In many parts of the country, electricians will soon begin installing a new type of circuit breaker: the arc-fault circuit interrupter, or AFCI. These safety devices are intended to detect the kind of electrical arcs that can cause fires. Both the 1999 and 2002 versions of the National Electric Code (NEC) require the installation, beginning January 1, 2002, of AFCIs on all residential bedroom circuits (NEC 210-12). What Do AFCIs Do? An AFCI will trip under different circumstances than a conventional circuit breaker or GFCI, neither of which is designed to protect a house from fire. The main purpose of a conventional circuit breaker is to protect wires from overheating, while GFCI breakers are intended to protect people from