I had a short circuit in a Truimph TR7 car, a few wisps of grey smoke form behind the dashboard. I jumped out, grabbed a spanner i had in the boot and disconnected the battery. All that took was about 5-7 seconds.
The cabin by that time was filled with a grey acrid smoke, one whiff of which i caught as i opened the door took my breath away. If i where in that cabin i would be dead within a few seconds.
I had a Cessna ldg light switch short out, known for doing that, again a few wisps of cigarette type smoke, i gave very quick call to ATC and switched off the master switch and landed asap.
I wouldn't trust an aircraft fire extinguisher, used a dry powder twice to put fires out, useless. Just watch those motor racing crash videos.