Dust explosions, especially a fine particle explosion, are hazards with severe consequences, which have caused significant loss of life and property damage in several process industries. Minimum explosive concentration (MEC) is one of the important parameters used to evaluate the dust combustion and explosion risks of a dust and helps design corresponding safeguards in industry. Although there has been a tremendous boost in the application of nanomaterials in the past two decades, the efforts to evaluate the safety boundaries of nanomaterials are not sufficient; e.g., the experimental evaluation of their MECs is very scarce. To fill this gap, MEC tests of several commercially available carbon nanofibers were conducted in this study by following ASTM standards. The results obtained demonstrate that a reduction in particle size by a mechanical-milling process could decrease MEC while an annealing process (1500 or 3000 degrees C) could increase MEC and, thus, lower the explosion risk. Agglomeration, particle size, and existence of nanosized iron particles all contribute to changes in the MEC, which were not disclosed in previous studies for MEC estimation. To describe the effect of these factors more accurately, a heterogeneous model based on a dynamic perspective is proposed to evaluate the influences of those factors on the heat transfer process and ultimately the explosibility of nanomaterials. Detailed analyses of the mechanisms affecting the combustion and explosion process were also performed in this study.