For the 1996-1998 American Community Survey, the data on air conditioning were obtained from questionnaire item H14 for both occupied and vacant housing units.
Air conditioning is defined as the cooling of air by a refrigeration unit or a heat pump.
It does not include evaporative coolers or fans. A central system cools several rooms in the housing unit. In an apartment building, a central system may cool all apartments in the structure or there may be several systems, each cooling one or more apartments. A room unit is an individual air conditioner generally installed in a window or wall, and cools only one room. The question was dropped in the 1999 American Community Survey.