  This study investigates the properties of two gas structures of X-ray
selected active galactic nuclei (AGNs), that is, dusty and dust-free gas
components, by separating them with the line-of-sight dust extinction ($A_V$)
and the neutral gas column density ($N_{\mathrm{H}}$). The typical column
density of the dusty and dust-free gas differs depending on the Seyfert type,
indicating that both structures have anisotropic column density distributions.
The number of targets with the dusty gas column density ($N_{\mathrm{H,d}}$) of
$\log N_{\mathrm{H,d}}\ [\mathrm{cm^{-2}}]>23$ is much smaller than that with
the same column density of the dust-free gas. This result indicates that the
optically-thick part of the dusty gas structure is very thin. There are very
few targets with a larger Eddington ratio ($f_{\mathrm{Edd}}$) than the
effective Eddington limit of the dusty gas and the covering factor of the dusty
gas with $22\leq \log N_{\mathrm{H,d}}\ [\mathrm{cm^{-2}}]<24$ exhibits a clear
drop at the effective Eddington limit. These results support the scenario
wherein the covering factor of the dusty torus decreases in a high Eddington
ratio owing to the radiation-driven dusty gas outflow. The covering factor of
the dust-free gas with the column density ($N_{\mathrm{H,df}}$) of $22\leq \log
N_{\mathrm{H,df}}\ [\mathrm{cm^{-2}}]<24$ similarly exhibits the decrease in
high Eddington ratio, although it may be owing to the dust-free gas outflow
driven by certain other mechanisms than the radiation pressure. Finally, we
propose an updated picture of the AGN gas structure based on our results and
the literature.
