Control of Work (CoW) is a formalized management system designed to govern operational activities that carry inherent risk. This structured approach ensures that any work, particularly non-routine tasks, is conducted with full awareness of potential hazards and with appropriate safety measures in place. CoW establishes a procedural framework for the systematic planning, authorization, execution, and review of tasks that could cause harm to personnel, damage equipment, or negatively impact the environment. It functions as a standardized methodology for maintaining safety and operational control across complex industrial environments. The system acts as a deliberate gateway, ensuring that only qualified personnel proceed under controlled conditions, thereby reducing the likelihood of accidents and maintaining regulatory compliance.
Defining the Scope of Control of Work
Control of Work is an overarching framework, not a single document, encompassing all management processes necessary to control non-routine or higher-risk operational activities. The system is designed for tasks outside of standardized, low-risk work, such as maintenance, modifications, construction, or project-based assignments. These activities often involve interaction with energy sources, working in confined spaces, performing hot work, or working at heights. CoW is used in industries where the consequences of an incident are severe, including oil and gas, chemical processing, heavy manufacturing, and utilities. The framework provides visibility into all concurrent work activities, preventing simultaneous operations (SIMOPS) from creating unforeseen hazards. By requiring formal authorization for high-risk tasks, the system ensures that multiple layers of defense are established before work commences.
The Fundamental Purpose of CoW
The core objective of implementing a Control of Work system is to proactively mitigate operational risk before work begins. CoW functions as a systematic barrier against accidents and injuries by ensuring that hazards are identified and controlled during the planning stage. This process is foundational to upholding regulatory compliance, as many safety bodies require formalized systems for managing high-hazard operations. The framework also standardizes work processes, making the execution of non-routine tasks predictable and repeatable. Ultimately, CoW establishes a documented procedure that confirms all necessary precautions are in place, making accountability clear for every step of the work process.
Permit to Work Systems: The Practical Engine
The Permit to Work (PtW) system is the most recognizable component of the Control of Work framework, serving as the formal authorization document for high-risk activities. A PtW is a procedure that outlines the specific scope, location, duration, and required precautions for a given task. It ensures that all necessary checks and sign-offs are completed by competent personnel before work can commence.
The PtW lifecycle begins with the work request, defining the task and identifying initial hazards. A comprehensive review and approval stage follows, where technical and safety experts confirm the adequacy of proposed controls. Once authorized, the permit is formally issued, signaling the start of the execution phase, during which the work is monitored for compliance.
The permit must be visibly displayed at the worksite, informing all personnel of the hazards and necessary procedures. If conditions change or a shift handover occurs, the permit must be suspended or formally renewed. Final closure requires documented confirmation that the work area is safe, the task is complete, and the equipment is ready for return to normal operation.
Integrated Safety Tools within CoW
Hazard Identification and Risk Assessment
All work conducted under the CoW system must be preceded by a formal analytical process to identify and evaluate potential risks. This often takes the form of a Job Safety Analysis (JSA) or a Hazard Identification and Risk Assessment (HIRA), which systematically breaks down the task into steps. For each step, potential hazards are identified, the associated risk is evaluated, and control measures are determined.
These necessary controls are then integrated directly into the Permit to Work document. Controls are applied using the hierarchy of controls, focusing first on elimination and substitution, then on engineering controls, before relying on administrative controls and personal protective equipment (PPE).
Isolation Management and LOTO
Isolation management is a technical element of Control of Work designed to prevent the unexpected release of energy or materials during servicing or maintenance. This process ensures equipment is safely de-energized and secured from all hazardous energy sources, including electrical, mechanical, hydraulic, pneumatic, and thermal energy. Lockout/Tagout (LOTO) procedures are the administrative means of achieving this physical isolation.
LOTO involves applying a physical lock to an energy-isolating device, such as a breaker or valve, to prevent its operation. A corresponding tag warns against re-energization and identifies the person who applied the lock. The procedure requires a “try-out” step to verify the isolation is effective and all stored energy has been dissipated. The status of all isolations must be documented and referenced on the PtW.
Operational Handover Procedures
Formal operational handover procedures manage the transfer of responsibility for a worksite or equipment within CoW. This is important when responsibility moves between shifts, different work teams, or upon job completion. The handover ensures that all parties are aware of the current status of the work, any residual hazards, and the integrity of installed controls.
The procedure requires documented confirmation that the incoming team understands the permit conditions and accepts responsibility for maintaining safety. When a job is complete, a final handover confirms that the work area has been cleaned and the equipment is ready to be safely returned to service.
Key Roles and Responsibilities
The successful operation of a CoW system depends on the clear assignment of organizational roles and accountability.
Issuing Authority
The Issuing Authority (or Area Authority) is typically a plant supervisor who controls the operational equipment and the work location. They are accountable for ensuring the asset is safe to work on and verifying that all pre-job checks and control measures are in place before formally issuing the permit.
Performing Authority
The Performing Authority is the individual responsible for the work team and the execution of the task at the worksite. They accept the permit, ensure the work team understands the scope, hazards, and required controls, and maintain safe work practices. This person is also responsible for initiating the formal close-out of the permit.
Work Team
The Work Team members are responsible for following the procedures outlined in the PtW, using the specified PPE, and exercising their stop-work authority if they believe conditions become unsafe.
Managing and Improving the CoW System
Control of Work is a dynamic system requiring continuous governance to maintain its effectiveness. Regular auditing and review are necessary to identify procedural weaknesses, compliance gaps, or emerging risks. These audits ensure that documented processes align with actual field practices and that safety standards are consistently applied.
Training and competency assurance are required for all personnel, especially those in Issuing and Performing Authority roles, ensuring they have the knowledge to correctly identify hazards and apply controls. The adoption of technology, such as digital Permit to Work systems, streamlines the process, enhances compliance tracking, and simplifies the process of making data-driven improvements.