| This thesis evaluates the effectiveness of crankcase ventilators and diesel oxidation catalysts on the in-cabin air quality in a diesel engine school bus. Three diesel powered school buses from Pueblo West School District 70 were selected for study. The in-cabin air quality for these buses was monitored using filter sampling techniques to measure PM 2.5, elemental carbon, and organic carbon, and cartridge sampling for carbonyls including formaldehyde, acetaldehyde, and acetone. Continuous measurements of particle number and carbon monoxide were made simultaneously with velocity. Measurements were taken on each bus three times, for a total of 9 pre-retrofit runs. The buses were retrofitted with Racor 4500 closed crankcase ventilation units and Donaldson Series 6100 diesel oxidation catalysts (DOC) and the measurements were repeated to yield 9 post-retrofit runs.;Results include decreases in levels of particle number concentration, PM 2.5, EC, OC, and formaldehyde after control devices were installed. Mean in-cabin PM 2.5 concentrations were about 56% lower, number concentrations 33 to 41% lower, OC concentrations 41% lower, EC concentrations 85% lower, and formaldehyde concentrations 32% lower after control devices were installed. Reductions for number concentration, OC, and formaldehyde were statistically significant. Reductions for PM 2.5 were not statistically significant, due to the limited number of samples and high degree of variability. No correlation was detected between velocity and particle count.;While the results of this study indicate that the retrofits are effective in reducing in-cabin air pollution, the results are variable among runs. Ranges for air pollutants measured in this study agree with ranges seen in similar studies, yet variability is high among studies. The studies show that retrofit technologies do improve in-cabin air quality, but more technology needs to be developed to capture further reductions. |
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