The dolomite inerting requirements of coal dust/air and methane/coal dust/air mixtures have been determined experimentally. All tests were conducted at initial pressures of nominally 1.0 bar in a 26-L spherical explosion bomb. Run-of-mine coal from the Prince, Lingan and Phalen seams of the Cape Breton Development Corporation was used. Two size fractions of each coal were tested at a single dust concentration of 0.5 kg/m3, with dolomite concentrations ranging from 20% (on a weight basis) of the total solids mixture to the percentage required to suppress an explosion. It was observed that methane admixture brings about an increase in the dolomite percentage and the total incombustible content needed for suppression. The additional dolomite required in the presence of methane was predicted reasonably well by an empirical relationship developed by the U.S. Bureau of Mines. Coal particle size and volatility were also found to strongly affect the inerting level, with more dolomite being required for finer or higher volatility coals. The results from this work show that there is no rationale for relaxing the current rock dusting regulations in Canada.