There are places in factories or offices where in case of fire we can not spray water, like Server rooms, Electric rooms etc. as it may damage costly equipments for ex. Servers, POE switches, Data racks etc.
We install battery of extinguishers outside such room and give the outlet in that room. In case of fire, The chemical agent filled in these cylinders sprayed on the area to diffuse the fire. It is harmless and it doesn’t damage electronic equipments.