An apparatus for controlling a flow of gas comprises a spiral path guiding member. The spiral path guiding member comprises at least two groups of guiding plates. Each guiding plate of each group is disposed in an axial direction to form a longitudinal axis. Each group is spaced apart in the longitudinal direction. A surface of each guiding plate is substantially parallel to the longitudinal axis. At least one guiding plate of each group has a guiding plate opening. Guiding plate openings of the guiding plates may facilitate gas to flow in a spiral flow path.