The Mk 5P


These pages contain information about the MK 5 Rebreather from Cis-Lunar. Many thanks to Steve Millard, of the University of Liverpool, for the information and pictures.

The Mk5P is the latest version of the line of fully closed rebreathers developed by Cis-Lunar. This unit was recently displayed in England at the IANTD UK conference in April of 1997.

There are many advanced features incorporated into the design of the Mk5p. These include multiple O2 sensors, multiple microprocessors, multiple power sources, and multiple displays. All systems are designed to operate together, or in the event of the failure of any individual system, independently.

The counterlung features a dual "over-the-shoulder" design which includes integrated "shoulder port traps" which route water leakage from the mouthpiece into the counterlungs where it may be purged by the diver. The front breathing hoses are doubly armored and the rear hose is singly armored in addition to being completely shielded by the backpack.

A real time, constant pO2, trimix decompression computer is included in the long list of features contained in the Mk5P. This decompression computer will allow multiple gas switches during the dive including open circuit bailout. Throughout the gas switches, the computer will continue to track and calculate the decompression profile. A heads up display is available which provides critical information on pO2, decompression, and system status at a glance.

An interesting inovation in the center section is a hydrophobic membrane which is used to help protect the scrubber in the event of flooding the breathing loop. This membrane allows the passage of breathing gases, without allowing water to pass through. This also makes it possible to change the scrubber under water during a decompression stop.

Bailout is via a convertible mouthpiece which is switchable on the fly from closed circuit rebreather use to open circuit bailout. Extra gas, breathable as a high flow open circuit feed to the mouthpiece (which may be used with a full face mask ) or as alternative gas for closed circuit use, may be connected to the system with quick connect fittings.

The Inside of the Mk5P

Rich Pyle with the Mk5P

Rich Pyle has been using the Cis-Lunar Mk4 and recently the Mk5P for his research and his passion. Rich is a self-proclaimed fish nerd who often makes dives in excess of 300ft in order to discover, collect and categorize new species of fish.

There is a patented chest mounted "Gas Control System" which includes manual add valves for the oxygen and diluent as well as an O2 lock in the event of a failure in the "open" position of the computer controlled gas addition system. . The Mk5P is fully compatible with mixed gas and has the ability to switch gases on the fly through the use of gas select valves for both the diluent and oxygen supplies. In an emergency, it can use the safety locked select valve to isolate some or all of the gas supplies. The control panel allows the unique capability of accessing ALL gas supplies, whether on or offboard, in open circuit mode or with a full face mask. This switching ability extends to the O2 supply, but this is protected with an intentional two step activation procedure.


Additional Specs:

The first 30 units are currently in the final stages of production and are scheduled to ship near the end of June. The second production run will included approximately 50 units and will start as soon as the first run of 30 has been shipped.

For more information on the Cis-Lunar Mk5P visit the Cis-Lunar web site or visit the web page sponsored by "Phoenix" . You can also look on the Manufacturers pages on this web site for company contact information.

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Revised: September 07, 2005.