Thornton, CO Fire Regulations: Smoke Detectors (2026)

6 sets the power-source standard for smoke alarms: primary power must come from the building wiring where a commercial source serves it, with a 10-year battery kicking in if that power is interrupted, and the wiring must be permanent, without any disconnecting switch beyond what overcurrent protection requires. 2 are likewise allowed to be battery powered. 4, permits combination smoke and carbon monoxide detectors to substitute for stand-alone smoke detectors in a fire alarm system, provided they carry both a UL 268 and UL 2075 listing, with battery-powered units rated for the device's full service life.

Both sections sit within Section 10-165, Thornton's amendments to the International Residential Code adopted at Section 10-164. Separately, the city's property maintenance provisions for existing hotel, motel and Group I-1 institutional buildings, Section 10-280(b), require single- and multiple-station smoke alarms in sleeping rooms and egress paths, with placement rules keeping ionization alarms at least 20 feet and photoelectric alarms at least 6 feet from a cooking appliance, and at least 3 feet from a bathroom door. Compliance with the alarm and power-source rules is checked by the Thornton Building Official during the same permit and inspection process that governs the rest of the Residential and Building Codes, and noncompliant work will not clear final inspection.