Active volcanism observed on Io could provide a continuous source of gases from Io's interior. Only a small fraction of what is coming out of Io's volcanoes is escaping; the bulk of it is being recycled. There must be an atmospheric reservoir which maintains the gases until they have had a chance to recycle. Such an atmosphere must be protected from Jupiter's corotating plasma in order to be stable. Only the dayside atmosphere is subject to escape, while the cold nightside and poles would serve as a sink for atmospheric gases. However, the scavenging of atmospheric gases is maximum at the eastern elongation and minimum at the western elongation. A stable SO2 atmosphere on Io shows promise if the volcanic activity is continuous. If the volcanoes stop erupting, the atmosphere will be depleted.