Standards of Permissible Exposure Limits at Job Site Article 9

In the case of exposure to two or more hazardous substances in the air of a job site, where their combined effects on health are neither synergistic nor independent, such effects shall be deemed additive, and the combined exposure shall be computed as follows:Em=(C1/L1)+(C2/L2)+-----(Cn/Ln)Where:Em is the equivalent exposure for the mixture of hazardous substances in air.Ci is the concentration of a particular substance i.Li is the permissible exposure limit given for that particular substance i.Once the sum (Em) exceeds unity (1), the exposure shall be considered to have been exceeded.