The air conditioning system of data centers is one of the essential infrastructures for the operation of information technology equipment (ITE): the processing and storage devices generate heat (up to several kW per square meter of plant) that must be disposed of to keep the temperature within values which ensure optimum operating conditions. Humidity also must be controlled, since values too low increase the probability for electrostatic discharge, while excessive values accelerate any corrosion process and affect the performance of some devices. There are various types of data centers that differ both in size and in tne configuration of the air conditioning system. The most traditional ones are the systems with the servers positioned at the center of the environment and conditioning units arranged along the perimeter (CCU or CRAC) while for the air flow, the floor and ceiling are exploited come plenum. In layouts with hot/cold aisle the servers are arranged so as to create two separate areas, with air conditioning units (in row cooling installed directly next to the ITE) that suck the exhaust air from the hot aisle servers and enter it cooled in the cold aisle. The air conditioning systems can be with direct expansion, with external condensing units, or water cooled, with remote chiller. We also see more and more data centers that fully exploit the potential of the freecooling, possibly upgraded with direct (DEC) or indirect (IEC) evaporative cooling systems. Lately we are witnessing the development of modular data centers provided with containers that include all the necessary infrastructure: ITE, UPS, "mechanic" air conditioning systems, freecooling with DEC and/or IEC. . In this field, where continuity of operation (Mission Critical) is essential, the ongoing technological development and research on energy savings are reflected in a constant evolution of air conditioning solutions. Thanks to its 40 years of experience in this field and to the continuous research, Carel provides integrated solutions for temperature and humidity control, based on an extensive offer of innovative, reliable and energy saving products: programmable electronic controls, sensors, humidifiers, evaporative coolers, electronic expansion valves, BLDC inverters and monitoring systems.