Abstract: A gas sensor module is coupled to a medical gas system in a healthcare facility to monitor gas type and/or gas flow. In some embodiments, the gas sensor module is coupled to a gas pipe of the medical gas system behind a wall, ceiling, floor, access panel, or the like and transmits an alarm signal to an alarm controller located elsewhere in the healthcare facility. In other embodiments, the gas sensor module plugs into a service outlet of the medical gas system. Also disclosed is a combination service outlet and gas sensor module. A main gas alarm module may communicate with one or more remote gas alarm modules.