Mining Publication: The Effects of Passive Diesel Particulate Filters on Diesel Particulate Matter Concentrations in Two Underground Metal/Nonmetal Mines

• Diesel particulate filters
• Diesel particulate matter
• Nitrogen dioxide

In 2008, the final rule limiting the personal exposure of underground metal/non-metal miners to diesel particulate matter (DPM) went into effect. In response, metal/non-metal mines are implementing a variety of control technologies to comply with this rule. Two mines have implemented a control strategy where a majority of their larger vehicles, which emit most of the particulate, were retrofitted with passive diesel particulate filters (DPFs). In addition to the DPFs, one mine increased ventilation to dilute the DPM concentrations. A second mine used a combination of DPFs, biodiesel fuel, flow-through particulate filters, ventilation, and enclosed cabs to limit the exposure to DPM to miners. In this study, NIOSH measured the atmospheric concentrations of DPM and gases in these two mines in order to evaluate the effects of the control strategies on the atmospheric DPM concentrations. The results showed that the DPFs substantially reduced the particulate emissions, and in general, the DPM concentrations were below the final limit. However, the DPM concentrations were occasionally over the final limit in areas where vehicles without DPFs were operating and in some areas with lower ventilation rates. These findings indicate that in a few areas of the mine, additional controls such as increased ventilation may be needed to reduce the DPM concentrations below the final limit. NIOSH was also interested in the atmospheric nitrogen dioxide (NO₂) concentrations in these mines, since some passive DPFs can increase NO₂ concentrations. The measured NO₂ concentrations did not exceed 5 part per million (ppm) (ACGIH STEL) at these mines.