Disclosed is a venting device (300), including
a) a venting member (305) that is made from a hydrophobic and gas-permeable material, the venting member (305 )having an environment coupling surface and an opposed cartridge coupling surface,
b) a carrier member (315), the carrier member (315) structurally supporting the venting member (305).
The venting member is designed such that the venting device (300) and a liquid drug cartridge (100) form, in the assembled state, a compact common cartridge assembly. After inserting the cartridge assembly into a cartridge compartment of an ambulatory infusion device, the cartridge coupling surface fluidic couples, to a non liquid contacting outer surface of the movable wall, and the environment coupling surface at the same time fluidic couples to the environment.