A device includes a housing having a hollow center and a case having a hollow fiber membrane. The case is at least partially located inside the hollow center of the housing. A first gas flow flows to the hollow center through an introducing pipe and exits the housing via a discharging pipe. A second gas flow flows through the hollow fiber membrane in the case. The first gas flow enters the case through an inflow opening in the case from a gap between a wall of the housing and the case and exits the case through a discharging opening in the case to the gap between the wall of the housing and the case. The introducing pipe is located adjacent to a dividing wall. The device provides a humidifying property by transferring moisture from the first gas flow to the second gas flow or vice versa.