A method is provided for operating a gas concentration monitoring system as well as a gas-measuring device, a central unit, a gas concentration monitoring system as well as computer program product. The safety of persons or the safety of a situation is determined with respect to at least one hazardous gas. The concentration of the gas is provided to a memory and analysis device. A measured value rating number is determined for a preset period of use. A number of instances, of the measured concentration values exceeding of a preset gas concentration limit value is input. A safety code is determined from at least one of: the measured concentration values, the measured value rating numbers and from the a total number of instances in which a gas concentration limit value was exceeded.