Back in high school, the fire brigade came to refill and test all the extinguishers.
One of the firemen put a few inches of water in a bucket, then gave the inside of the bucket a long burst out of a CO2 extinguisher.
Then got me to touch the surface of the water.
The big fat spark that got me REALLY hurt!!
That was when he told us about the dangers of using a CO2 extinguisher on flammable liquids, gas leak fires or fine powder fires.
This is why you won't find CO2 extinguishers in grain silo's, grain elevators or flour mills.