Isn’t the use of water for extinguishing a fire caused by thermal oil dangerous?

A direct water jet to extinguish the fire would be dangerous. It could evaporate instantaneously if it contacts the heat of the thermal oil leakage and cause damage.
Therefore, the NESS extinguishing system counts on a very fine water mist that forms an inert pad on the fire and smothers it. The water mist is sprayed by a special nozzle that is moved into the heater chamber if activated.