Abstract: A system and a method are provided for controlling flow of air and preventing flow of liquid within vent lines connected to, for example, a pipe line or other like piping systems. A housing is provided with a float and a seat within the housing having an opening therethrough wherein the float is capable of sealing the opening of the seat during a flooding condition. The first housing with the float is connected to one end of a vent line. A second housing is connected to another end of the vent line having a float therein for sealing an outlet formed by a seat with an opening therethrough. Optionally, a screen may be provided to prevent articles from entering the housing upon a flooding condition exposing the housing to both liquid and extraneous particles.