Abstract: To provide a novel water-addition type, chemical exothermic agent. An exothermic agent comprising, per mass thereof, more than 30% but not more than 40% of a calcium oxide powder having an average particle size of 75 ?m to 150 ?m, and not less than 60% but less than 70% of a mixed aluminum powder in which an aluminum powder having such a particle size distribution that a particle size of 45 ?m pass is 70.0 to 80.0% and a particle size of 45 to 75 ?m is 20.0 to 30.0% and an aluminum powder having such a particle size distribution that a particle size of 45 ?m pass is 60 to 70%, a particle size of 45 ?m is 20 to 30%, a particle size of 63 ?m is 7 to 10% and a particle size of 75 ?m is 1.0 to 2.0% are mixed at a mass ratio of 1:2. This exothermic agent may further contain 5 to 10%, relative to its total mass, of at least one inorganic salt compound selected from the group consisting of calcium sulfate, ferrous sulfate, magnesium chloride, sodium sulfite, sodium phosphate, and sodium carbonate.

Abstract: To provide a novel water-addition type, chemical exothermic agent. An exothermic agent comprising, per mass thereof, more than 30% but not more than 40% of a calcium oxide powder having an average particle size of 75 ?m to 150 ?m, and not less than 60% but less than 70% of a mixed aluminum powder in which an aluminum powder having such a particle size distribution that a particle size of 45 ?m pass is 70.0 to 80.0% and a particle size of 45 to 75 ?m is 20.0 to 30.0% and an aluminum powder having such a particle size distribution that a particle size of 45 ?m pass is 60 to 70%, a particle size of 45 ?m is 20 to 30%, a particle size of 63 ?m is 7 to 10% and a particle size of 75 ?m is 1.0 to 2.0% are mixed at a mass ratio of 1:2. This exothermic agent may further contain 5 to 10%, relative to its total mass, of at least one inorganic salt compound selected from the group consisting of calcium sulfate, ferrous sulfate, magnesium chloride, sodium sulfite, sodium phosphate, and sodium carbonate.