The small homemade bomb that was just detonated in New York City was powerful enough to blow a large steel dumpster across the street. It was made according to a recipe published in a reputed Al-Qaeda magazine and was basically of the same design as the one used by the Boston marathon bombers and others around the world. It was housed in a freely available kitchen device — a pressure cooker. But why use a pressure cooker instead of some other container?
A pressure cooker is a tightly sealed container that allows its internal pressure to rise as the liquid inside it boils. But since the steam cannot escape, the pressure rises, which in turn makes things a lot hotter. It raises the boiling point of water from 212° F (100° C) to as much as 250° F (131°C). Now consider that the stuff inside is not tonight’s veggies, but rather an explosive such as TNT or black powder with shrapnel such as ball bearing or nails. Instead of exploding at the ambient temperature and pressure, the high temperature and pressure release at detonation makes the explosion ever more powerful and deadly.