A permit to work is a formal, recorded process for controlling work that has been identified as potentially hazardous, such as hot work, confined space entry or work on isolated plant. It sets out who may do the job, where, when, and the precautions that must be in place. HSE's guidance (HSG250) is clear that a permit supports a safe system of work and a risk assessment; it never replaces them.
What is a permit to work?
HSE's Guidance on permit-to-work systems (HSG250) defines a permit-to-work system as "a formal recorded process used to control work which is identified as potentially hazardous". It is also a means of communication between site management, supervisors and the people doing the work.
The permit itself is the paper or electronic form. It authorises named people to carry out specific work at a specific location for a set time, and records the main precautions needed to do that job safely.
HSG250 lists the essential features of a permit system:
- clear identification of who may authorise particular jobs, any limits to their authority, and who specifies the precautions;
- training and instruction in the issue, use and closure of permits;
- monitoring and auditing to check the system works as intended;
- clear identification of the types of work considered hazardous;
- standardised identification of tasks, risk assessments, permitted duration, and any simultaneous activity and its controls.
HSG250 puts it plainly: a permit "is not simply permission to carry out a dangerous job", and "the issue of a permit does not, by itself, make a job safe". The safety comes from the people who plan, supervise and carry out the work.
HSG250 was written for the petroleum, chemical and allied industries, but construction guidance points back to it. HSE's fire guidance for construction, for example, refers readers to HSG250 for more detail on permit systems.
When do you need a permit to work?
HSG250 says permits should be considered whenever work may adversely affect the safety of people, plant or the environment. It names four situations where they are most appropriate: non-production work (maintenance, repair, construction, dismantling, modification, cleaning), non-routine operations, jobs where two or more groups must coordinate, and jobs where work and responsibility transfer from one group to another.
It also lists types of job where permits or certificates should be considered, including:
- work where heat is used or generated, such as welding, flame cutting or grinding, and work that may produce sparks;
- breaking containment of a flammable, toxic or other dangerous substance, or a pressure system;
- work on high-voltage equipment, or other electrical work that may give rise to danger;
- entry into and work in tanks and other confined spaces;
- work at height;
- pressure testing, and work affecting evacuation, escape or rescue systems.
Do not put everything on a permit. HSG250 warns that permit systems "should not be applied to all activities, as experience has shown that their overall effectiveness may be weakened". General visitors and routine work in non-hazardous areas do not normally need one.
Which permits are common on UK sites?
The law rarely says "you must use a permit". It sets duties, such as a safe system of work or proper planning, and a permit is how most sites show they have met them for higher-risk tasks. This table sets out the usual permit types and the law or guidance behind each.
| Permit | Typical hazards | Key controls | Law and guidance |
|---|---|---|---|
| Hot work | Fire from welding, cutting, grinding, torch-on roofing | Remove or protect combustibles, at least two extinguishers, fire watch during and for at least an hour after, a further check at two hours | HSG168 Fire safety in construction, paras 118–132 |
| Confined space entry | Loss of consciousness, asphyxiation, fire, explosion, drowning | Avoid entry if possible; gas testing, ventilation, isolation, time limits, a rescue plan in place before entry | Confined Spaces Regulations 1997, regs 4–5; ACOP L101 |
| Electrical isolation | Shock and burns from equipment that is, or becomes, live | Isolate, lock off with the worker holding the keys, prove dead with suitable test equipment | Electricity at Work Regulations 1989, regs 12–14; HSG85 |
| Excavation (permit to dig) | Striking buried services, collapse, falls into the excavation | Service plans, locate and mark services, safe digging, supports or battering, inspection at the start of each shift | CDM 2015 reg 22; HSG47 |
| Work at height | Falls of people and objects | Avoid work at height where reasonably practicable; otherwise take suitable measures to prevent falls | Work at Height Regulations 2005, reg 6 |
| Lifting operations | Dropped or swinging loads, overturning, contact with structures | Planned by a competent person, appropriately supervised and carried out safely | LOLER 1998, reg 8 |
Two of these deserve a closer look. For confined spaces, regulation 4 says no one should enter to work unless there is no reasonably practicable alternative, and regulation 5 requires rescue arrangements before anyone goes in. ACOP L101 says a permit is "usually required where there is a reasonably foreseeable risk of serious injury" and is "an extension of the safe system to work, not a replacement for it". For electrical work, HSE says conductors should be proven dead before work starts, with a lock on each isolation device and the worker holding the keys. Live work is allowed only in the narrow cases set out in regulation 14.
Who does what on a permit?
Sites use different job titles, so HSG250 sets out common role names.
| Role | What they do | Other names you may hear |
|---|---|---|
| Issuing authority | Issues the permit and confirms isolations and precautions are in place | Permit issuer, permit coordinator, responsible person |
| Permit authoriser | A second check before issue, for high-hazard work | Approver |
| Performing authority | Accepts the permit for the work team and makes sure everyone understands it | Acceptor, person in charge of the work |
| Area authority | Controls the location where the work happens | Area operator, system operator |
| Isolating authority | Makes and removes isolations | Authorised person (electrical, mechanical, process) |
| Site checker | Carries out checks listed on the permit, such as gas tests | Gas tester |
HSG250 adds two rules worth writing into any procedure: nobody should issue a permit to themselves, and high-hazard permits should be seen by a second person before issue.
How does a permit move from request to close?
Every site's form differs, but the stages are broadly the same. They follow the essential elements of a permit form in HSG250 Figure 1.
- Request. The contractor describes the job, location, plant, team and timing, with a reference to the risk assessment and method statement.
- Assess. The issuer visits the location, identifies hazards (including those left over from other work) and decides on precautions, PPE and any certificates needed, such as an isolation or gas-test certificate.
- Isolate and prepare. Isolations are made and recorded by the isolating authority, who signs that they are in place.
- Issue. The issuer signs, with date and time, and states how long the permit is valid.
- Accept. The performing authority signs to confirm they understand the work, hazards and precautions, and that they have briefed the team.
- Display and work. Copies are displayed at or near the job and at the control point. The issuer checks the work at least at the start and at completion.
- Suspend, restart or extend. If work stops, the permit is suspended and the plant's condition is recorded. Work restarts only once the issuer has confirmed it is safe. A shift handover or extension is signed off with a new expiry time.
- Hand back. The performing authority confirms the work is complete, and the issuer confirms the plant is safe and ready for testing.
- Close. The permit is cancelled once the plant has been tested and returned to service, and the records are kept. HSG250 suggests keeping them on site for at least 30 days.
One point catches people out: a suspended permit is still live until it is cancelled, so isolations made under it may still be in place.
Where do permit systems fail?
HSG250 draws on incident investigations, including the Piper Alpha disaster in 1988. HSE's technical measures guidance for major-hazard sites lists failures such as the wrong type of permit, wrong information about the job, permit terms not followed (for example, plant not isolated), communication failures, and unauthorised staff carrying out permit functions. The patterns that recur:
- No permit for the actual job. In one HSG250 case study, permits were issued for removing a lid and for blanking an inlet, but not for raking out the vessel. Five people died.
- Missing isolations. An issuer who did not know the process controls listed the mechanical and electrical isolations but missed the process ones.
- No cross-referencing. On Piper Alpha, work under one permit affected work under another with nothing to link them, and people relied on memory.
- Permits not displayed. The Piper Alpha inquiry found permits were often kept in pockets rather than shown at the job site.
- Poor handover. The night-shift handover on Piper Alpha did not pass on that a safety valve had been removed and not replaced.
- No sign-off. A fitter was scalded when a colleague handed back a shared permit before both parts of the job were finished.
- Too many permits for one issuer. HSG250 warns that supervision is diluted when one person controls many permits, especially during shutdowns.
On construction sites, look out for blanket hot-work permits. HSG168 says permits "should not give blanket authorisations to carry out hot works anywhere on site at any time".
Paper or electronic permits?
Either can work. HSG250 says that before using electronic permits you should make sure that:
- electronic signatures or similar controls prevent unauthorised issue or acceptance;
- permits cannot be issued remotely without a site visit;
- permits already issued cannot be altered without everyone concerned being told;
- paper copies can be produced for display at the job site;
- issuers assess each job rather than copying sections from other permits;
- there is a back-up if the software or power fails.
How Assured Contractors helps
Assured Contractors permits to work cover hot work, confined space, work at height, electrical isolation, excavation and lifting. Each permit follows the same lifecycle: request, assess, issue, suspend, restart, extend, hand back and close. It carries checklists, hazards and controls, and can be printed as a PDF for display. Once issued, a permit is locked against editing. Permits sit alongside jobs, which list the qualifications the work requires. Each step is recorded in the audit log. Contractors whose people work under the permits use Assured Contractors free.
Questions
Is a permit to work a legal requirement?
Usually not by name. The law requires safe systems of work, planning and precautions: for example, regulation 4 of the Confined Spaces Regulations 1997 and regulation 8 of LOLER. A permit is the recognised way of showing that control for higher-risk work. HSE's confined spaces code of practice (L101) says a permit is usually required where there is a reasonably foreseeable risk of serious injury.
Does a permit replace a risk assessment or method statement?
No. HSG250 treats the permit as part of the task risk assessment process and says the issue of a permit does not, by itself, make a job safe. The permit should reference the risk assessment and method statement and confirm their precautions are in place.
Who can issue a permit to work?
Only people the site has trained and authorised in writing. HSG250 says nobody should issue a permit to themselves, and high-hazard work should have a second person (a permit authoriser) review it before issue.
How long should a permit last?
Only as long as the defined job at that location, and no longer than the validity period written on it. If work runs into another shift, a formal handover or extension should be signed. HSE's construction fire guidance says hot-work permits should cover clearly defined work for a specified period, never the whole site at any time.
What is the difference between suspending and cancelling a permit?
A suspended permit stays live, and so may its isolations. Work restarts only when the issuer confirms it is safe. A cancelled permit is closed, so if the job starts again it is treated as new work with a new permit.
Sources
Checked 11 November 2026. Legislation links go to legislation.gov.uk; guidance links to the publisher's own pages.
- HSE, HSG250 Guidance on permit-to-work systems (2005)
- HSE, HSG168 Fire safety in construction (third edition, 2022)
- HSE, L101 Safe work in confined spaces, ACOP (third edition, 2014)
- Confined Spaces Regulations 1997 (legislation.gov.uk)
- Electricity at Work Regulations 1989 (legislation.gov.uk)
- HSE, HSG85 Electricity at work: safe working practices
- HSE, Electrical safety FAQs
- CDM 2015 regulation 22: Excavations (legislation.gov.uk)
- HSE, HSG47 Avoiding danger from underground services
- Work at Height Regulations 2005 regulation 6 (legislation.gov.uk)
- LOLER 1998 regulation 8 (legislation.gov.uk)
- HSE, Permit to work systems: technical measures (COMAH)
This guide is general information, not legal advice. Check the current legislation and guidance for your own site and work.