A data center has a room having a cold aisle and a hot aisle and a plurality of electronic components disposed between the cold and hot aisles. At least one air-to-liquid heat exchanger is disposed between the hot and cold aisles. At least one first fan circulates air in the room at a first flow rate. The at least one first fan circulates air through the at least one air-to-liquid heat exchanger from the hot aisle to the cold aisle. An air supply system is fluidly connected to the room. The air supply system includes an air filter, and a second fan supplying air from outside the room to the room at a second flow rate. The second flow rate is lower than the first flow rate. A data center cooling system and a data center having the data center cooling system are also disclosed.