Q: How far away would you have to be from a car bomb (the kind that is detonated by starting the car) to survive with injuries and what sorts of injuries might you sustain in the blast?
A: This is a question that is virtually impossible to answer with any degree of accuracy. There are entirely too many variables involved. How big is the bomb? How big is the car? How close is close? What direction does the shrapnel fly and in which direction is the concussive force of the bomb directed? Are there any intervening walls or structures that might dampen the concussive force or block or redirect the shrapnel? Each of these variables, and many others, must be taken into account before any prediction of possible injuries can be entertained.
Lets look at a few general principles however. Big bombs cause big problems and little bombs cause less. A large bomb can produce a massive concussive force that will spread out for many yards in every direction. It can also produce shrapnel that can fly many hundreds of feet. A small bomb, needless to say, would release a smaller concussive force and any shrapnel would move at a slower rate and therefore do less damage.
Let's assume that this is a moderate sized bomb and the victim is standing close enough to receive injuries from the explosion. There are several types of injuries that can occur with a bomb.
If the person is close enough and the bomb is of the type that produces a great deal of heat, then burns over the skin and face can occur and even the victim's clothing might catch fire. This could produce severe injury to the flesh and the lungs.
The concussive force of the bomb is simply a wave of air molecules that are accelerated to very high speed. When the wave strikes an object or a person, damage and bodily trauma will result. This is why a bomb will destroy a building, knock down a wall, or kill a person within the concussive umbrella. If the force is strong enough it can burst eardrums, cause sinuses within the nose and face to bleed, rupture the lungs, rupture the abdomen and internal organs, and many other nasty injuries. If the person is slightly further away, or if the concussive force is dampened somewhat, then injuries to the eardrums and sinuses may occur but the other more severe injuries to the lungs and internal organs might not occur.
Shrapnel presents a very difficult and dangerous situation. With a car exploding all types of shrapnel can be fired in every direction. Chunks of metal and glass, complete doors or windows, beams of metal and even the engine can be launched in any direction. The types of injuries that someone would suffer depends upon exactly what strikes them, where they are struck, and with what speed and force they are hit. I think it would be obvious that if a car door or engine or some large piece of metal struck someone at very high velocity it would most likely kill them instantly and if not their injuries would be so severe that without very aggressive medical treatment and luck they would die from these in short order. But what about smaller pieces of glass and metal? These can penetrate the head, the chest, or the abdomen and damage vital organs and lead to death very quickly. Or they can enter the same areas and lead to massive injury and bleeding, which can then lead to death in minutes to an hour or so. Or they could simply be flesh wounds and the person could survive but would likely require surgical repair of the wounds and treatment with antibiotics to prevent secondary infections.
You can see almost anything can happen in this explosive situation. A large explosion at a great distance could easily do the same damage as a smaller one where the person was standing close by. Any bomb where the concussive force and shrapnel were directed away from the person might produce no injuries while if the victim were standing in the path of the concussive wave and the shrapnel he could be killed instantly. And anywhere in between. This great degree of variation in what actually happens is good for storytelling since it means that you can craft your story almost any way you want.
