The occupational exposure limit value, or OELV in short, describes the average concentration of a substance in the air for which no acute or chronic adverse effects on the health of employees are to be expected during an average working time over a given reference period. The occupational exposure limit value is defined and used in the Ordinance on Hazardous Substances (GefStoffV). A list of occupational exposure limit values is provided in the Technical Rules for Hazardous Substances (TRGS) 900. Sources: Ordinance on Hazardous Substances; TRGS 900