Ada County, ID Building Safety: Carbon Monoxide Detectors (2026)

Ada County Code 7-2-5 adds carbon monoxide alarm requirements to Chapter 12 "Mechanical Administration" of the adopted 2018 International Residential Code, since the base IRC edition the county adopted did not carry a standalone carbon monoxide section for the building division to enforce. Section M1203.1 requires an approved carbon monoxide alarm outside of each separate sleeping area, in the immediate vicinity of the bedrooms, in any dwelling unit that either has a fuel-fired appliance, such as a gas furnace, water heater, or fireplace, installed or has an attached garage. The requirement applies to new construction reviewed and permitted by Ada County.

Section M1203.2 extends the same duty to existing homes: whenever work requiring a permit occurs in an existing dwelling that has an attached garage, or that already has a fuel-fired appliance, the owner must add carbon monoxide alarms in accordance with section R315 as part of that permitted project. A kitchen remodel, an addition, or an attached-garage conversion that pulls a building permit is the trigger; an untouched older home with no active permit has no independent retrofit deadline under this section.

Section M1203.3 sets the equipment standard: alarms must be single-station units listed as complying with UL 2034, and installed both to the code and to the manufacturer's own installation instructions, so placement height, spacing from cooking appliances, and any interconnection requirements printed on the listing label are enforceable. Ada County Development Services checks for compliant alarms during plan review and inspection before issuing a certificate of occupancy on covered projects.