An infusion device for infusion of a fluid from a reservoir into a body, the infusion device being connectable to an infusion set adaptor at a connecting site, the infusion device comprising: a drive mechanism to operatively couple with at least a portion of the reservoir； a housing being sized to contain at least a portion of the reservoir, wherein the drive mechanism is at least partially or fully contained within the housing； a sealing device that permits the passage of air into and out of the housing or a housing compartment and inhibits the passage of liquids into the housing or a housing compartment through the sealing device； wherein the sealing device is arranged at the drive mechanism or at a location between a part of the drive mechanism and the connecting site of the infusion set adaptor or at the connecting site of the infusion set adaptor.
