Contents
1. What a permit to work is 2. When a permit is required 3. Types of permits: full classification 4. Who issues and who signs 5. How a permit is raised, extended and closed 6. How long a permit stays valid 7. Work that needs no permit 8. Liability and enforcement 9. Permits by industry 10. Frequently asked questionsHot work, entry into a vessel, work on a live board, lifting over a running line — four different jobs, four different permits, four different sets of signatures. Pick the wrong form and the paperwork is worthless the moment something goes wrong. And to clear the most common confusion first: this is not the immigration paper. If you are after a visa-type work permit for foreign employment, you are on the wrong site — everything here is the industrial safety document.
1. What a permit to work is
A permit to work (PTW) is a written authorisation that names a specific job, in a specific place, for a specific window of time, and states the precautions that must be in place before it starts. It is a control document, not a form to file: it exists so that the person who understands the plant and the person who will do the work agree, in writing, on what has been isolated, tested and made safe.
Three parties meet on a permit. The issuing authority knows the installation and confirms it is safe to release. The performing authority accepts the conditions and is answerable for the crew. The area authority — where the operator uses one — confirms nothing else in the area conflicts with the work.
The permit answers five questions and refuses to be vague about any of them: what exactly is being done, where the boundary of that work lies, which energy sources have been isolated and proved dead, what has been measured, and when the authorisation runs out.
2. When a permit is required
Practice differs by country and by operator, but the trigger is consistent: a permit is required when the work introduces a hazard that the normal controls of the area do not cover.
| Work | Why a permit | Typical reference |
|---|---|---|
| Hot work | Ignition source in an area that may hold flammable vapour | NFPA 51B; operator hot-work standard |
| Confined space entry | Atmosphere may be oxygen-deficient, toxic or flammable; escape is restricted | OSHA 1910.146; NOM-033-STPS (Mexico) |
| Electrical work | Stored or live energy; isolation and proving needed | NFPA 70E; IEC 61936 practice |
| Work at height | Fall risk; access equipment and rescue plan needed | Operator standard; national height rules |
| Excavation | Buried services, collapse, atmosphere at depth | Underground services survey + permit |
| Lifting over live plant | Dropped load onto operating equipment | Lift plan + permit, LOLER-style practice |
Where two of these overlap — welding inside a vessel is the classic case — the operator raises both permits and each references the other. A single combined form is where control quietly disappears: one signature ends up covering two hazards that were assessed by different people.
3. Types of permits: full classification
Names vary between operators; the underlying set does not.
| Permit | Scope | Defining control |
|---|---|---|
| Hot work | Welding, cutting, grinding, open flame | Gas test before and during; fire watch |
| Cold work | Mechanical work with no ignition source | Isolation and physical boundary |
| Confined space entry | Vessels, tanks, pits, sewers | Continuous atmosphere monitoring; attendant; rescue plan |
| Electrical isolation | Switching, racking, work on de-energised gear | Lock-out, tag-out, prove dead |
| Excavation | Digging, trenching, ground breaking | Services survey; shoring |
| Radiography | Industrial NDT with radiation sources | Exclusion zone; dose control |
| Diving / overside | Work below the waterline or over the side | Simultaneous-operations control |
4. Who issues and who signs
Roles are what auditors read first, because a permit signed by the wrong person is not a permit at all.
- Issuing authority — competent for the installation; authorises release and states the isolations.
- Performing authority — leads the crew; accepts conditions and hands the area back.
- Area authority — controls the operating area; confirms nothing conflicts.
- Gas tester — separately certified; the readings carry their name, not the issuer's.
- Attendant / fire watch — stays for the duration and has the authority to stop the work.
One rule survives every jurisdiction: the person who issues a permit does not perform the work under it. Where those two roles collapse into one signature, the check is gone.
5. How a permit is raised, extended and closed
- Job scoped and risk-assessed; hazards identified.
- Permit type chosen; conflicting work checked across the area.
- Isolations applied, locked and tagged; energy proved dead.
- Atmosphere tested; readings written with time and instrument serial.
- Precautions confirmed on site by the issuing authority.
- Permit signed by issuer and acceptor; copy displayed at the worksite.
- Work proceeds within the stated boundary only.
- Extension — only after re-testing and re-signing, never as a formality.
- Handback: area cleared, isolations removed, permit closed and retained.
Closure matters as much as issue. An unclosed permit means isolations may still be live in the field while the control room believes the job is finished.
6. How long a permit stays valid
| Permit | Typical validity | Extension |
|---|---|---|
| Hot work | One shift; often shorter | Re-test the atmosphere, then re-sign |
| Confined space entry | One shift, continuous monitoring | New entry after any break in attendance |
| Cold work | Up to several days on some sites | Daily re-validation by the area authority |
| Electrical isolation | Duration of the isolation | Tied to the lock-out register |
The pattern is the same everywhere: the higher the hazard, the shorter the window, and the more often the conditions must be re-proved rather than re-assumed.
7. Work that needs no permit
Routine operation, visual inspection from a safe distance, work in a workshop away from process plant, and tasks fully covered by a standing procedure normally sit outside the permit system.
8. Liability and enforcement
Enforcement is national and differs sharply. What does not differ is what an inspector looks for after an incident: whether a permit existed, whether the named people were competent, whether the readings were real, and whether the closure was recorded. Missing or retrospectively completed paperwork moves a case from an accident towards a failure of control.
| What the inspector finds | How it reads | Who usually carries it |
|---|---|---|
| No permit for work that required one | Failure of the control system, not a paperwork slip | Employer and the responsible manager |
| Permit signed by someone not competent for the role | The authorisation is treated as absent | Whoever appointed them |
| Gas readings written but not taken | Falsified record — the heaviest finding of the set | The named tester personally |
| Permit never closed, isolations left in the field | Live hazard handed to the next shift | Issuing and area authority |
| Form completed after the incident | Moves the case from accident towards concealment | Everyone who signed it |
Naming the country's own regulator is a job for the country pages, not for a general guide: the labels differ, but the five findings above appear in incident reports everywhere.
9. Permits by industry
Oil and gas. The most developed systems; hot work and entry dominate, and simultaneous operations control is the hard part.
Power generation and grid. Electrical isolation is the centre of gravity; switching programmes tie into the permit.
Construction. Height, excavation and lifting; the challenge is contractor interface, not the form.
Chemicals and metals. Atmosphere and thermal hazards; entry permits carry the heaviest testing regime.
10. Frequently asked questions
Is a “permit to work” the same as a work permit for a foreign employee?
No, and the two are constantly confused in search. A permit to work is a safety authorisation for a hazardous job. A work permit is an immigration document. This site is about the first one only.
Can one permit cover several crews?
Only if every crew is named and each performing authority signs. In practice separate permits are cleaner and survive audit better.
Does a digital permit have the same standing as paper?
In most jurisdictions yes, provided the record is attributable, time-stamped and cannot be altered after signature.
What is the difference between a permit to work and a method statement?
The method statement describes how the job will be done; the permit authorises it to start at a specific time and place, once the stated precautions are proved. One describes, the other permits — a job on live plant usually needs both.
Who may cancel a permit?
The issuing authority, the area authority, and anyone holding stop-work authority — including the attendant or fire watch.