SRD:Bottle of Air
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Bottle of Air: This item appears to be a normal glass bottle with a cork. When taken to any airless environment it retains air within it at all times, continually renewing its contents. This means that a character can draw air out of the bottle to breathe. The bottle can even be shared by multiple characters who pass it around. Breathing out of the bottle is a standard action, but a character so doing can then act for as long as she can hold her breath.