How to put out a polystyrene fire?
An ABC extinguisher would be my choice I carry one on my truck and 2 in my boat. They will put out everything but electrical &amp; magnesium, kill the electrical first then the fire will not be electrical.
Magnesium takes a special chemical in the service it was called purple K .
ABC will put most things out quickly, last week we had a  Fire In a field just after a major power bump.
I was the first one there and with 1 medium fire extinguisher i was able to knock down the circle of about 40’ by using short controlled shots.
Where it started back up I was able to stomp it out, until our fire truck got there and we soaked the entire area down.
Even a small extinguisher can put out a decent sized fire with control. For home or office use I recommend ABC type extinguishers.