is needed.
Discuss a confined-space assessmentPlan rescue before entry—not after an alarm
Regulation 5 requires suitable and sufficient emergency arrangements before a person enters or works in a confined space. Calling 999 is part of escalation, not the rescue plan. HSE is explicit that it is not enough to rely on the emergency services. The plan must reflect the likely emergency, access, atmosphere, casualty condition and time needed to recover them.
Decide how an alarm will be raised, who remains outside, who leads the response and whether non-entry recovery is possible. Provide suitable rescue and resuscitation equipment, protected rescuers, first-aid arrangements and practiced drills. A tripod and harness are useful only where the casualty can actually be recovered through the opening without snagging or further injury, and where trained people can operate the equipment.
Unplanned rescue regularly creates additional casualties. Nobody should enter to help unless the plan authorises it and they have the competence, protection and equipment required. Cover nights, weekends and shutdowns, not just the day shift when the usual rescue team is present.
HSE ACOP L101: safe work in confined spaces ↗ · Related guide: first-aid needs assessment →
Connect fire, explosion and vulnerable-person controls
Where flammable vapours, combustible dust, oxygen enrichment or hot work are foreseeable, assess ignition and explosion risks under DSEAR as well as the confined-space rules. Use suitable equipment and prevent oxygen from being used to improve stale air. If the work introduces or materially changes a fire or explosion hazard, review and update the statutory fire risk assessment.
Where the existing fire risk assessment cannot adequately address the process, complete a linked task-specific assessment—such as DSEAR or hot-work assessment—and incorporate its findings into the main FRA, emergency arrangements, permit controls, training and evacuation planning. Neither the permit nor a contractor’s RAMS substitutes for the statutory assessment.
Give additional attention to people whose health, mobility, body size, communication needs or equipment fit may affect entry or rescue. In complex process sites, public premises or workplaces where a failure could expose people beyond the entry team, strengthen isolation, alarm, exclusion and escalation arrangements to reflect the consequence—not just the likelihood.
Confined space risk assessment checklist
Legal requirements and official guidance were checked on 30 September 2026. The Confined Spaces Regulations 1997 remain in force. The sequence is unchanged: avoid entry where reasonably practicable; if entry is unavoidable, use a safe system of work; and put adequate emergency arrangements in place before work starts.
- Confirm that the place is enclosed or largely enclosed and identify each foreseeable specified risk.
- Assess the task, space, residues, connected plant, materials, tools and people involved.
- Record why entry cannot reasonably be avoided and consider remote methods first.
- Define, lock and prove mechanical, electrical and process isolations.
- Specify atmosphere tests, detector capability, calibration and continuous monitoring where needed.
- Set ventilation, access, communication, supervision, equipment and time limits.
- Confirm role-specific competence and individual suitability for the work and rescue arrangements.
- Issue a task-specific permit where formal authorisation is necessary.
- Set clear stop-work, suspension, re-test and handback conditions.
- Prepare, equip and practise a rescue plan that does not depend only on emergency services.
- Coordinate employees, contractors, attendants, permit issuers and rescuers.
- Review the assessment after change, alarm, failed control, near miss or learning from a drill.
The permit is the final authorisation point, not the beginning of the assessment. A defensible confined-space system first challenges the need to enter, then proves isolations and atmosphere controls, manages the live job and prepares rescuers for the emergency that could actually happen.
This guide provides general information for UK employers. It is not legal advice and should not replace advice based on the facts of a specific matter.