Inergen

Fire extinguishing by means of a gas.
Inergen is used in spaces full of electrical equipment like process computers.
In every unit a battery of bottles like these are installed near the room where all the electric process equipment is installed.
Inergen is used at design concentrations of 40-50% to lower the concentration of oxygen to a point that cannot support combustion.

Here is the complete battery with instructions how to use and test.
When the system goes off a alarm sounds, the ventilation in that particular space stops and a few seconds later it is blown in....