A method for operating an automatic active safety system, for safe operation in outdoor or indoor work areas with respect to the presence of flammable and/or toxic gases, with operating means present in such areas, the system including: - one or more metering devices (8, 18) for measuring the amount of gaseous substance present in, or in proximity of said work areas; - a control unit for management of the system, connected by wired or wireless connection to said metering devices (8, 18) and provided with means for determining, based on the amount of gaseous substance detected in or in proximity of said work areas, levels of these flammable and/or toxic gases present in the same work areas corresponding to increasing hazard levels for the operators; - automatic active intervention means designed to signal the hazard level present in the same work areas to said operators, to activate visual and/or acoustic alarm means and to intervene, if necessary, on the operation of said operating means being used by said operators. said system being characterized in that: one or more fixed metering devices are also provided, which are located in one or more spots of greater hazard of said work areas and connected with a wireless connection to said control unit; as many portable metering devices are provided as operators are present, each portable metering device being supplied to a respective working operator and connected with a wireless connection to said control unit, said metering devices are associated with or embedded in PPE (personal protective equipment) provided to each working operator, characterized in that said fixed metering devices, in use, are also placed inside a pipe of the gas distribution network for which the installation, repair or maintenance is being performed, in a portion of said pipe to be restored, or in a container to be restored. - one or more metering devices (8, 18) for measuring the amount of gaseous substance present in, or in proximity of said work areas; - a control unit for management of the system, connected by wired or wireless connection to said metering devices (8, 18) and provided with means for determining, based on the amount of gaseous substance detected in or in proximity of said work areas, levels of these flammable and/or toxic gases present in the same work areas corresponding to increasing hazard levels for the operators; - automatic active intervention means designed to signal the hazard level present in the same work areas to said operators, to activate visual and/or acoustic alarm means and to intervene, if necessary, on the operation of said operating means being used by said operators. one or more fixed metering devices are also provided, which are located in one or more spots of greater hazard of said work areas and connected with a wireless connection to said control unit; as many portable metering devices are provided as operators are present, each portable metering device being supplied to a respective working operator and connected with a wireless connection to said control unit, said metering devices are associated with or embedded in PPE (personal protective equipment) provided to each working operator, characterized in that said fixed metering devices, in use, are also placed inside a pipe of the gas distribution network for which the installation, repair or maintenance is being performed, in a portion of said pipe to be restored, or in a container to be restored.