2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/15031Major flows of ionized gas are thought to be present in the nuclei of most luminous QSOs, and absorption by these flows often has a significant effect upon the observed X-ray continuum from the black hole region. We briefly discuss X-ray studies of this gas and attempts to determine its geometry, dynamics, and ionization physics. Our focus is on X-ray warm absorber QSOs, Broad Absorption Line QSOs, and soft X-ray weak QSOs. We also discuss some prospects for further study with the next generation of X-ray observatories.10 pages, to appear in the proceedings of the Bologna conference on "X-ray Astronomy 1999: Stellar Endpoints, AGN, and the Diffuse X-ray Background" (Astroph. Lett. and Comm.), also available from http://www.astro.psu.edu/users/niel/papers/papers.htmlAstrophysicstext