Warm Air Radiant Heat The balance of the radiant heat is reflected from the heating surface to be absorbed by surrounding cool surfaces. A part of the secondary ray energy, now of longer wave length, is absorbed by moisture and particles in the air, which helps to raise the temperature. As a secondary effect, the room temperature is raised by convective transfer from the heated surface. Infra-red rays travel in divergent straight lines from heat source to all surfaces and objects without heating

Each opening must have a minimum free area of at least 1 square inch per 1000 BTU per hour of total input rating of all appliances within the space but not less than 100 square inches. If the furnace is installed in a space within a building of tight construction and air must be supplied from outdoors. In this case, one opening shall be within 12" of the ceiling and the other within 12" of the floor. If vertical combustion ducts are run, each opening must have a free area of at least 1 square in