This bachelor theses looks at radioactive radiation and its detection with the help of dosimeters. The goal of the bachelor thesis was the comparison of the approach of HaZZ members at a selected real mission, at which a ionizing radiation was detected, with theoretical principals applied at a mission, as they are defined in the HaZZ standard code of practice, containing tactical-methodical procedures at a mission and identification of potential critical parts at these missions. For the purposes of this bachelor theses, we have used scientific methods of analysis and synthesis and subsequently with the goal of identification of potential critical parts in a mission of HaZZ members we have used the method of comparison. The outcome of the bachelor theses is the comparison of the procedure of HaZZ members at a selected real mission with the tactical-methodical procedure described in the standard code of practice. With the help of comparison, we have identified some unfulfilled principles and therefore the specific mission can be seen as wrong from the tactical point of view. In the next chapter we recommend changes and additions to the standard code of practice, which could improve missions, where ionizing radiation is present.