Where is AFCI (arc-fault) protection required in a house?

AFCI protection is required on 120-volt branch circuits serving outlets in most living areas — kitchens, bedrooms, living/family/dining rooms, hallways, closets, and laundry areas (IRC E3902.16).

The IRC requires arc-fault circuit-interrupter (AFCI) protection on 120-volt, 15- and 20-amp branch circuits that supply outlets in kitchens, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, and laundry areas — essentially most habitable and adjacent spaces.

Protection is provided by a listed combination-type AFCI breaker or one of the listed outlet-branch-circuit arrangements. The section number moves by edition: it is E3902.12 in the 2012 IRC and E3902.16 in the 2015 IRC, and later editions renumber again and broaden coverage.