A double membrane for a diaphragm pump for fluidizing, covering and conveying dusty products, such as, for example, pulverized coal, with the aid of an inert gas at pressures of up to 7 MPa, the diaphragm pump having a porous, curved loosening element made from aluminum, monitors and ensures the membrane tightness by designing the double membrane with an integrated pressure sensor for monitoring leakages. A hermetically tight separation between the hydraulic chamber and dust chamber of the diaphragm pump can therefore be ensured and damage to the membrane can be promptly identified. Complicated repair and cleaning measures of the entire dust system or hydraulic system in the event of membrane damage are prevented and the tightness of the membrane is maintained during the incident. Particular refinements relate to the composition of the individual membranes and the interaction thereof.