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The danger of injury through electrical shock is possible whenever electrical power is
present. When a person's body completes a circuit and thus connects a power source with the ground, an electrical burn or injury is imminent. Most fatal injuries result from high-voltage exposure; however, people can sustain severe injuries from low voltage power if it has a high current flow.

Electrical safety is important in every work environment. The following sections cover circuit breaker loads, electrical grounding, electrical safety guidelines, and electrical emergency response.

2. Electrical Definitions

The following definitions help clarify general electrical safety:

Amps: the standard unit for measuring electrical current.

Watt: a unit of electrical power, equal to the power developed in a circuit by a current of amp flowing through a potential difference of one volt.

Voltage: electromotive force expressed in volts.

Circuit Breaker: a device that automatically interrupts the flow of an electrical current.

Breaker Box: an insulated box on which interconnected circuits are mounted.

Electrical Panel: an insulated panel on which electrical wires are mounted.

Current Flow: the rate of flow of an electrical charge, generally expressed in amps.

Electrical Load: the amount of power delivered by a generator or carried by a circuit. A device to which the power is delivered.

Ground-Fault Circuit Interrupter (GFCI): a GFCI detects grounding problems and shuts electricity off to prevent a possible accident.

High Voltage: the term high voltage applies to electrical equipment that operates at more than 600 Volts (for terminal to terminal operation) or more than 300 Volts (for terminal to ground operation). Low voltage, high current AC or DC power supplies are also considered to be high voltage.

Hazardous Energy Sources: this term applies to stored or residual energy such as that in capacitors, springs, elevated machine members, rotating flywheels, hydraulic systems, and air, gas, steam, or water pressure

Lockout: the placement of a lock on an energy-isolating device. This act prevents workers from operating a piece of equipment until the lock is removed.

Tagout: the placement of a tag on an energy-isolating device. A tagout device is a prominent warning device of a lockout.

Energy-Isolating Device: a mechanical device that prevents the transmission or release of energy. Examples include the following:

  • Manually operated circuit breakers
  • Disconnect switches
  • Line or block valves
  • Pushbuttons, selector switches, and other control circuit devices do not isolate energy.

Energy-isolating devices should be lockable by means of a hasp or other type of
attachment. It should not be necessary to dismantle or reassemble a device to lock it.

Authorized Employee: a person who locks out or tags out equipment for service or maintenance. Authorized employees have been formally trained in proper lockout/tagout procedures.