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812 OSHA Focus Four Hazards
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Use Ground-Fault Circuit Interrupters (GFCI)

A "GFCI" is a ground fault circuit interrupter designed to protect people from severe and sometimes fatal electrical shock.

GFCI Outlet: How it works and how to test

A GFCI detects ground faults and interrupts the flow of electric current and is designed to protect the worker by limiting the duration of an electrical shock.

GFCIs monitor the current-to-the load for leakage to ground. When this leakage exceeds 5 mA ± 1 mA, the GFCI interrupts the current. They are rated to trip quickly enough to prevent electrocution. They should be inspected and tested monthly.

A Classic Example of the GFCI At Work

A homeowner is using an old drill with a loose bare wire inside it touching the outer metal housing. With the drill plugged in, the housing is charged with electricity. If it is used outside in the rain and the worker is standing on the ground, there is a path from the hot wire inside the drill through the worker to the ground. If electricity flows from hot to ground through the worker, it could be fatal. The GFCI can sense the current flowing through you because not all of the current is flowing from hot to neutral as it expects because some of the current is flowing through the worker to the ground. As soon as the GFCI senses a decrease in expected current, it trips the circuit and cuts off the electricity.

Knowledge Check Choose the best answer for the question.

8-4. What causes a ground fault current interrupter (GFCI) to trip?