GFCI (Ground Fault Circuit Interrupter): An electrical outlet or circuit breaker that monitors current flow and automatically shuts off power within milliseconds when it detects a ground fault (unintended current path to ground), protecting against electric shock.
How GFCIs Work
A GFCI constantly monitors the difference between current flowing out on the hot wire and current returning on the neutral wire. When those currents differ by more than about 5 milliamps — indicating current is taking an unintended path, possibly through a person — the GFCI trips and cuts power in 1/40th of a second. This is fast enough to prevent fatal electrocution in most cases.
Where GFCIs Are Required by Code
The NEC (National Electrical Code), adopted in most U.S. jurisdictions, requires GFCI protection in: all kitchen countertop outlets within 6 feet of a sink, all bathroom outlets, garage outlets, unfinished basement outlets, exterior outlets, pool and spa areas, crawl spaces, boathouses, and any outlet near a bathtub or shower. Requirements have expanded with each code update — older homes may not have GFCIs where current code requires them.
GFCIs and Permit Inspections
When pulling an electrical permit for remodeling work, inspectors verify GFCI protection in all required locations — including any locations that are disturbed or affected by the work. In many jurisdictions, electrical work in a kitchen or bathroom automatically triggers a requirement to bring all outlets in the room up to current GFCI standards, even if those outlets weren't part of the original scope.
GFCI vs. AFCI
GFCIs protect against ground faults and electric shock. AFCIs (Arc Fault Circuit Interrupters) protect against arc faults that can cause fires. Current codes require both in many locations. AFCIs are required in bedrooms, living rooms, and most other habitable spaces in new construction. GFCIs are required in wet and exterior areas. Some locations require dual-function GFCI/AFCI protection.