GFCI’s constantly monitor electricity flowing in a circuit. If the electricity flowing into the circuit differs by even a slight amount from that returning, the GFCI will quickly shut off the current flowing through that circuit. The advantage of using GFCI’s is that they can detect even small variations in the amount of leakage current, even amounts too small to activate a fuse or circuit breaker. GFCI’s work quickly, so they can help protect consumers from severe electric shocks and electrocution.