This thesis consists of three main parts. In the first part, the general procedures and principles of decontamination, the decontamination substances and mixtures, as well as the technique that is used for decontamination, have been described. Next, the description of the decontamination of the first responders, as this part of the decontamination process has been given; it has been elaborated and checked in practice. In the second part, there is the drafted plan of the mass extemporaneous decontamination of people in the selected public facility, according to the general methods of decontamination. Next, there is the drafted documentation for resolving an extraordinary event: an accident with subsequent leakage of a dangerous chemical substance, resulting in the need to carry out the mass decontamination of people in selected public facilities. In the last part, I have discussed and compared the advantages and possible disadvantages of the selected object of for the implementation of mass decontamination of people. There is also a suggested way of how to carry out this decontamination in this object in the most efficient way. The processing of this documentation has clearly confirmed my hypothesis. The mass decontamination of people in the selected location, in this case specifically in the Domazlice Hostel and Swimming Pool, can be feasibly performed with an improvised method. After giving the specific supplemented data (the names of the personnel, the telephone numbers, places of storage material etc.), the suggested documentation is usable for the object in practice. The documentation can be also easily adapted to other similar public facilities.