What is an AFCI?
Starting January 1, 2002, The National Electrical Code, Section 210-12, requires that all branch circuits supplying 125V, single phase, 15 and 20Amp outlets be installed in dwelling unit bedrooms and that they be protected by an arc-fault circuit interrupter.
The AFCI (Arc Fault Circuit Interrupter) breaker will shut off a circuit in a fraction of a second if arcing develops. The current inside of an arc is not always high enough to trip a regular breaker. You must have noticed a cut or worn piece of a cord or a loose connection in a junction box or receptacle arcing and burnt without tripping the regular breaker. This is a major cause of fires in a dwelling.
There is a difference between AFCIs and GFCIs. AFCIs are intended to reduce the likelihood of fire caused by electrical arcing faults; whereas, GFCIs are personnel protection intended to reduce the likelihood of electric shock hazard.