The industrial hygiene and safety aspects with internal combustion engines in mining systems is truly interdisciplinary and encompasses many fields such as mine ventilation, exhaust gas and particulate analyses, mine atmospheric environment monitoring, mathematical modeling of generation, dilution and dispersion of pollutants in ventilation systems, and engine testing and approval. Mathematical models of the dilution and dispersion of diesel exhaust contaminants can be useful only if these models can be validated. In this report, experiments that were specially designed for these purposes are described. These experiments were conducted in the Bureau of Mines safety research coal mine in Bruceton, Pennsylvania, On the basis of this study, the data collected, and further review of available literature, it is concluded that mathematical models of dilution and dispersion are useful tools for mine ventilation planning. Additional objectives of this study about which conclusions and recommendations are reported include (1) evaluation of mine atmosphere contaminant monitoring systems, (2) optimum sampling site locations, (3) model sensitivity and error analyses, (4) computer coding of mathematical models, and (5) development of a diesel bibliography.