Combustion
In parts of the country where the temperature goes below 60° F. it becomes necessary to provide artificial heat to warm houses in order that health may be maintained at the least possible expenditure of energy. The most common method of producing heat for heating purposes is by combustion. Its obedience to certain physical laws is infallible. Heat is liberated from such material as coal and wood by combustion and is the result of the chemical action of this combustion; it is then transmitted to the rooms to be heated either by air, water, or steam unless the combustion takes place in the room to be heated; then it is distributed throughout the room by radiation from the open fire or conduction from above.