Below is a list of Air Conditioning Units manufacturers from Frederick, Maryland. Air conditioning units remove heat from the air through the use of a compressor, a condenser, an expansion valve, a thermostat and a series of motorized fans. Some units may be connected to air ducts or air handling equipment. Contrary to a widespread idea, air conditioning units do not add cold air to a space but instead removes heat from the existing air, making the space feel cooler.