I think it can act as an explosive, rather than a propellant like Pyrodex or nitro. So accidental ignition can result in an explosion rather than a fire. It was used as a blasting material for hundreds of years and I believe the 'power-monkey' had a relatively short lifespan. Monkey make mistake tamping it down, Monkey go 'BOOM'.
Here is some info on differences
http://www.chuckhawks.com/difference_black_powders.htm