An installation for testing open fire extinguishing systems includes a smoke and/or mist generator and a connecting conduit suitable and dedicated for being connected to a fire fighting system. A method for testing of fire extinguishing systems has the following steps performed in any suitable order: a) providing an installation for the generation of smoke and/or mist, b) connecting a conduit of the installation to a conduit of a first section of a preferably open fire extinguishing system, c) opening a valve which provides a connection between the first section of the fire fighting system and the connecting conduit of the installation, d) turning on the smoke and/or mist generator, such that, by the exiting of the smoke and/or mist, the spray heads of the first section of the fire extinguishing system can be inspected on their openness, e) repeating steps b-d for any further section of the fire extinguishing system.