Sampling and Interferences For Diesel Particulate Matter in Underground Metal and Nonmetal Mines

The United States Mine Safety and Health Administration, has proposed an exposure standard for diesel particulate matter for underground metal and nonmetal mining operations. These limits are in terms of total carbon as determined by the National Institute of Occupational Safety and Health (NIOSH) Method 5040. Method 5040 is a thermal optical procedure for determining elemental and organic carbon content of an airborne sample. Elemental and organic carbon content of the sample are added to obtain the total carbon concentration. Mining industry comments and concerns on the proposed regulation included: the applicability of Method 5040 to diesel particulate measurements, the sample collection system and the impact various interferences may have on diesel particulate measurements. Concerns on Method 5040 included accuracy, calibration of the instrumentation and calculation of the total carbon concentration. Sample collection issues addressed sample collection method (total dust (open face), respirable dust or submicron particulate). Potential interferences included: sample blanks, carbonaceous minerals (including carbonates), graphitic minerals, oil mist and cigarette smoke. In order to address these concerns, MSHA reviewed the analytical method, and conducted studies to verify the magnitude of the interferences. The sampling and analytical procedures and the results of the supporting tests are described in this paper