The U.S. Bureau of Mines has been conducting research on the secondary explosion hazards associated with the mining of oil shale under gassy mine conditions. Explosive incendivity tests have been conducted in a 28-m3 (1,000-ft3) gallery to evaluate the relative incendivity of experimental emulsion-anfo blends. The incendivity was measured by determining the minimum inert stemming requirements for preventing the ignition of a methane-air atmosphere by the discharge of hot detonation products from a 5.7-Cm (2.25-In) diameter borehole. The relative incendivities of several blasting agents using ammonium nitrate, calcium nitrate, and sodium nitrate and with various oxygen balances were determined and compared with anfo. Results indicate the less incendive blasting agents are generally more oxygen balanced, contain sodium or calcium nitrates, and tend to generate less hydrogen and carbon monoxide. These excess fuels appear to burn outside the borehole, thereby contributing to the methane ignition process. Results indicate that there is merit in tailoring an explosive's composition to reduce the probability of igniting the methane released during normal oil shale blasting operations. The proper selection of explosives and stemming materials should significantly reduce the probability of gas explosions under gassy oil shale mining conditions.