The main type of heating equipment was to be reported even if it was temporarily out of order at the time of enumeration. For vacant units from which the heating equipment had been removed, the equipment used by the last occupants was to be reported.

Steam or hot water refers to a central heating system in which heat from steam or hot water is delivered through radiators or heating coils. Warm air furnace refers to a central system which provides warm air through ducts lending to the various rooms. Built-in room units are permanently installed heating units in floors, walls, or ceilings. They include Boor, wall, or pipeless furnaces as well as built-in electrical units. Floor, wall, and pipeless furnaces deliver warm air to immediately adjacent rooms but do not have ducts leading to other rooms. Other means-with flue describes stoves, radiant gas heaters, fireplaces, and the like connected to a chimney or flue which carries off the smoke or fumes. Other means-without flue describes portable or plug-in devices not connected to a chimney or Rue, such as electric heaters, electric steam radiators, kerosene heaters, and radiant gas heaters.