While many states adopt the NFPA or IFC Fire Code, city, county, or other municipal jurisdictions may have additional code requirements regarding smoke and carbon monoxide detectors. Most state laws do not limit municipality, county, or other local government authority from adding additional requirements to the State law.
While some states, such as Missouri, do not have statewide laws regarding carbon monoxide detectors or smoke alarms, cities, towns, and other local authorities within the state do have ordinances and laws. It’s always best to check ordinances and fire code laws on the state, county, and municipal levels.