Mesa, AZ Fire Regulations: Smoke Detectors (2026)

6 to set the power source standard for every smoke alarm installed under the chapter: 'Smoke alarms shall receive their primary power from the building wiring where such wiring is served from a commercial power source and, where primary power is interrupted, shall receive power from a battery. ' In practice that means new construction and covered alterations must hardwire smoke alarms into the branch circuit rather than relying on batteries alone, with the battery only serving as backup during a power outage. The section carries two narrow exceptions: smoke alarms may be battery-operated where installed in a building with no commercial power at all, and alarms added under an alteration or repair project may stay battery-powered if the work doesn't remove interior wall or ceiling finishes and there's no accessible attic, crawl space, or basement to run wiring through. 6, and both sections sit inside the same adopted-and-amended residential code chapter that governs one- and two-family dwelling construction citywide.