The theoretical part of the bachelor thesis "Danger of oxidizing substances" deals with the definitions of oxidizing substances, transport, labeling and safe handling of such substances. Thesis also presents extraordinary events caused by oxidizing substances in the Slovak Republic and in the world. In the practical part there is an overview of oxidizing substances occurring in the Slovak Republic in companies falling under the Act on the prevention of industrial accidents. We further defined selected oxidizing substances (oxygen, chlorine, nitric acid, hydrogen peroxide, sodium nitrite and ammonium nitrate), while describing their basic properties, hazard identification, occurrence and use. The work also contains a summary of data, the classification of oxidizing substances according to the number of SEVESO enterprises in the territory of the Slovak Republic in which these substances occur and also an overview of all SEVESO enterprises with the presence of oxidizing substances.