Dust explosion hazard exists in plants and facilities wherever combustible dusts are handled. The minimum ignition temperature of dust clouds is an important factor requiring special attention for the design of any explosion preventive measures. The present paper is confined to a study of the minimum ignition temperature of the cloud of polyethylene, an organic dust. This parameter was determined using the Godbert-Greenwald furnace apparatus for different particle sizes and dust concentrations. Some preliminary experiments were carried out for determination of minimum explosive concentrations of polyethylene dust to specify experimental conditions for determination of minimum ignition temperature. The experimental results, particularly variation of minimum ignition temperature with particle size and dust concentration, have been explained on the basis of a two-stage ignition involving devolatilization of solid particles into gaseous intermediates and homogeneous combustion of these gaseous components. A model was also developed for determining the minimum ignition temperature of polyethylene dust simulating conditions in the test furnace and this will be presented in a separate paper. * However, the application of existing data for designing appropriate preventive and mitigating measures to combat the hazard of industrial dust explosions is usually associated with inherent error due to difficulties encountered in simulation of process-plant conditions in laboratory-scale experiments. Thus either the data are to be produced for every situation and system or these will have to be estimated based on known correlations. These relationships are developed by a proper theoretical understanding of dust particle and dust cloud ignition leading to explosion. This will ultimately help in formulating a mathematical model to relate the dependency of process parameters on the factors characterizing explosions. It will then be possible to evaluate dust explosion risk and devise safety measures theoretically without referring to reported experimental data or carrying out new tests.