  We present a mean-field theoretical study on the effect of a single
non-magnetic impurity in quasi-one dimensional unconventional density wave. The
local scattering potential is treated within the self-consistent $T$-matrix
approximation. The local density of states around the impurity shows the
presence of resonant states in the vicinity of the Fermi level, much the same
way as in $d$-density waves or unconventional superconductors. The assumption
for different forward and backscattering, characteristic to quasi-one
dimensional systems in general, leads to a resonance state that is double
peaked in the pseudogap. The Friedel oscillations around the impurity are also
explored in great detail, both within and beyond the density wave coherence
length $\xi_0$. Beyond $\xi_0$ we find power law behavior as opposed to the
exponential decay of conventional density wave. The entropy and specific heat
contribution of the impurity are also calculated for arbitrary scattering
strengths.
