A. The heat from the fire drives the gases from the coal and they are
ignited by the hot flame as they pass over the bright fire; the coke
which is left burns where it is.

28. Q. In what condition should the fire be to consume these gases?

A. A bright white coke fire, almost incandescent.

29. Q. What is the temperature of the fire when in this condition?

A. It must not be less than 1,800 degrees Fahrenheit to consume the
gases liberated from the coal, and it only requires from 750 to 900
degrees Fahrenheit to burn the coke that remains on the grate; as coke
burns from the outside, less heat is required to consume it.

30. Q. How can the fire be maintained in this condition?

A. By adding coal to the fire in small quantities, spreading it over the
grate surface and no faster than it is burned.

31. Q. What is black smoke? Is it combustible?

A. Black smoke consists of small particles of carbon suspended in the
gases of combustion and indicates incomplete combustion. Black smoke is
not combustible, it is like lampblack and cannot be burned after having
been produced. The production of it can be prevented by suitable
arrangements and manipulation.

32. Q. Should the gas not burn in the fire-box, will it burn after it
enters the flues? Why?