That really depends on how much has been ignited. If you have a small pile, I agree that it's most likely to burn out before you even get to the thing and pull the key.
let an opened can, measure, or plate full of powder for dipping charges, you may have a lot of powder ignited and going when you hit it with the high pressure propellant. That's going to be dangerous. for a time, I kept my supply in another room, but I eventually realized that the safest place for it was far away from the cans of mineral spirits, stripper, water heater, etc. The second extinguisher is a powder.
Lemme mention a huge mistake I made once. I was working at my bench. I had a steel wool pad on my bench behind and to the right of my grinder. I used the grinder, went about my business, and almost ten minutes later went back to find that steel wool pad still smoldering. that could have erupted into flame.
You really can't be too careful.