This is a form of close control air conditioning where the indoor unit is installed such that the cold air is released in isles. The cold air is usually released from below the floor through perforated floor panels. The racks are usually arranged such that they face each other and come with fans for sucking the cold air from the cold isle before releasing them to the hot isle.

The hot isles are usually fitted with grilles, at the roof or close to the roof, that suck the hot air and return it back to the evaporator for cooling. Some evaporators come complete with humidifiers/dehumidifiers.