Products belonging to TER's Atex series are suitable for hazardous, potentially explosive areas. Hazardous areas are places where, under certain conditions, explosive atmosphere may form. An explosive atmosphere is a mixture of air and gases, vapours, fumes or combustible dust, whose combustion spreads rapidly (explosion) after ignition at atmospheric pressure.

Users are responsible for carrying out a classification of hazardous areas, as set out in European Directive 1999/92/EC. International standards provide criteria for classification of hazardous areas depending on their chemical nature, physical characteristics and quantity of substances used, as well as on the frequency and length of time when an explosive mixture may occur.