From Unofficial Stationeers Wiki
Portable device to extinguish fires or fires of small magnitude. It extingishes a single object from being on fire, making it useful in protecting small areas. However against a large scale fire it is recommended to vent the area.
Use left-click while in active hand while pointing at object to use.
It can be used to cool a room by pointing it an object and holding the click, the room temperature will drop fast making it perfect for cheap quick cooling on worlds like Venus where you start with one.