12 to the latter the additional force exerted on the control membrane against the closure direction is determined using the relationship f dp a wh with dp being the pressure difference due to the pressure reducing elements pressure drop at the pressure reducing elements and a wh being the effective area of the first auxiliary membrane compared to the state of the art the first auxiliary membrane 14 thus compensates the pressure drop at the pressure reducing element and the control membrane therefore can be controlled in such a way that by use of the valve according to the invention an unacceptably high crankcase pressure can be avoided the load deflection lines shown in fig4 c are characteristic for the pressure course of a valve according to the further embodiments of the invention as they are shown in fig2 a to 2 c these valves compared to the one of fig1 are characterized by an additional second auxiliary membrane 17 the influence of the second auxiliary membrane is depicted schematically in fig4 c the second auxiliary membrane is charged on one of its sides by the reference pressure which corresponds to the atmospheric pressure or a pressure related to it and on its second side by the pressure at the outlet.