write down special reminders in PREPARING SOLUTIONS?
CO2and I'm saying that only because you don't get water all over the place. If your DT is on fire, it really doesn't matter what you use as long as you put the fire out because at that point, your PC and everything in it is toast.
Because oil floats on top of water (so the fire won't go out. it'll just float), and because water conducts electricity (so you'll probably get electrocuted).
A regular dry-chemical ABC extinguisher would work, but you're going to make a hell of a mess putting the fire out. While the desktop may be toast, your going to ruin anything else of an electronic nature in the vicinity (printer, scanner, modems, routers, etc.) CO2 would also not be a bad choice, but CO2 doesn't have the 'A' rating and there is a high degree of reflash.