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Permit-to-work deep dive
Hot work, confined space, working at height, energy isolation — the control hierarchy, the audit trail, and the handover pattern that keeps a PTW system honest.
18 min read · updated 2026-04-05 · 3 sections
Why PTW exists
A permit-to-work system exists to force a pause before a high-risk task begins. Its primary purpose is not documentation — it is the conversation between the requestor, the authorising person, and the affected operations. The document is the evidence of that conversation.
The six permit classes
| Class | Trigger | Key controls |
|---|---|---|
| Hot work | Spark / flame / temp > 400°C | Fire watch, gas test, combustibles cleared |
| Confined space | Entry into tank / vessel / pit | Atmospheric monitoring, rescue plan, entry log |
| Working at height | Above 1.8m with fall risk | Fall arrest, inspected harness, competent person |
| Energy isolation | Any stored / hazardous energy source | LOTO, try-out, isolation certificate |
| Excavation | Ground disturbance > 300mm | Utility search, shoring plan, access control |
| Critical lift | Tandem / non-standard load | Engineered plan, exclusion zone, competent signaller |
The PTW lifecycle
- Request — work description, location, planned window, hazards identified.
- Assess — JSA attached, controls listed, competencies verified.
- Authorise — authorising person signs, operations concurrence recorded.
- Issue — physical/digital permit posted at work site, copy to control room.
- Execute — monitoring on agreed frequency, hold points for gas tests etc.
- Close — permit surrendered, site inspected, isolation removed, records retained.