Left : Prism II fully prepped and ready to dive
Although the majority of diving worldwide is undertaken on traditional open circuit scuba , there ’ s been a steadily-growing market for Closed Circuit Rebreather ( CCR ) diving since the first commerciallyavailable models hit the market during the late 1990s .
Since then there have been a host of different models from different manufacturers . Some have stood the test of time and moved onwards and upwards , while others have remained in development hell , or fallen by the wayside .
The basic premise of any CCR is the same . Unlike scuba , where gas is exhaled directly into the environment until depleted , a rebreather constantly recycles waste gas through a closed loop , in which a scrubber removes its harmful carbon dioxide content .
CCRs are certainly not for everyone , but if you ’ re looking to extend bottom time without using multiple gasses and an array of cylinders , reduce decompression or simply to get closer to marine life , then they ’ re a compelling option .
Scott Yeardley and the Prism II in action at the surface
Nuts and bolts
The Hollis Prism II has been available in the United States for over five years now but for various reasons – Covid 19 among them – has only just received CE approval , which opens the door for its sale in the United Kingdom .
The UK launch took place at Chepstow ’ s National Diving & Activity Centre ( NDAC ) with presentations from Trevor Leyland , MD of Rebreathers UK ( Prism II distributor for UK , Ireland & EU ) and Justin Hanning , Business Development Manager .
After a sit-down history of the Prism II ’ s development and a strip-down of the unit itself , the attendees were then allocated their own instructor to dive the unit on a one-to-one basis .
The Prism II weighs just over 21kg , with a standard pair of 3-litre tanks , one containing oxygen and the other containing diluent ( in this case air ). The unit will also easily accomodate cylinders of larger sizes if required .
As my own ‘ other brand ’ CCR has over-theshoulder counterlungs , I was intrigued to see that the unit I ’ d be diving was fitted with the neater rear-mounted versions .
While there is not a BSAC Prism II course at present , it ’ s currently in the works and under the supervision of instructor Scott Yeardley from Plymouth-based BSAC School , Sandford & Down , we prepared the unit for my first dive .
Both first stages are of non-swivel design , with ports that allow the standard ( and therefore easily-replaceable ) hoses to take the most direct route from A to B . This eliminates any twisting , or the need for manifolds , and in doing so eliminates potential failure points along the way .
The radial scrubber container is manufactured from a transparent urethane material - the advantage of which is also transparent - as any potential harmful water ingress can be discovered at a glance .
The electronic ‘ head ’ of the system sits on top of the scrubber , held in place via
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