Figure 1. A schematic diagram of a Narkomed anesthesia machine. Possible pathways taken by fresh gas to exit the anesthesia machine are shown. See text for further details. If the negative pressure relief valve of the scavenger malfunctions so that atmospheric pressure holds the inspiratory valve closed, the fresh gas flow may preferentially be directed through the carbon dioxide absorbent with the potential for absorbent dehydration even if the reservoir bag is in place.