St. Charles County, MO Building Safety: Carbon Monoxide Detectors (2026)
Key Facts
- Governing code
- Property Maintenance Code, § 705.1
- County citation
- Section 500.500
- New dwellings standard
- Residential Code § R315
- Existing 1-2 family homes
- Battery-only alarm allowed
- Enforcement
- County Building Commission code official
Summary
St. Charles County requires carbon monoxide alarms in dwellings, tying the mandate to the county's Fire Code and Residential Code alarm-placement rules.
705.1 General. Carbon monoxide alarms shall be installed in dwellings in accordance with Section 1103.9 of the Fire Code of St. Charles County, except that alarms in dwellings covered by the Residential Code of St. Charles County shall be installed in accordance with Section R315 of that code for new dwellings. However, in one- and two-family dwellings interconnection is not required, and the power source is permitted to be solely battery operated in buildings that are not undergoing alterations, repairs, or construction of any kind.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4863880; v61 updated 2026-05-11; through 05-11-2026).
Full Breakdown
Under the Property Maintenance Code adopted at Section 500.500, dwellings must have carbon monoxide alarms installed per Section 1103.9 of the county Fire Code, or per Section R315 of the county Residential Code for new construction. In one- and two-family homes not undergoing alterations or construction, alarms don't need to be interconnected and can run solely on battery power. New construction and permitted alterations must meet the fuller Residential Code standard, including added alarms triggered by fuel-fired mechanical work.
Violations & Fines
Enforced by the County Building Commission's code official under the Property Maintenance Code abatement process (Section 500.510), which can order repairs and, for unresolved violations, pursue further remedies through the county's code enforcement hearing process.
Frequently Asked Questions
Do existing homes need hardwired CO alarms?
What triggers a CO alarm requirement during renovation?
Sources & Official References
Other rules in St. Charles County
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