In the present work we review the circumstances under which charged particles can escape black hole gravitational fields after its collision with another particle. Here we examine the dynamics of eutral and charged particles interacting with slowly and rapidly otating Kerr black holes in the presence of magnetic fields. In this respect, rotating black holes may act as particle accelerators under certain circumstances. Axially symmetric magnetic field homogeneous at infinity and other type of configurations are discussed. It is nalyzed the effective potential of the system, as well the center of mass energy and the escape velocity of the particles. As appointed by many examples in the literature, some of the main results point that the intensity of the magnetic fields induces the innermost stable circular orbit (ISCO) to be closer to the black hole horizon. There is a range of possible values for the spin a and for the magnetic field such that particles should escape from the system. The present investigation on particle escape velocity can possibly contribute, for example, to constrain AGN dynamic properties to properly understand the acceleration mechanisms of the highest energy cosmic rays in the universe.