use of underground space for the storage of selected gases (cH 4 , H 2 , and co 2 ) -possible conflicts of interest introductionThe underground space has been used by people since ancient times. Initially, it was used as a shelter (caves) and for exploration and the exploitation of mineral resources and groundwater. The development of mining enabled the rock mass to be used for other purposes, such as transport, infrastructure, the storage of liquids and gases, substances, and waste (Przybycin et al. 2011;Evans et al. 2009).The limited land space and the safety of storage are the reasons for using underground structures. This is the case with shelters, data systems (e.g. documents, films, photographs), computer systems, etc. The most shallow facilities, offices and storage sites, are usually built up to about 10 m BGl (below sea level) (Figure 1). Social facilities (cultural and recreational spaces, railway, and subway stations) are located up to a depth of 20 meters. Industrial