What is Arc-Fault Circuit Interrupter (AFCI) protection, and where is it typically required in dwelling units?

• A. It detects arcing faults to prevent fires
• B. It protects against ground faults
• C. It is optional in dwelling units
• D. It detects arcing faults to prevent fires; required for most 120V, 15- and 20-amp branch circuits in dwelling units (per 210.12)

Answer: (D)

AFCI protection is about preventing fires by recognizing dangerous arcing faults in a circuit and quickly interrupting power. Arcing, from damaged insulation or loose connections, can heat conductors to ignite surrounding materials. AFCIs monitor the electrical waveform and trip when it detects arc signatures, reducing fire risk. In dwelling units, the NEC requires AFCI protection for most 120-volt, 15- and 20-amp branch circuits that supply outlets in living areas and bedrooms (per 210.12). This is different from GFCI protection, which protects against ground-fault shocks; AFCIs specifically target arcing faults and are mandated for typical residential circuits.