Absorption measure distribution in AGN can be determined since we are able to see absorption lines on highly ionised elements with CHANDRA/XMM-Newton precision. AMD is best tool to measure the global distribution of this warm gas which interacts with radiation coming from the nucleus. The observed deeps in AMD are well explained by the eventual thermal instability in caused by strong gas irradiation with hard X-rays. I will present how the distribution of absorbed gas depends on gas physical parameters and what has the biggest influence on the location of observed deeps and AMD normalisation. I will discuss the best warm absorber model which explains the observed AMD shape in currently available sources. Some questions that arise are:
- What is the main difference in the cloud sructure between Radiation Pressure Confinement and Constant Total Pressure?
- What main physical parameter or physical process are responsible for the AMD normalization?
- Can thermal instability caused by illumination create the wind in AGN?
- Do AGN winds remain static or stationary in the gravity field of central BH?