St. Clair County, IL Fire Regulations: Smoke Detectors (2026)

St. Clair County wrote its smoke-detector mandate into the local amendments to the 2011 National Electrical Code (Sec. 7-7-13, item 9), the same amendment package that set the county's minimum 100-amp service size and arc-fault protection rules. The rule reaches every dwelling in the unincorporated county, not just new construction: detectors must be hard-wired with battery backup, interconnected so that one alarm trips them all, and installed in each bedroom, in the hallway outside bedrooms within fifteen feet, and on every level of the home. A smoke detector that is only part of a security system does not satisfy the requirement; it has to be a stand-alone, interconnected unit.

Carbon monoxide detectors are required alongside the smoke alarms in any dwelling that burns fuel for heat, cooking or hot water, or that has an attached garage. The CO detector must sit within fifteen feet of each bedroom door and must be wired into the same interconnected circuit as the smoke detectors, so a CO alarm anywhere in the house sounds every unit. The county's Electrical Inspector, part of the Building and Zoning Department, enforces the amendment alongside the rest of the adopted electrical code, and checks wiring and detector placement as part of the standard permit inspection on remodels and new construction covered by Sec. 7-1-27.