  The Fredrickson-Andersen one spin facilitated model (FA-1f) on Z belongs to
the class of kinetically constrained spin models (KCM). Each site refreshes
with rate one its occupation variable to empty (respectively occupied) with
probability q (respectively $p = 1 - q$), provided at least one nearest
neighbor is empty. Here, we study the non equilibrium dynamics of FA-1f started
from a configuration entirely occupied on the left half-line and focus on the
evolution of the front, namely the position of the leftmost zero. We prove, for
q larger than a threshold $\bar{q} < 1$, a law of large numbers and a central
limit theorem for the front, as well as the convergence to an invariant measure
of the law of the process seen from the front.
