A Permit to Work (PTW) system is a formal, written control process used to manage high‑risk, non‑routine or hazardous activities. It provides documented authorisation for specific work to proceed, confirms that hazards have been identified and controlled, and ensures that all relevant parties understand the conditions under which work may be carried out.
Example of activities that require a Permit To Work include:
- Hot work (e.g. welding, cutting, grinding, brazing, use of blow lamps)
- Confined space entry (e.g. tanks, vessels, pits, silos, sewers, manholes)
- Electrical work (e.g. work on live systems, high‑voltage equipment, temporary supplies)
- Work at height (e.g. non‑routine roof access, MEWPs, fragile surfaces)
- Breaking containment or line breaking (e.g. opening pipes, ducts, pressurised systems)
- Isolation of energy sources (e.g. electrical, mechanical, hydraulic, pneumatic, thermal – LOTO)
- Maintenance, repair or modification of plant and machinery
- Excavation and groundworks (e.g. near underground services, deep or unsupported excavations)
- Hazardous substances work (e.g. bulk chemical handling, contaminated plant cleaning)
- Work in flammable, explosive or oxygen‑deficient atmospheres
- Use of explosives or high‑energy tools (where applicable)
- Simultaneous operations (SIMOPS) where multiple activities interact
- Contractor work in operational or live environments
- Non‑routine lifting operations or complex lifts
- Any task where failure of controls could result in serious injury, fatality, major asset damage or environmental harm
A PTW system does not replace a Safe System of Work but instead, it aligns with and complements it. The SSOW defines how work should be done safely, while the PTW acts as a task‑specific control mechanism that confirms the SSOW is suitable and sufficient, current, and properly implemented for the particular activity, time, and location. PTWs introduce an additional layer of planning, communication, and verification where the consequences of failure are potentially severe.
An effective PTW system typically includes:
- Clear identification of the work scope, location, and duration
- Formal hazard identification and Safe Systems Of Work
- Verification of isolations, energy control, and environmental conditions
- Defined roles and responsibilities, including competent authorisation
- Communication and coordination with other activities or contractors
- A structured handover, suspension, and close‑out process
- Periodic monitoring and review to ensure controls remain effective
Failure to control relevant activities through a PTW system can result in:
- Uncontrolled exposure to high‑risk hazards (e.g. work at height, energy, confined spaces, fire)
- Poor communication and conflicting activities
- Breakdown of isolation and control measures
- Increased likelihood of serious injury, fatality, asset damage, or environmental harm
- Non‑compliance with legal and industry standards, leading to enforcement action
In summary, a PTW system is a critical risk management tool that strengthens Safe Systems Of Work by ensuring high‑risk activities are carefully planned, authorised, communicated, and controlled.
Written by Daniel Prosser, MSc CMIOSH L4DipFRA OSHCR
Health, Safety and Wellbeing Professional