Systems are provided for cooling data centers based on a cooperative system including a plurality of Indirect Air-Side Economizers, also referred to as Recirculation Air Cooling Units, that are advantageously operated in conjunction with one or more Side Stream Filtration Units or filters inclusive to a portion of the IASE/RACUs, and one or more Make-Up Air Dehumidification/Humidification Units for the introduction of ventilation air and control of humidity within the enclosed space. An objective of the systems according to this disclosure is to provide the necessary rejection of heat, removal of particulate from the air, and control of the absolute moisture content of the air within a data center.