We report on the performance of the statistical, X-ray absorption lines identification procedure xline-id. As illustration, it is used to estimate the time averaged gas density n H (r) of a representative AGN's warm absorber (T ≈ 10 5 K) X-ray simulated spectrum. The method relies on three key ingredients: (1) a well established emission continuum level; (2) a robust grid of photoionization models spanning several orders of magnitude in gas density (n H ), plasma column density (N H ), and in ionization states; (3) theoretical curves of growth for a large set of atomic lines. By comparing theoretical and observed equivalent widths of a large set of lines, spanning highly ionized charge states from O, Ne, Mg, Si, S, Ar, and the Fe L-shell and K-shell, we are able to infer the location of the X-ray warm absorber.