RESA Standards; Teaching Mod 2 and Mod 3 Rebreather Courses

The Rebreather Education and Safety Association (RESA) was developed in order to aid in improving the education and safety in the rebreather industry and to ensure that the appropriate framework is in place that suits our growing industry.

This is a RESA standard for rebreather instructors that are already certified to teach Mod2 or Mod3 on one rebreather, and want to teach Mod2 or Mod3 on another rebreather.

RESA have been actively discussing rebreather training at the Normoxic (MOD 2) and Hypoxic (MOD 3) Trimix levels. Some instructors have been teaching advanced level courses to divers on units where the instructor only has minimal training. These instructors have only been required to pass a user course on the second and subsequent units. There have been no further industry-wide standards such as a minimum number of dives to have this privilege. Also, there has been no evaluation to prove that they understand the units properly.

Below is the standard that RESA members voted on. This standard was approved with a unanimous vote from both RESA Manufacturers and RESA Training Agencies. This standard is for Normoxic (MOD 2) and Hypoxic (MOD 3) Trimix training on additional rebreather’s only. For entry level training (MOD1) the instructor is required to be trained as a unit specific instructor by an IT for the specific rebreather.

The implementation date will be 1st January 2014.

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Rebreather Cell Warning Advice by Mike Fowler, Silent Diving

At some point in your CCR diving career you are likely to encounter a cell warning. Besides pressing the right button to make it go quiet, do you really know what to look for or do about it?

Cell warnings are given by AP rebreathers when one cell deviates from the average of the closest two by more than 0.2 bar. It is the machine's way of telling you that all is not well and you need to check it out. It might be just that one cell is reacting slower than its partners or may be something very serious indeed.

The important point is that YOU need to check it. Just assuming the machine will take care of you and suppressing the warning is extremely dangerous. Understanding how the machine works is a valuable tool in your armory. It might seem obvious but it is always worth remembering that when diluent is added to the loop you expect the PO2 to fall, and when oxygen is added you expect the PO2 to rise.

Ambient Pressure Diving, Martin Parker, Silent Diving, Mike Fowler, rebreather cell warnings, Rosemary E Lunn, Roz Lunn, The Underwater Marketing Company, Rebreather Forum 3, RF3, diving safety, Evolution, Vision electronics


With the Vision electronics you can do all sorts of diagnostics that can help you to decide on the correct course of action in the water but also after the dive the download allows you (and the factory or Silent Diving) to diagnose what happened.

A diluent flush is seen as a great method of checking cells and at the same time ensures you have a life supporting gas mixture in the loop, but from observing divers and downloads it is clear that very few do a diluent flush effectively enough to check cells. You must watch the display as you are doing to flush. The problem often arises from the fact that as soon as the PO2 goes below the setpoint the machine adds oxygen, what’s happening is you are trying to lower the PO2 at the same time as the machine is trying to raise it. The simple answer is; change to the low setpoint (by pressing and holding the middle button, regardless of whether you use Manual, Auto or Gradual setpoint change methods) and then do the diluent flush for 5 - 10 secs.

Providing you are using an appropriate diluent for the dive, one that is not too oxygen rich and you do the diluent flush properly, the displayed PO2 should drop very rapidly to the expected value for that diluent at that depth. The expected PO2 is easy enough to calculate if you measure depth in meters, but not quite so straight forward if you measure depth in feet. You just need to go into Menu mode, by pressing the outside two buttons and scrolling through until you get to the PO2 screen where it shows you the expected PO2 at this depth should you flush with diluent or oxygen.

You are looking for the reaction speed of the cells, do they fall at roughly the same speed and do they reach the expected value? If for instance, only cell 1 hits the expected value, then when you change back to the high setpoint that cell is most likely to be the accurate cell at the high setpoint. As oxygen is added watch the cell displays to see if they rise at roughly the same speed and do they get to setpoint?

APD Handset, Ambient Pressure Diving, Silent Diving, Matthew Outram, Rosemary E Lunn, Roz Lunn, The Underwater Marketing Company
Image by Matthew Outram


Cell warnings can occur for a number of reasons, it might be that one cell simply reacts slightly slower to a gas change, but more importantly it could be letting you know that the machine’s voting logic is no longer a valid way to keep you alive.

When this happens don’t blindly continue thinking the same as the machine, believing the closest two are accurate.

A diluent flush may be all that you need to do to get rid of the cell warning but a persistent cell warning is telling you that the voting logic is not going to work, and it’s your job to find out which cells are giving the correct values. Just because the machine thinks the nearest two are correct doesn’t mean they actually are, and then once you find out which cell or cells is / are correct, then you can fly it manually.

Once you start seeing two low cells and one 0.2+ bar higher, it would be prudent to lower the setpoint. This would potentially lower the setpoint below the two current limited cells’ outputs, allowing them to work properly again and if successful, lower the high output cell bringing it within the safe PO2 envelope.

You might be thinking this is too much hassle but remember a diluent flush is easy and quick to do and it puts breathable life supporting gas into your rebreather for most of your dives at most depths. Obviously if you are shallow with a hypoxic Trimix, then you would have to do the cell check with an oxygen flush, but with that proviso, it is good practice.

Ambient Pressure Diving support the race to the bottom of the Mariana Trench

We know less about the deepest points on our planet than we do about the surface of Mars. This could all change quite soon because Richard Branson in Oceanic / Deep Flight Explorer and James Cameron in Deepsea Challenge are currently racing to the lowest point in the Mariana Trench; the Challenger Deep. This lies 6.83 miles below the ocean and it's the first extensive scientific exploration in a manned submersible of the deepest spot on Earth.

Two rebreather manufacturers have been quietly involved with this project. Branson has embraced the Poseidon Mark VI as his bailout, whilst Cameron is using Ambient Pressure Diving's technology for life support within the submarine.

James Cameron, Ambient Pressure Diving, APD, rebreather, Deepsea Challenge, Mariana Trench, Richard Branson, Poseidon Poseidon Mark VI, exploration, deep sea diving"Up until today we've had to keep schtum about our involvement on this project", stated Martin Parker.  "We're aware that Cameron has just finished Deep trials in the New Britain Trench.  The Deep Sea Challenge Team have spent the last four weeks off the Coasts of Papua New Guinea and New Britain mounting a series of increasingly deeper dives to prepare for James Cameron's dive to the bottom of the Marina Trench. Surpassing 8,000 metres (actual depth 8,221 metres) for several hours James Cameron is the deepest solo submarine pilot and is in the deepest operational submarine".

Ambient Pressure Diving is responsible for keeping the pilot alive in the submarine - not a small role.

"Our job was to design and manufacturer the complete automatic life support system in the submarine. This includes the primary system and an identical back up system which can be used in a closed circuit mode in an emergency. As you'd expect the life support technology is running smoothly, removing the CO2 and controlling the PO2 in a similar way to the way we do in our standard rebreathers. The main scrubber system is fan driven, powered from the sub...should that power be lost then the pilot can move to the bailout rebreather. In total he's got about 70 hours of life support depending on his work rate. The data is stored on board the Vision system but we also send it live to the on board PAC from where it is transmitted to the surface every 3 mins.

I am very proud to be part of the build team, and exceedingly proud of our in-house engineers and development team here in HelstonAmbient Pressure Diving, Martin Parker, Silent Diving, Rosemary E Lunn, The Underwater Marketing Company, rebreathers who delivered the finished system in four months, from award of contract.  The fact that we used our standard rebreather components and re-packaged them gives us a massive boost in delivery capability and most importantly reliability.

We are in daily contact with the ship, receiving dive download data for cross-checking so that we can support the team out there with advice....these are truly exciting times."

Follow this link and if you look hard enough inside the sub you'll see APD's logo.

David Parker of AP Valves

We regret to announce that David Parker, Company Chairman and co-founder of AP has died.

He helped shape British diving over four decades, initially inventing and then manufacturing the AP Valve (the Angela Parker Valve).  This very simple and reliable breathing valve allowed divers to breathe the emergency air carried in the small ABLJ bottles fitted to the Fenzy and later the Buddy jackets.  Whilst it seems impossible to imagine now because almost every diver carries an alternative air source, ie an Octopus, this wasn't always the case. When the AP Valve was invented alternative air sources were just a pipe dream, hence this valve was much valued because it was an effective way of getting air to breathe in those first critical moments of an "out of air situation".

In 1972 David created the first Buddy buoyancy jacket and it was one of the first manufactured with a direct feed low pressure inflator.  Two years later in 1974 David again was an innovator producing polyurethane HF welded buoyancy jackets - the only sensible production technique that is used today for all BCs and Counterlungs.

He also invented the self-sealing surface marker buoy and was running the company when the Buddy Pacific, Arctic, Sea King, and Commando jackets were developed and first sold.

David Parker was a founding member of the North Warwicks Sub Aqua Club and was BSAC Instructor No.177.

In 2007, he was awarded a much deserved Lifetime Achievement Award by Diver Magazine for his lasting contribution to the diving industry. As of today's date, the only lifetime achievement award they have made.

He leaves behind an incredible legacy in the shape of AP Valves and Ambient Pressure Diving.