The National Electrical Code requires ground fault circuit interrupter (GFCI) protection of receptacles located outdoors, in bathrooms, garages and spa areas. This applies not only to new construction, but also to existing homes. The GFCI circuit interrupter provides protection against overloads, short circuits and ground faults. It detects very low levels of electrical current leakage (ground faults) and acts quickly to shut off power, preventing serious shock.