  Different approaches to quantum gravity conclude that black holes may possess
an inner horizon, in addition to the (quantum corrected) outer `Schwarzschild'
horizon. In this paper we assume the existence of this inner horizon and
explain the physical process that might lead to the tunneling of particles
through it. It is shown that the tunneling would produce a flux of particles
with a spectrum that deviates from the pure thermal one. Under the appropriate
approximation the extremely high temperature of this horizon is calculated for
an improved quantum black hole. It is argued that the flux of particles
tunneled through the horizons affects the dynamics of the black hole interior
leading to an endogenous instability.
