Research has shown that in coal mines utilizing diesel-powered equipment, the diesel exhaust particles are primarily smaller than 0.8 (μm in size, while the mine dust particles are larger than 0.8 μm. Formerly, three-stage personal samplers have been designed for separating the diesel exhaust from the mine dust particles by dividing the respirable particles at a particle size of 0.8 fim. Conventional impac-tors or cyclones were used to obtain the 0.8-ju.m cut point and to collect the mine dust particles on an impaction plate substrate or in a foil cup, and the diesel exhaust particles on a filter. However, these samplers had potential problems with particle overloading on the substrates and particles not being collected in conventional filter cassettes. A diesel exhaust/mine dust virtual impactor personal aerosol sampler (VIPAS) has been developed for use in diesel-powered underground coal mines that addresses the shortcomings of the previously designed samplers. The VIPAS consists of the 10-mm cyclone to remove the large, nonrespirable particles, followed by a O.S-μm cut point virtual impactor and two filter cassettes to divide and collect the two particle size fractions: the respirable coal dust and the respirable diesel particles.