A thermal device that contains an exothermic composition is provided. The exothermic composition includes a metal that is capable of undergoing an oxidation reaction in the presence of moisture and oxygen to generate heat. Certain aspects of the thermal device may be optimized to supply a controlled amount of moisture and/or oxygen to the exothermic composition during use. Through selective control over the supply of these reactants, a heating profile may be achieved in which an elevated temperature is reached quickly and maintained over an extended period of time.
