HSG253
HSG253: the safe isolation of plant and equipment
Updated 2026
HSG253 is HSE guidance on the safe isolation of plant and equipment — ensuring machinery is positively isolated from all energy sources before maintenance. While HSG253 focuses on isolation procedures, knowing who is inside an isolated area, in real time, is a valuable additional control that supports permit-to-work and prevents re-energising equipment while people are still present.
- 1. HSE
- 2. HSE, HSG250
- 3. Industry standard
What HSG253 addresses
HSG253 sets out principles for the safe isolation of plant and equipment across the process industries. Positive isolation, proving isolation and secure lock-off are central themes.
It is closely linked to permit-to-work systems, which control high-risk activities and coordinate the people involved.
Personnel awareness as an added control
A recurring cause of serious incidents is re-energising equipment while a worker is still inside a machine or vessel. Zone awareness — knowing in real time whether anyone remains inside an isolated area — provides an independent check before energy is restored.
Integrated with permit-to-work, this gives supervisors confidence that the area is clear, complementing the physical lock-off that HSG253 describes.
The Salvus Safety Desk
HSE research & compliance team
The Salvus Safety Desk is our in-house health, safety and compliance team, drawing on frontline experience across COMAH, DSEAR and CDM sites to translate regulation into practical, real-time controls.
Frequently asked questions
Is personnel tracking a substitute for lock-off?+
No. Physical isolation and lock-off remain the primary control. Real-time zone awareness is an additional layer that helps confirm an area is clear before equipment is re-energised.
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