What is the main cause of injuries?

What ingredients in a bomb cause blast injuries?

• In an instant, an explosion or blast can wreck havoc; producing numerous  casualties with complex, technically challenging injuries not commonly seen after natural disasters such as floods or hurricanes.

• Answer:

  Rather than a specific ingredient or list of ingredients, it's the physical/chemical process of explosion that causes the injuries. Taking a simple example, black powder (currently assumed to be the explosive used in the Boston Marathon bombings) is easy to make: a child can do it. It calls for the mixture of three, relatively-easy-to-acquire chemicals. If you put a pile of black powder on the ground and drop a match on it, it will burn, creating a lot of smoke, sparks, and a fizz. If you're too close, you get burned by the combustion. If, instead, you put that powder into a tight container, the combustion is restricted. As the powder burns, it produces gases. The gases expand (all that smoke from the free-burning powder). If the container is strong enough, nothing much happens -- the explosion is contained. If it's not strong enough, it explodes creating a shock wave as the gas pressure is suddenly released. The pressure may cause the container to fragment, creating shrapnel as was the case in Boston. If there's a way for the expanding gases to escape, you may end up with a sky rocket as the gas pushes in one direction and the rocket moves in the other. If there's something somewhat tightly sealed at one end of the container, then it flies out, like a bullet. The amount of explosive and the speed at which is burns within a sealed container will determine what kind of injuries result. It could be as minor as a small firecracker bursting in and burning the fingers or a larger one taking off the fingers. Larger amounts can take off an arm or launch shrapnel into the body. A large explosion can readily burst eardrums. A very large explosion can kill by compressing the air in the lungs, intestines, or brain through overpressure. Overpressure can also break bones. An explosion can burn one seriously or fatally. If it's big enough and you're close enough, you can be blown to pieces.