A delivery system configured to be secured on a patient skin which comprises a first container having a first movable wall and a first storage compartment intended to store a medical fluid； a second container having a second movable wall and a second storage compartment； and a skin adherable unit configured to secure the first container and the second container to the patient skin. The first movable wall and the second movable wall are facing each other and define a containers' interface having a cavity. The system further comprises a vent device configured to allow a pressure equilibration between the cavity of the containers' interface and the outside of the delivery system when at least one of the first movable wall and the second movable wall moves.
