Abstract: In a compensating membrane carburetor having a fuel accumulating chamber connected through idling and high-speed jets to a Venturi, a compensating chamber is provided which is maintained, naturally or artificially, at atmospheric pressure. A second chamber seals the external face of the compensating membrane from the environment of the carburetor and a first relief line, partially disposed in the carburetor, provides fluid communication between the compensating chamber and the second chamber to maintain the second chamber at atmospheric pressure. A second relief line is disposed substantially outside of the carburetor and also provides fluid communication between the compensating chamber and the second chamber, in order to insure the proper operation of the carburetor in the event of a blockage in one of the two lines.