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Letter Reference Lifting of the prohibition on CCR diving

Posted by Mark Allen on January 15, 2015 at 1:15 PM

9 Jan 15


ACNS (Pers)

Copy to:





A. Use of Closed Circuit Rebreathers (CCR) For MoD AT Diving dated 22 May 14.

B. ACNS(Pers) OSWG held on 19 Sep 14.


1. In May 14 you endorsed the recommendations made in Reference A and prohibited the use of Closed Circuit Rebreathers (CCR) until four conditions had been achieved. Superintendent of Diving has now received the six month report from the QinetiQ trial of the replacement O2 sensor and is now content to recommend the lifting of that prohibition.


2. You should note that all four conditions have now been met. You are therefore requested to remove the prohibition on the use of CCRs for AT diving with the following stipulations:

a. Only the APD 16 oxygen sensors are suitable for use in AP Valves CCRs.

b. The trial will continue for another 18 months, should further issues be identified by QinetiQ then the prohibition will be reintroduced.


3. An immediate lifting of the prohibition on CCR diving will enable JSSADC to conduct refresher training in order to allow them to use CCRs on their annual staff training in Feb 15 which will in turn allow courses to be delivered during 2015.


4. Rebreathers in various different forms have been used by JSSADC since 1996 and the current AP Valves Inspiration systems since 2007. More widely they have been increasing in popularity amongst both civilian and military divers due to the significant benefits they offer over more traditional SCUBA equipment. They have been used successfully on some very high profile diving expeditions and were fundamental to the Ex JURASSIC SHARK series which have achieved national recognition, including being twice awarded the BSAC expedition prize by the Duke of Edinburgh.

5. During the annual JSSADC staff training period in Feb 14, a number of faults were reported with AP Valves Inspiration CCRs which led to the following recommendations:

a. A replacement oxygen (O2) sensor should be tested and proved reliable.

b. A Safety Case should be provided for CCRs.

c. A clear training need should be identified for CCRs.

d. The testing of the replacement sensor should be expedited.

6. Testing Regime. The full tests of the oxygen sensors will require two years, it was agreed by all parties that an initial clearance can be given after six months. This will then provide a suitable buffer to allow remedial action to be taken if any issues are subsequently found during the tests.

7. Replacement Sensor. Since Reference A was produced, the equipment manufacturer, AP Valves Ltd, has produced a new model of sensor known as the APD 16. A number of these have been at QinetiQ since early July 14 and Enclosure 1 is a report at the five month point to indicate that they are performing well. QinetiQ inform us that, subject to continued good performance, they expect to recommend in early Jan 15 that the APD 16 sensor is suitable for use by AT divers.

8. Safety Case. This requirement was discussed with Mr Stewart Collier as part of a presentation by CESO(RN) on Safety Cases that he gave to the ACNS (Pers) Operational Safety Working Group (OSWG) during Reference B. He agreed that the extensive documentation & procedures that already exist could be considered to constitute a safety case and therefore he believed that this requirement is already met. The specific list includes:

a. European Standard (CE mark) covering the manufacture and testing of the CCRs.

b. Maintenance procedures carried out in accordance with the manufacturer’s guidelines by suitably trained people.

c. Use of consumables, such as sofnalime and breathing gases, that conform to existing military standards.

d. Training delivered according to the National Governing Body (NGB) standards.

e. Diving conducted under the restrictions of JSP 917 and the NBG Safe Diving practices.

f. Additional mitigating measures are put in place through JSSADC risk assessments and standing orders.

9. Training Need. Annex A explains the rationale behind the requirement for CCRs to be used as part of the Joint Service Adventurous Training (JSAT) scheme and thus taught at JSSADC.

10. Summary. Rebreathers have formed an important component of AT diving for nearly 20 years. They provide AT divers with a unique capability that has been fundamental to the success of several high profile expeditions. Training and diving with CCRs will also allow service AT divers to keep abreast of wider developments in the civilian world.

11. This issue with oxygen sensors has demonstrated that the reporting and rectification process for AT diving is as rigorous as for other service divers. QinetiQ are confident that the new APD 16 sensors do not share the faults of their predecessors. It is now time to remove the prohibition on CCRs to allow JSSADC to deliver their programme for 2015.

{Signed Electronically}



Cdr RN





A. Rebreathers - The Requirement.




1. QinetiQ Five Month Report on APD 16 Oxygen Sensors.





1. Rebreathers provide significant advantages to divers over the traditional open circuit (OC) SCUBA equipment with which most people are familiar. Although once the sole preserve of military divers, civilian development of these items now leads the way with significant levels of adoption amongst more experienced and technical divers.

2. A new generation of semi Closed Circuit Rebreathers (sCCR) have recently been introduced that are likely to bring the benefits to much more junior divers including those who have never dived before.


3. The majority of the gas inhaled by a human is exhaled unchanged with only a fraction of the inhaled oxygen converted to carbon dioxide. Unlike open circuit systems where all exhaled gas is vented to the surface, rebreathers take advantage of this by removing the carbon dioxide and replacing the consumed oxygen. As much less gas is used this means that they require much smaller cylinders and produce far less bubbles

4. This is taken a step further by electronically controlled CCRs which continually monitor the partial pressure of oxygen in the breathing loop. This is used to calculate the optimum nitrogen-oxygen (NITROX) or nitrogen-oxygen-helium (TRIMIX) mixture based on current depth which is then fed to the diver.


5. All rebreathers offer benefits including:

a. Less Bubbles & Noise. Divers wearing SCUBA gear tend to be given a wide berth by much marine life, especially larger animals, due to the amount of noise and bubbles it produces. Rebreathers allow divers to get much closer and are particularly attractive to underwater photographers.

b. Reduced Gas Consumption. Rebreathers use much less gas than SCUBA gear which can allow extended dive times and/or reduce costs.

c. Smaller Gas Cylinders. The smaller cylinders used by rebreathers can make them less bulky and heavy than SCUBA equipment.

d. Warm Moist Gas. The breathing gas delivered to the diver is more pleasant than that received from OC systems. This reduces diver dehydration and is also of benefit when operating in colder climes, such as the UK.

6. Electronically controlled CCRs have the additional benefit of continuously calculating and delivering the best diving gas mixture for a diver at a given depth. This offers a significant reduction in the likelihood of a decompression injury over someone completing the same dive wearing SCUBA equipment. It also offers the opportunity for greater duration dives.


7. The cost and complexity of rebreathers means that they are currently used by the more experienced divers who are looking for an additional challenge or wish to progress to more technical diving. Amongst AT divers they tend to be owned by the instructors and supervisors who deliver the vast majority of Distributed Training (DT) in service clubs and on expeditions. These individuals are absolutely critical for the continued success of AT diving. Preventing them from diving with the CCR equipment that is their pride and joy will inevitably drive them away from the JSAT scheme. The loss will be felt by the junior soldiers, sailors and airmen who would have otherwise been trained by them.

8. There are a small number of expeditions that have used the benefits of rebreathers to achieve specific aims. A good example is the joint service shark tagging team (Ex JURASSIC SHARK) which completed its fourth expedition in 2013. They used the low noise properties of CCRs to get close to sharks in order to fit them with systems to monitor their movements across the Eastern Pacific seaboard. CCRs also formed a significant part of their risk reduction procedures to cover the lack of recompression facilities within a suitable travel duration of their diving locations.

9. The Royal Navy website recently featured Lt Adam Bolton RNR using a CCR to visit the wreck of the HMS Repulse in the South China at a depth of 57 metres. It is a pity that this was done in a private capacity as it would make an excellent aim for a Royal Navy AT diving expedition, especially as the only two previous expeditions to the site were conducted by the Army.


10. There are no reliable statistics for the number of rebreather AT divers although an estimate would place it at less than 5%. What is clear is that there is a very high level of demand for the courses run at JSSADC with each place usually having 2-3 applicants.


11. JSSADC is the lead centre for AT diving across the services and provides Subject Matter Expertise (SME) to HMS TEMERAIRE in their capacity as the tri-service lead for diving AT. It is also the only location at which Sub Aqua Diving Supervisors (SADS) can be qualified and has run rebreather courses for almost 20 years.

12. If CCR diving is to continue to be included in the JSAT scheme then the highest possible quality of training should be offered to those service people who wish to participate. The best way that this can be guaranteed is for the training to be delivered by the lead centre.

13. Ensuring that JSSADC has personnel qualified to dive and instruct CCRs has other benefits. A critical one is that the centre is in the position to offer knowledgeable advice to HMS TEMERAIRE and other single service AT authorities. Staff with CCRs can also ensure that student supervisors and instructors are exposed to them in a suitably controlled environment thus improving the course output.


14. Rebreathers, and particularly modern CCRs, offer significant safety and other benefits. They are largely used by the divers who are critical to the continued success of service AT diving. In addition they provide capabilities that allow service men to conduct expeditions that would otherwise not be possible except at greater levels of risk. In short, CCRs need to continue to be included within the umbrella of AT diving.

15. If CCRs continue to be used for AT then it would seem unusual that they were not taught and used by the lead centre. For this reason it seems sensible to continue to direct JSSADC to utilise them.


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