The minimum temperature at which dust layers or deposits ignite is considered to be very important in industries where smoldering fires could occur. Experiments were conducted on the self-ignition behavior of magnesium powder layers. The estimated effective thermal conductivity k for modeling is 0.17 W m(-1) K-1. The minimum ignition temperature (MIT) of magnesium powder layers for four different particle sizes: 6, 47, 104 and 173 p,m, are also determined in these experiments. A model was developed describing temperature distribution and its change over time while considering the melting and boiling of magnesium powder. Parameter analysis shown that increasing particle size from 6 to 173 mu m increased MIT from 710 to 760 K, and increased thickness of the dust layer led to a decreased MIT. The calculation termination time more than 5000s didn't significantly impact MIT. Comparing predicted and experimental data showed satisfactory agreement for MIT of magnesium powder layers at various particle sizes. According to the ignition process of magnesium powder layer, a meaningful definition for the most sensitive ignition position (MSIP) was proposed and should be taken into consideration when preventing smoldering fires induced by hot plates. (c) 2012 Elsevier B.V. All rights reserved.