If this item is present in your quick-use inventory then whenever your breath bar goes below 5 it will automatically make use of any air tanks that are present in your quick-use inventory to replenish your breath supply. Note that it will not use air tanks that are present elsewhere in your inventory, only ones in your quick-use bar.=
If you're underwater and you're running out of breath, wield this item and use it to replenish 5 bubbles on your breath bar. When fully charged this tank has @1 uses before it becomes empty.=
Place this machine somewhere that it has access to air (one of its adjacent nodes needs to have air in it). When you click on it with an empty or partly-empty compressed air tank the tank will be refilled.=