The Montreal Protocol, which entered into force on 1 January 1989, banned substances that threaten the ozone layer, including halogenated extinguishers, and prompted the search for new environmentally friendly agents, otherwise known as clean agents. The alternatives that exploit the same principle as the systems previously in use, the so-called "in kind" systems - use halocarbons extinguishing agents (halogenated hydrocarbon gases) or inert gases. Unlike some of those "not in kind” ones, which are based on different approaches (water-mist, foam, aerosol, etc.), they allow a fast and clean action resulting in the immediate resumption of activities after the intervention. All clean agent systems act on the oxygen available for the combustion reaction by diluting and/or "removing" it from the flame due to the difference between the various specific gas weights and by chemical-physical means, increasing the heat capacity of the atmosphere contained in the protected volume, which hinders heat propagation. Unlike inert gas systems, halocarbons also act chemically, capturing oxygen through the free radicals that are released via the decomposition of the extinguishing agent. Used for the protection of spaces where sufficient gas sealing can be achieved and, also for reasons of cost/benefit, gas systems are in particular used where it is not possible to use water (data centres, archives, electrical substations , libraries, warehouses and technical areas with personnel present).