Tempe, AZ Building Safety: Carbon Monoxide Detectors (2026)

6 is the city's own rule on how carbon monoxide alarms must be powered. It requires that a CO alarm receive its primary power from the building's electrical wiring wherever that wiring is fed from a commercial power source, switching to battery power only when the primary circuit is interrupted. The wiring feeding the alarm has to be permanent and cannot have any disconnecting switch besides the breaker or fuse protecting the circuit from overcurrent, so the alarm cannot be shut off at a wall switch.

Two exceptions exist. A CO alarm may run on battery power alone if the building has no commercial electric service at all. 2 can also keep an existing battery-only CO alarm if the work does not remove interior wall or ceiling finishes, unless an attic, crawl space or basement is open and accessible for running new wiring, in which case hardwiring becomes mandatory again. The Tempe Building Safety Division verifies this at the permit and final-inspection stage for new single-family and two-family dwellings, additions, and any remodel that opens wall or ceiling cavities near fuel-burning appliances or attached garages.

Because the requirement lives in the adopted residential building code rather than the fire code, compliance is checked when a permit is pulled and inspected, not through routine inspections of homes already occupied. 6, adopted in the same ordinance.