The equipment used for heating ambient air in the housing unit, such as: central warm-air furnace, heat pump, built-in electric units, steam or hot-water system, floor, wall, or pipeless furnace, heating stove, room heater, fireplace, or portable heater. The main space-heating equipment is reported as such even if it is temporarily out of order. A "cooking stove" may be used as the mainspace-heating equipment even though it was built for preparing food. (See descriptions of specific types of space-heating equipment: Central Warm-Air Furnace; Heat Pump [Reverse-Cycle System]; Built-In Electric Units; Steam or Hot-Water System; Floor, Wall, or Pipeless Furnace; Heating Stove Burning Wood, Coal, or Coke; and Room Heater Burning Gas, Oil, or Kerosene.)