To prevent contamination from a syringe needle or a contaminated medical apparatus used in a hospital or the like.

In the radiation down-draft melting furnace, heat resistant bricks 3 are laid on a furnace bottom, and an exhaust groove 2 is provided on a brick upper part. The heat resistant bricks 3 are perpendicularly arranged like a grid on the exhaust groove, and a thermocouple 4 is attached above it. Right and left side walls and a ceiling part are formed by heat resistant bricks 5, a door 6 is formed by heat resistant bricks in a side part which is the front of the furnace, and a thermocouple is attached to an interior of the furnace and it is connected to a power source 7. By covering a whole inner side of the thermocouple by a refractory material 8, forming a hole or a gap in a bottom of the refractory material 8, and providing a convection groove for providing high temperature, melting and sterilization are carried out by radiation down-draft heat. By covering a whole outer side of the heat resistant bricks by a heat insulating material 11, and providing piping 9 for dissipating heat from the exhaust groove and a catalyst 10 for smoke reduction/cleaning, exhaust is detoxified.