A Lockout Device holds an energy-isolating device (EID) in the safe position to prevent the energizing of a machine or equipment. Examples of EIDs include: circuit breakers, ball valves, or blind flanges.

Lockout devices must meet the following requirements:

• They must be used only for controlling energy.
• They must be durable and capable of withstanding the environment they are used in.
• They must be standardized by color, shape or size.
• They must be substantial enough to prevent removal (without the use of excessive force).
• They must identify the employee applying the device.