The underground mining industry recognizes that diesel-powered equipment has advantages over its electric counterparts such as greater mobility, flexibility, and high-power density, which may increase productivity. However, there is a potential health risk for miners exposed to diesel exhaust. The U.S. Bureau of Mines collaborated with Donaldson Company, Inc., to develop a disposable diesel exhaust filter (ddef) to remove soot from diesel exhaust. The principal application of the ddef is on permissible diesel- powered haulage vehicles used in coal mines. In-mine tests show that the filter reduces diesel exhaust aerosol levels in the mine environment by up to 95 pct. The usable life of the filter is from 10 to 36 h, depending on the altitude, engine, and duty cycle of the vehicle.