How does one select an air conditioner?

An air conditioning system, or a stand-alone air conditioner, provides heating, cooling, ventilation, and humidity control for all or part of a building. 'Central', 'all-air' air conditioning systems are often installed in modern residences, offices, and public buildings, but are difficult to retrofit (install in a building that was not designed to receive it) because of the bulky air ducts required. A duct system must be carefully maintained to prevent the growth of pathogenic bacteria in the ducts. An alternative to large ducts to carry the needed air to heat or cool an area is the use of remote fan coils or split systems. These systems, although most often seen in residential applications, are gaining popularity in small commercial buildings. The remote coil is connected to a remote condenser unit using piping instead of ducts.