The device comprises an assembly (3) for producing a hot gas flow under pressure having an outlet of hot gas, a nozzle (5) having a hot gas inlet connected to the hot gas outlet and an outlet for ejection of a liquid mist, a first liquid source (7), a unit for injecting a measured flow of liquid from the first source of liquid in the nozzle, a probe (11) for detecting a total or partial interruption of measured flow of liquid injected in the nozzle from the first liquid source, a second source (13) of liquid, and a unit to inject a flow of liquid relief from the second source of liquid. The device comprises an assembly (3) for producing a hot gas flow under pressure having an outlet of hot gas, a nozzle (5) having a hot gas inlet connected to the hot gas outlet and an outlet for ejection of a liquid mist, a first liquid source (7), a unit for injecting a measured flow of liquid from the first source of liquid in the nozzle, a probe (11) for detecting a total or partial interruption of measured flow of liquid injected in the nozzle from the first liquid source, a second source (13) of liquid, and a unit to inject a flow of liquid relief from the second source of liquid in the nozzle when the probe detects a total or partial interruption of measured flow of liquid injected into the nozzle from the first liquid source. The unit for injecting the measured flow of liquid comprises a fluid dispenser body having a liquid suction inlet connected to the first source of liquid and a liquid discharge outlet connected to an inlet of liquid of the nozzle. The unit for injecting the flow of liquid relief comprises a valve body for selectively connecting the liquid suction inlet of the dozer body to the second liquid source. The probe is able to measure a current temperature of the gas in the nozzle in downstream of the liquid inlet. A logic controller is arranged to collect current temperature of the gas measured by the probe, to compare the current temperature with a predetermin
