A pneumatically actuated vent valve for venting the headspace of a fuel storage tank such as generally cylindrical a gasoline delivery truck includes a housing, sealingly mounted in the top of the tank and having a central passage opening at its lower end into the headspace of the tank and opening at its upper end, at the anterior of the tank into a hood. A pneumatic motor cylinder defining a piston chamber closed at its upper end is integrally formed with the housing coaxial to the central passage and a piston rod projecting downwardly from the piston chamber carries a valve head at its lower end disposed below the lower end of the housing. The valve head is normally biased upwardly into sealed engagement with a valve seal at the lower end of the central passage by three (or more) springs biased guide rods symmetrically disposed about the central passage wall. The valve is opened by supplying air under pressure to the upper end of the piston chamber via a flow passage through a web integrally joining the motor cylinder to the housing.
