E. Off-board O2 and/or Bailout Deco Tank

MX Rebreather - Off-board O2 and/or Bailout Deco Tank

A source of Oxygen is needed to compensate for any deficiencies in the loop PPO2. As O2 usage during a normal dive is minimal and because O2 can not be used as a deep bailout, it should be carried in an offboard supply configuration.  Generally the offboard cylinders should be as neutral as possible and as small as possible, to both reduce drag and help facilitate a balanced rig. Again this is core to the principles to UTD/DIR configuration. Carrying O2 on your back (and the diluent/bailout gas offboard ) does not makes sense from a simple volume of bailout/dil needed basis. Keep in mind you will need the bailout/diluent volume during emergencies and you don’t need the volume of O2. Your metabolism is small and does not change with depth, however your volumetric needs of diluent/bailout change dramatically with depth changes and multiple level exploration diving, not mention the massive increase in OC consumption rates when deep or in an emergency.

Carrying the bailout/diluent on your back accommodates the ability to carry large volumes of gas without affecting balance or having to carry multiple “bailout” stages. In the MX300 configuration, we can carry almost 300cft / 9000l of bailout/diluent on our back tanks. It is quite comfortable and very well balanced in the water and is consistent with ALL other UTD/DIR configurations of OC/pSCR/MX90 and so on. If we were to try to move the bailout/diluent to offboard, we would need almost 4 * AL80’s/11l tanks. Not so easy to manage and not well balanced. As far as O2, a AL 40cft/6l offboard bottle of O2 is small, streamlined, easy to manage, balanced, already part of the UTD/DIR configuration, and can provide almost 1700 minutes of rebreather time, regardless of depth and based on a standard 0.7l/min metabolic rate. That’s 28 hours of O2, well past the CO2 scrubber abilities.

In standard UTD/DIR our bailout system or configuration already includes an off-board bailout O2 deco bottle for OC bailout deco. Additional OC bailout deco tanks can be added, such as Nitrox 50,, if we are going deeper or have longer bottom times and need more bailout OC decompression gas volume.

In normal rebreather operations, we simply tap into that O2 deco cylinder and supply what little O2 we need to run the MXRB. If we are not in need of any bailout OC deco, such as in recreational NDL diving, then we can simply attach a small 6cft/1L bottle of O2 to our left side, replacing the drysuit inflation or argon bottle. This bottle will give you 250 mins of O2 (based on 0.7l per minute metabolism,) more time than NDL allows. Keep in mind that in UTD/DIR NDL diving is considered at depths shallower than 100’/30m and therefore no Helium is needed in the diluent/bailout, so your drysuit can be inflated from the back mounted dil cylinders, again from the left post, like in standard UTD/DIR OC configuration.