  We present a brief review of the non-Abelian tensor gauge field theory and
analyze its free field equations for lower rank gauge fields when the
interaction coupling constant tends to zero. The free field equations are
written in terms of the first order derivatives of extended field strength
tensors similar to the electrodynamics and non-Abelian gauge theories. We
determine the particle content of the free field equations and count the
propagating modes which they describe. In four-dimensional space-time the
rank-2 gauge field describes propagating modes of helicity two and zero. We
show that the rank-3 gauge field describes propagating modes of helicity-three
and a doublet of helicity-one gauge bosons. Only four-dimensional space-time is
physically acceptable, because in five- and higher-dimensional space-time the
equation has solutions with negative norm states. We discuss the structure of
the particle spectrum for higher rank gauge fields.
