Knowledge about flame deflagrations in mixtures of methane and diluted coal dust assists in the prediction of fires and explosions, and in the design of adequate protective systems. This vital lack of information on the role of hybrid mixtures (methane/coal dust) is covered in this work by employing a novel Large Scale Straight Duct (LSSD) designed specifically for this purpose. The hybrid fuel was injected along the first 8 m of the 30 m long LSSD. The results revealed that a 30 g m(-3) coal dust concentration boosted the flame travel distance, from 6.5 m to 28.5 m, and increased the over pressure rise profile to 0.135 bar. The over pressure rise (OPR), pressure wave velocity, flame intensity and the flame velocity were significantly boosted along the LSSD in the presence of 10 g m(-3) or 30 g m(-3) coal dust concentrations in the methane flame deflagrations. Finally, the high speed camera showed that the presence of the coal dust enhanced the turbulence in the front flame. Consequently, the pressure wave and flame velocities were both increased when a 10 g m(-3) coal dust concentration coexisted with a 9.5% methane concentration in the deflagration. (C) 2017 Elsevier B.V. All rights reserved.