The most common operations in food industries where grains are handled, thus producing combustible dusts, are grinding, drying, transport in bucket elevators and conveyors, pneumatic transport, filtering, and storage in silos. Unfortunately, these operations all too often give rise to fires or explosions with catastrophic consequences. Spontaneous combustion must be considered to be a potential ignition source for a dust or gas explosion every time a large mass of combustible dust comes in contact with air. In this paper we present a methodological approach to the characterization of combustible products (grains, pellets, dusts, etc) with respect to self-heating and fermentation and give results for certain agricultural dusts. Our method includes the use of modeling and various laboratory tests such as Thermal Differential Analysis coupled with Thermo-Gravimetric Analysis (DTA-TGA), Isothermal Oven Tests (at ambient pressure and elevated pressure), and Adiabatic Calorimetry. The objective of these tests is not only to rank the various products by order of reactivity but to determine under which conditions a given product will pose a threat of spontaneous combustion.