Embodiments of the invention provide a barrier for protecting hearing aid metal-air battery assemblies from exposure to liquids causing obstruction of a battery air vent. One embodiment provides a barrier configured to be attached to a CIC hearing aid battery having a vent. The barrier has an oxygen permeability configured to allow the diffusion of sufficient oxygen for a battery to meet the power demands of a hearing aid operating in the bony portion of the ear canal over an extended time period. The barrier has a physical property configured to substantially prevent liquid obstruction of at least a portion of the vent on a metal-air battery such as a zinc-air battery. The physical property can be at least one of a hydrophobicity, oleophobocity or surface energy. The barrier can be directly attached to the battery or indirectly via a holder and can encase substantially the entire battery.