AFCI
An arc-fault circuit interrupter is a breaker that opens the circuit when it detects the electrical signature of arcing, which is a common ignition source in residential fires.
What is AFCI?
An arc-fault circuit interrupter (AFCI) is designed to detect the irregular current pattern produced by an electrical arc — a loose connection, a damaged cord, or a nail driven through a cable — and cut power before that arc can start a fire. This is a different job from a GFCI, which protects people from shock. The National Electrical Code first required AFCI protection for bedroom circuits in the 1999 cycle and expanded it to most living-area circuits in later cycles, so what you should expect to find depends heavily on when the home was built or last rewired. Inspectors typically note whether AFCI protection is present, whether the devices trip when tested, and whether an older panel would make adding protection difficult. Absence of AFCI protection in an older home is normally reported as an upgrade opportunity rather than a defect, because codes are not retroactive.