A passive valveless gas vent for a landfill includes a sub-surface gas collection manifold for collecting sub-surface gas from beneath a geomembrane. The collection manifold includes a plenum for receiving sub-surface gas, and the plenum defines an interior volume. A conduit is connected to and extends upwardly from the plenum, with the conduit communicating with the interior volume of the plenum and having an upper discharge end. The conduit is adapted and provided for extending through an aperture in the geomembrane for communicating sub-surface gas from within the interior volume of the plenum through the geomembrane. A hood is positioned adjacent an upper portion of the conduit and defines a discharge chamber therein into which gas from the discharge end of the conduit is discharged. The hood also has a discharge outlet for venting gas from within the discharge chamber to atmosphere.