Senate committee substitute to the 1st edition amends the requirement in GS 115C-12 to now require the adoption of rules applicable to all public school units that require existing school buildings to be equipped with carbon monoxide alarm and detection systems in accordance with the requirements for new buildings under the specified building code section (was, have adequate carbon monoxide alarms, as defined, and new school buildings placed into service on or after July 1, 2025, must have adequate carbon monoxide detectors, as defined). Requires the installation of carbon monoxide alarm and detection systems to be permitted, installed, and inspected as required by the Building Code. Prohibits requiring an existing school building to be equipped with a carbon monoxide alarm and detection system if the system would not be required for a new building under the specified building code section.