A ventilator for exhausting gas from an exhaust port, by utilizing wind or relative wind around and through the ventilator to create a reduced pressure zone at an open exhaust port. Tapered intermediate portions extend from the opposite ends of a centrally located throat portion within a body of the ventilator to a pair of opposite mouths through which gas can flow out through the ventilator from the exhaust port. Each mouth of the ventilator has an opening with an area significantly larger than the area of a flow path within the throat portion. The throat portion may be of constant internal cross-sectional area over its entire length.