Statistical comparison of diesel particulate matter measurement methods.

Four methods are used to quantify diesel particulate matter (DPM) in the mine environment: respirable combustible dust sampling (RCD), size selective sampling with gravimetric analysis (SSG), respirable dust sampling with elemental carbon (EC) analysis, and respirable dust sampling with total carbon (TC) analysis. The authors assembled data from three underground mine studies to statistically compare these methods. The sampling protocol used in each study was similar. For all the four methods, samples were collected in triplicate at three locations-upwind and downwind of the diesel scoop and on the scoop. The methods were compared with respect to their precision, selectivity, sensitivity, and LOD, as well as their limitations in measuring DPM concentrations. This constitutes a meta-analysis of the available data and provides information over a broader range of mining conditions and DPM concentrations than any of the individual studies. The weighing imprecision for the SSG method is almost twice that for the RCD technique. The imprecision of the EC and TC methods are a function of the mass loading, and EC has a lower imprecision than TC. The EC method was used as the reference "gold standard" against which the other methods were evaluated. The RCD, SSG, and TC methods exhibited substantial levels of interference, leading to much higher minimum concentrations that can be measured by these methods. Of the three, the SSG method has the highest level of interference, primarily from nondiesel material that is collected in the <0.8 microm size range.