Emergency HBOT for decompression illness follows treatment schedules laid out in treatment tables. Most cases employ a recompression to absolute, the equivalent of of water, for 4.5 to 5.5 hours with the casualty breathing pure oxygen, but taking air breaks every 20 minutes to reduce oxygen toxicity. For extremely serious cases resulting from very deep dives, the treatment may require a chamber capable of a maximum pressure of , the equivalent of of water, and the ability to supply heliox as a breathing gas.