A surface supplied diver can provide breathing gas from their pneumofathometer hose, which can be inserted under the neck seal of the helmet and turned on at the gas panel to provide an adequate but noisy free-flow supply. This is normally sufficient to ventilate the casualty for the return to the surface or bell. In some cases it may be necessary to disconnect the casualty from their umbilical, if it is irretrievably trapped. This requires a few minutes work with spanners, and will lose any voice communications that may have remained. It is possible to connect a replacement umbilical if one is available. This is not usually the case from a bell, as the umbilicals occupy too much space to carry a spare.