AFCI protection generally required in dwelling units?

• A. For most 120-volt, single-phase, 15- and 20-amp branch circuits in dwelling units, with some exceptions per edition.
• B. For all circuits regardless of amperage.
• C. Only in kitchens and bathrooms.
• D. For most 120-volt, single-phase, 15- and 20-amp branch circuits in dwelling units, with some exceptions per edition.

Answer: (D)

AFCI protection is used to stop fires caused by arc faults in branch circuits. The general rule is that most 120-volt, single‑phase, 15- and 20‑amp branch circuits in dwelling units should be AFCI protected, because these circuits feed outlets throughout living areas where arcing faults are more likely to occur. An AFCI device detects the distinctive electrical signature of dangerous arcing and interrupts the circuit to prevent ignition. This is different from GFCI protection, which guards against shock from ground faults.

The phrase “with some exceptions per edition” reflects that the exact requirements can vary between NEC code cycles. Some circuits may be exempt or subject to different rules depending on the edition of the code in force, so the general principle remains: AFCI protects most such dwelling-unit circuits, but the precise exemptions are edition-dependent.