The indication of atmospheric pollutant entries is an important task of biomonitoring. Due to their ability to absorb contaminants to a large extent, mosses are particularly well-suited for determining and assessing air pollution. In addition to conventional immission measurements which are mainly based on physico-chemical measurement methods, alternative methods are more frequently used, taking into account living organisms for monitoring the environmental situation, so-called bioindicators, and they allow an impact-related statement of the immission situation. The basis of the European Standard is passive biomonitoring with mosses. The actions that shall be taken from the field sampling of mosses to their final preparation before analysis for targeted contaminants are described. This European Standard applies to spatial and/or temporal biomonitoring of atmospheric contaminants. It is of interest to all operators wishing to conduct air quality biomonitoring studies.