This paper describes a U.S. Bureau of Mines investigation of large-scale coal dust explosions in an experimental mine using a high speed clectropneumatic mechanism for the rapid grab-sampling of gases and dusts. This technique enables themonitoring of pyrolysis and charring in fuel dust particles, and the collection of gaseous combustion products, in both large and small-scale explosions. Data obtained from full-scale dust explosion tests at the Bureau of Mines Lake Lynn Test facility show the following: Rapid sampling appears to “freeze” the burned gas compositions at the flame temperature values.Gas samples taken entirely in the flame zone consist of pyrolysis and combustion products with very low residual oxygen.The particles collected in the flame zone show signs of extensive pyrolysis and charring. Measurements of gas concentrations and particle flame temperatures suggest that char burning may have occurred in the flame zone.