St. Clair County, IL Building Safety: Carbon Monoxide Detectors (2026)

Building Regulations Sec. 7-2-71 requires every dwelling unit, including each unit of a multi-family or mixed-use building, to have at least one approved carbon monoxide alarm in operating condition within 15 feet of every room used for sleeping purposes. The alarm must meet Illinois State Fire Marshal rules and bear a nationally recognized testing laboratory label (UL or CSA standards); it may be combined with a smoke detector if the combined unit still clearly differentiates the two hazards. Alarms may be battery powered, plug-in with battery back-up, or hardwired into AC power with secondary battery back-up, but new construction alarms must be interconnected with the smoke detector and be both 110-volt and battery-backed.

The owner of the structure must supply and install every required alarm and give at least one tenant per dwelling unit written instructions on testing and maintenance; the owner must also ensure batteries are working when a tenant takes possession. The tenant is responsible for day-to-day testing, general maintenance and battery replacement, and must notify the owner in writing of any deficiency the tenant cannot fix; the owner or agent must then be given access to correct it. Two narrow exemptions exist: a unit that does not rely on fossil-fuel combustion for heat, ventilation or hot water, is not connected to a garage, and is not close enough to a carbon monoxide source to receive it; or a unit the local building commissioner otherwise determines is not close enough to any carbon monoxide source to be at risk.