Abstract: A gas flow regulator for gases with condensable components, which delivers ases at constant pressure with constant average composition comprising a gas flow control mechanism, preferably including a spring-loaded membrane bounding a receiving chamber, which is subjected to the pressure of the gases flowing in and which an inlet valve control; and a cooling section connected and vertically oriented to the gas flow control mechanism by which the proportions of the condensable components are held at a partial pressure given by the cooling temperature, and a means for maintaining the gas flow control mechanism at a temperature above the condensation point. A restrictor, preferably an adjustable outlet valve, is connected after the cooling section to help maintain the membrane under pressure by the flowing gas, from which all condensate formed arrives in the region below the regulator directly by action of the force of gravity.