An embodiment includes a first space, a second space, a first damper, a second damper, and a third damper. The first space is connected to a cold space, having cold air reside therein to send to the cold space. The second space has return air reside therein, as it is discharged from a hot space. The first damper has an opening adjusted under control of a controller to take in outdoor air to the first space, and is operable to have an open state in an emergency with a server being supplied with power. The second damper has an opening adjusted under control of the controller to discharge return air in the second space, outside thereof, and is operable to have an open state in the emergency. The third damper has an opening adjusted under control of the controller to recirculate return air in the second space to the first space.