Initial exposure monitoring is mandatory to ensure that all potentially exposed persons are not exposed to levels of DCM above the EPA limits. Users shall request HSRM to perform exposure monitoring before commencing any new operation involving DCM or altering existing operations in any manner that may lead to increased exposure. The results will be used to modify work practices or introduce engineering controls to ensure DCM exposure is within EPA standards. All improvements will be documented in the lab specific DCM SOP (See below). 

Two conditions may exempt an employer from conducting initial monitoring for DCM. 

1. If objective data generated during the last 5 years demonstrates DCM is not released in the workplace environment at or above the ECEL action level and EPA STEL and with initial monitoring conducted within 5 years of that data. 
2. If exposure to DCM is less than 30 days per year with two conditions: 
   1. Direct reading measurements must be taken in the environment to ensure levels are below the ECEL action level and EPA STEL.
   2. Appropriate controls must be put in place to ensure levels are below the ECEL and EPA STEL.

Exposure monitoring shall be conducted for all potentially exposed persons or for an individual or group of individuals determined to be representative of the exposure group. Monitoring must be taken when and where operating conditions are best representative of each potentially exposed person’s highest likely full shift, and 15-minute exposures occur.