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I now have a copy of `Diver' magazine May 1994 (publ. by Eaton Publications, 55 High St., Teddington, Middlesex (in the west of Greater London) TW11 8HA, tel. 081-943-4288, fax 081-943-4312). The rebreather articles are on pp 23 24 25 (p22 is merely a photo of a diver with a Prism underwater), written by John Bantin, and Dave Crockford (hyperbaric technician at Fort Bovisand (Plymouth, Devon, UK), and BSAC National Instructor). The relevant parts of the articles are, in summary, as follows after the dots. Comments by me are in [square brackets]. Other matter is the opinions of the abovementioned authors and not my opinion. The present tense of verbs means when the articles were written. .................................................................. In the hereinafter-mentioned breathing sets, the soda-lime is treated to be water-resilient. As it absorbs, it and the gas get warm, which is useful in cold water [so much that some industrial (for use on land) oxygen rebreathers have a second canister with coolant in]. Can be used with helium as diluent; Dave describes the effect of switching supposedly nitrogen-tolerant divers from helium to nitrogen to 50m. In the chamber dives, they used Kraken/Carmellan decompression tables, but at 9m coming up switched from their sets to the chamber's 100% oxygen system. The chamber dives were in November 1993. [PRISM] Looks from the back a bit like a triple set, but the middle cylinder is the canister. Bag on the chest. One gas, which is usually Nitrox 32 or Nitrox 36 (= 32% or 36% oxygen). The bag gradually gets fuller; the surplus is dumped every 2 minutes by an automatic dump valve like in drysuits, to stop diluent from accumulating. Not stated how the gas flow rate is kept right for this to happen [but other sources say the diver must keep it set thus manually]. ppO2 meter that the diver can read. A diffuser can be put over the blowoff valve to break the bubbles into a fine mist. Dave found that to make the blowoff valve work he had to tilt his body slightly, same as with a shoulder-mounted drysuit blowoff valve. Promises to be useful in biology, to avoid bubbles scaring wildlife. Canisters made in 1hr, 2hr, 4hr, 6hr sizes. 4hr size typically with twin 6 liter nitrox cylinders. Special membrane (composition still secret) in canister that lets gas but not water into the canister; any water goes into a sump in the bottom of the canister box. To save gas, avoid repeated mask clearing or [with a mouthpiece] exhaling through the nose. To avoid getting water in the system, the shutoff valve in the mouthpiece must be operated manually whenever the mouthpiece is removed [which must be remembered well by aqualung-trained divers who often casually remove the mouthpiece, or let their bite get slack so water leaks in. That is why I prefer a fullface mask with a rebreather.] Can fit in a stab jacket, [but the stab jacket's cylinder-holding strap or straps go round both cylinders and the canister and so must be long.] Uses about 20% as much cylinder contents as an aqualung. With pure oxygen cylinders can be used as a resuscitator. Planned price 2000 to 2500 pounds. 50 sets being made. Tested in chanber dives at Fort Bovisand: all tests went well. [When article was written] there had been 250 man-hours of Prism wet [= not in a chamber] diving, average depth 15m, in sea and in fresh water. [CARMELLAN and OCEANIC] are developing a closed-circuit sport-diving rebreather, expected price 3000-plus pounds, release expected in Sept/Oct 1994. Tested in chamber dives at Fort Bovisand: all tests went well. Not stated if it can be switched to pure oxygen mode for decompression. [BIOMARINE MK 16] American. Uses Carmellan technology. Computer-controlled. Has been dived beyond 160m. Everything in a backpack. Is called a `commercial unit'. Price not stated. In a photo there is a big disk-shaped part in the upper part of the backpack, giving it a shape a bit like a Ghostbuster's proton pack. [I saw an early Carmellan set that shape in Nov 1992 at a diving exhibition in Birmingham (UK).] [What is Biomarine's maker's address for enquiries please?]
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