Description Morrison Brothers 748A-3200 AV Pressure vacuum vent designed for installation on top of thevent pipe of an aboveground or underground storage tank.Poppets seal vapors in the tank when pressure is equalized. Key Features Vents outward and upward in compliance with NFPA 30 Tri-polar mounting screws for mounting exhaust hood in any of three positions Optional dryer connections accommodate the installation of desiccant dryers on vacuum connection Optional pressure discharge hood facilitates piping pressure relief to desired discharge point