A GFCI outlet contains a sensor that monitors the flow of the electrical current through the wires, and when it senses a ground fault (in electrical terms, “fault” means any variation from the normal current), the GFCI, which also contains an internal switch, shuts off the flow of electricity in the outlet.

In short, GFCI outlets exist to protect people from electrical shock — it is completely different from a house fuse.

Unlike a home's fuse, the GFCI is integrated in the outlet itself. When you plug in an appliance, such as a hair dryer, the GFCI outlet monitors the amount of power going to the device. If you accidentally drop the appliance into sink full of water, the GFCI detects the interruption in current and cuts the power immediately.

So how do you know if you're looking at an outlet equipped with GFCI capabilities? You'll see a TEST and a RESET button (and perhaps an indicator light) built right into the outlet.

To test the GFCI receptacle after installation, plug something into the outlet (like a radio or light) and turn it on. Press the “TEST” button on the GFCI to ensure the “RESET” button pops out, and the device turns off. If the “RESET” button pops out, but the light does not go out, the GFCI has been wired improperly. If the “RESET” button does not pop out, the GFCI is defective and should be replaced. Pressing the “RESET” button re-activates your circuit. You can also purchase inexpensive GFCI-compatible circuit testers.

Where GFCIs Are Required? GFCI protection for 15A & 20A 125-volt receptacles in bathrooms, kitchen, garages, crawl spaces, basements, laundry rooms and areas where a water source is present.