The hazardous substances with their characteristics may cause life, health or property threatening. A leakage of any dangerous substance may occur in the process of its production, processing, transport or storage. In a case of the leak of a dangerous substance it is necessary to find out what kind of dangerous substance has leaked. The intervening fire fighters therefore carry out a chemical survey as soon as possible. A chemical survey is a set of activities leading to a detection, characterization, identification or even determination of hazardous chemicals. By the chemical survey various devices detecting the timely presence of the hazardous substances are used. The aim of the diploma thesis was the characterization and the subsequent test of the portable detection device GASTEC GV-100 in the analysis of an unknown hazardous substance. This simple detection device has many advantages, but some disadvantages as well. It is not very appropriate for using during intervention, maybe with another type of suction pump. It can be used for measuring gas and vapour concentrations in the transportation of petroleum products, in research laboratories and to prevent accidents in various types of operations.