Diesel particulate matter (DPM) continues to be scrutinized as an adverse occupational exposure agent. Currently, the air sampling protocol approved by the U.S. Mine Safety and Health Administration (MSHA) to quantify exposure to DPM in mines designates an SKC impactor as the sample collection device and limits exposure to the total carbon faction of a DPM aerosol. Because use of this impactor requires submission of the sample to an analytical laboratory, it inherently includes a lag time before workplace exposures can be determined. Thus, mine operators who use this MSHA-approved sampling device to monitor personal DPM exposures are faced with the possibility of realizing unacceptable airborne concentrations after the exposures have occurred.