Explosion Modifer, how do you control the area of the Modifier?

I have noticed with the Explosion modifier, there is an area in which the particles can go and they stick on an invisible wall, or the camera. Is there a way to expand this area out so the particles go further (out of camera view). I am newb to Blender, so if there is a tutorial i haven’t read or seen on this, I’ll be happy to review if someone can point me into the right direction.

In the particle system used for the explode modifier the distance of the particles is determined by their initial velocity and the lifetime of the particles. If the lifetime is too short the particle will die before it hits the ground.