controlled demolition is not an accident

http://en.wikipedia.org/wiki/Building_implosion

[...]Detonation

Nitroglycerin and any dilutents can certainly deflagrate, i.e. burn. However, the explosive power of nitroglycerin is derived from detonation: energy from the initial decomposition causes a pressure wave or gradient that detonates the surrounding fuel. This is a self-sustained shock wave that propagates through the explosive medium at some 30 times the speed of sound as a near-instantaneous pressure-induced decomposition of the fuel into a white hot gas. Detonation of nitroglycerin generates gases that would occupy more than 1,200 times the original volume at ordinary room temperature and pressure. Moreover, the heat liberated raises the temperature to about 5,000 °C (9,030 °F).[10] This is totally different from deflagration, which depends solely upon available fuel regardless of pressure or shock.[...]

http://en.wikipedia.org/wiki/Nitroglycerin 

http://en.wikipedia.org/wiki/Dynamite 

http://en.wikipedia.org/wiki/Nobel_Prize