The threshold limit values for chemical substances that are used or produced in workplaces are a valuable tool for the industrial hygienists, the safety engineers and generally for employers and employees. In the framework of the written safety assessment, the threshold limit values serve as reference values and correspond to concentrations that should not be exceeded for the specific substances in a workplace. Therefore they play a significant role in the prevention process. This publication of ELINYAE includes the threshold limit values that derive from the Greek legislation, and the related values of the American Conference of Governmental Industrial Hygienists (ACGIH) and of the German Research Foundation (DFG). In this way, the work of the professionals in the field of occupational health and safety is significantly facilitated.