GFCI
A ground-fault circuit interrupter, a device that cuts power when it detects current leaking to ground, protecting people from electric shock.
What is GFCI?
A GFCI compares the current leaving on the hot conductor with the current returning on the neutral. A difference of roughly five milliamps indicates current is finding another path — often a person — and the device opens in a fraction of a second. Code has progressively expanded required locations since the 1970s: exterior receptacles first, then bathrooms, garages, kitchens, crawl spaces, unfinished basements and laundry areas, and more recently additional locations in each cycle. Inspectors test the devices, confirm that protection actually extends to the downstream receptacles it is supposed to cover, and check for the common miswire in which line and load terminals are reversed so the test button works but downstream protection does not.