Described is drug infusion device with one or more vents that permit the passage of gas between the exterior and interior of the devices housing. In one embodiment the device may include multiple interior chambers of differing volume and pressure sensors placed between them, while vents to ambient pressure are included in each chamber. According to this exemplary structure, the readings from the pressure sensor may be used to determine malfunctions in the venting of the device and/or changes in pressure that could cause the unintended delivery of medication.
