TheGround Fault Circuit Interrupter (GFCI)is a life-safety device specifically designed to protect people from electrical shock. According toOSHA 29 CFR 1910.304, a GFCI works by constantly monitoring the current flowing through a circuit. It compares the amount of current going to an electrical component with the amount returning from it. In a normally functioning circuit, these two values should be nearly identical. However, if the GFCI detects a difference as small as 4 to 6 milliamperes—indicating that some of the current is "leaking" out of the circuit through an unintended path, such as a human body touching a conductive surface—it will break the circuit in as little as 1/30th of a second.

It is essential for disaster professionals to distinguish a GFCI from a standardCircuit Breaker(Option C). A circuit breaker is designed to protectequipment and the building structurefrom fires caused by overloads or short circuits; it typically only trips when the current exceeds 15 or 20 amperes. This level of current is far above the "let-go" threshold for humans and can be fatal. A GFCI, by contrast, is a "personnel protection" device.Voltage interrupters(Option A) is a generic term that does not refer to this specific safety technology.

In disaster management, GFCIs are mandatory for all temporary power setups, particularly in wet or damp environments common after floods or storms. Under theNational Electrical Code (NEC)andNFPA 70E, GFCIs must be used with portable generators and power tools on-site. TheCEDPcurriculum emphasizes that "stray voltage" is a major hazard in disaster zones. By ensuring all power sources are GFCI-protected, emergency managers mitigate the risk of accidental electrocution for both responders and victims who may be navigating flooded structures or using emergency power systems.