As a useful method of preventing dust explosions, nitrogen (N-2), an incombustible gas, has been applied to an explosive atmosphere. This paper is a report that quantitatively determines whether the minimum ignition energy of powder depends on the nitrogen (or oxygen) concentration in the air. Hartman vertical-tube apparatus and six sample powders were used in this study. The results show that the minimum ignition energies of all of the powders used in this study increased with increased amounts of N-2 in the air. However, the effects were different in all of the sample powders. We finally suggest that the N-2 concentration of 84% (or above) prevents dust explosions due to electrostatic discharges in the industrial process with the sample powders used in this experiment. (C) 2015 Elsevier Ltd. All rights reserved.