In electrophotography, high humidity can trigger “deletion” characterized by mainly a blur or a density reduction of print images. In the recent survey we researched this phenomenon and found out the following mechanism. The main causing agent for “deletion” is ammonium compound of which deliquescence makes the surface resistance lower. Therefore we developed a novel method to measure a surface resistance and showed the correlation among surface resistivity ρs, amount of ammonium ions NH₄⁺ on a surface of a photoreceptor and CTF (Contrast Transfer Function) which was introduced to quantify image deterioration caused by “deletion”. With their results found out in this study and other observations we obtained before, we have built the 5-steps of deletion occurring framework from the viewpoint of printing-systems.