rebreather diving

Oxygen Measurement for Divers

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LambBookSadly, much of our information about oxygen sensors has been born on Internet chat forums. A lot of that banter is simple anecdotal evidence as opposed to scientific fact. Thankfully, owner of Vandagraph Ltd. in the UK, John Lamb has released his 2nd Edition of “Oxygen Measurement for Divers.” It might not be your idea of a book to curl up with in front of a fire, but it is one of the best investments you can make as a rebreather diver or owner of an oxygen analyzer. Lamb carefully breaks down the measurement of oxygen into abundantly illustrated chapters covering everything from gas laws to blending methods. He dispels some of the misinformation about sensor life and current limitation behavior and offers best management practices for storage and use of common sensors. He reveals the Achilles Heels of sensors and describes future technologies that will improve the measurement of gases in the future. If you want to break through the mire of misinformation and be better informed about diving safety, this is a must-read book.

One of the most important safety practices that Lamb suggests is to replace sensors 12-18 months after manufacture (not after their first use). He describes the normal expected life of a sensor is about 9-10 months in pure oxygen at the surface. He notes that single failure rates are low and multiple failures are rare when these parameters are adhered to. He also advises that correct storage procedures must be adhered to. In his examination of sensors, he believes that temperature is the main cause of early sensor failure. For most divers this means that sensors should be replaced every dive season. For me, that means putting a simple alert in my iPhone Calendar. It is a simple act that can ensure that you are reading accurate PO2 in your rebreather.

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Augmented Reality and a Welcome from Cristina Zenato

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Nat Geo Blog #6 December 9, 2016 – Cristina Zenato

Cristina Zenato, yes, of the Santa Cristina Zenato vineyard, a native of Garda Lake, Italy, has been living in Grand Bahama Island for over 22 years, where she runs educational diving programs and technical diving at the Underwater Explorers Society. When she’s not diving, well, she’s diving – facilitating shark research, cave exploration, and coral reef restoration among many other activities.

Twenty-two years ago I came to the Bahamas from Italy to learn to scuba dive and I discovered they had sharks on the dives here, an animal I have always been fascinated by and attracted to. After only a week I decided to stay and make the Bahamas my home and diving my life. The island was beautiful for me and full of new experiences. The first question I had was about fresh water “how could islands without mountains, rivers, lakes have so much fresh water available?” The answer was right below my feet – underwater caves that dot the forested island.

It wasn’t long after I learned about these caves that I wanted to dive them. I discovered cave diving thanks to Ben Rose. Watching him on my 11th dive ever, floating in water so clear he looked he was in space, I fell in love with cave diving. Since then I have explored every possible available line and when the lines ended I started to explore. I have met a lot of incredible divers along the way and learned a lot from each one of them. Now on this project, here in the pineyards of Abaco, I am watching as two of today’s most prolific cave explorers submerge together for a survey dive. What it comes to mind are two quotes that go very well together:

“Knowledge is power” and “with power comes great responsibility.”

Knowledge on this expedition is present in abundance, with nearly 200 years of cave diving knowledge on this one team. Tom Morris, for example, the cave exploring biologist on the group, at age 70 brings 57 years of cave diving and knowledge to the team. But numbers are relative if this knowledge is not used correctly, you can have 57 one-year experiences or 57 years of experience.

This team is composed of curious explorers, inventive engineers, talented photographers, that have been on every corner of this planet, and they have explored and collected scientific information and communicated it via diverse media. Their knowledge roams in many different directions.

The team members, Dr. Kenny Broad, (25 years of cave diving), Brian Kakuk (30 years), Jill Heinerth (23 years), Steve Bogaert (25 years), Tom Morris (57 years), myself (20 years) do not want to keep all this experience for themselves, they have an invested interest in sharing their knowledge so it can be used to improve the way we live. They want everybody, and especially the local people of the Bahamas to benefit from it.

A central goal of this project is outreach with local school kids and classrooms throughout North America via ‘hangouts’ organized by “Explore by the Seat of your Pants” and National Geographic. Our basecamp is set up in an interactive style, with stations about forestery, fossils, cave diving, cave mapping and herbal medicine. Local school children are organized in teams, rotate through the stations and learn about the integral relationship between the forest, the caves and the fresh water table beneath their feet. Every morning one of us enters the cave to place the pinger to illustrate to the kids topics ranging from cave tracking to pollution transport, and to collect cave critters (that we release at the end of the day). It is indeed the quietest time of the day, my morning meditation. Once back on the surface, the camp comes to a buzz to activities and noises. Later in the afternoon, after all the educational activities have ended we re-enter this world each one with a new task, surveying, photogrammetry, and returning the ancient animals to their peaceful home. Each dive brings back a bit more knowledge that we hope to share in as many ways as possible.



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Travel by Boat of Car with Your CCR

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When using a car and boat, your dive destination may be a lot closer to home, but there are still a few special tips to consider.

  • Bring extra bungee cords for boat travel. Many boats are specifically constructed for single tank divers. The benches may be awkward for a rebreather diver. Bring your own method of securing the rebreather to the bench or the floor.
  • Consider the orientation of your rebreather scrubber. If your rebreather is lying on its back, vibrating on a moving boat or in a car for hours, will your particular canister design be subjected to drastic settling? Some canister designs are equipped with springs that help to resolve settling issues, but if the orientation of the rebreather in relation to the settling forces is incorrect, you could get some channeling of material.
  • Fully assemble and check your rebreather before leaving the dock. You don’t want to be packing sorb on a bouncing boat and also don’t want to capture diesel fumes within the breathing loop.
  • Beware of extreme heat. If you gear is sitting sealed in a hot car for a long period of time, you can damage the oxygen sensors.
  • Beware of extreme cold. If your packed rebreather sits in a freezing car overnight, the moisture in the sorb can freeze causing damage to the canister and dusting in the material itself.
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How We Learn and Stay Sharp

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Taking On New Skills

Brian Kakuk and Paul Heinerth hang on decompression during the NOAA Bermuda Deep Caves Project.

Brian Kakuk and Paul Heinerth hang on decompression during the NOAA Bermuda Deep Caves Project.

Technical diving and specifically, rebreather diving, is a continual learning process. If we closely examine how we learn, we can better prepare for the pitfalls associated with each stage of the learning process.

Gordon Training International is popularly considered to be the originator of the conscious competence model, which describes the steps of learning any new skill. This model is particularly applicable to rebreather diving.

The model describes the first stage of learning as “unconscious/incompetent” or “unconscious-unskilled.” This stage describes the rebreather diver on his or her first day of class; they are unaware of the proper function of the unit and incapable of determining risk. They simply don’t know what can kill them.

Stage two refers, and each stage thereafter, is often associated with a sensation of awakening, when the person feels “like a light bulb went off.” As they make this step forward, they enter the realm of “conscious-incompetence.” At this point, the diver is beginning to understand the function of their unit and able to assess risks, but still needs close supervision.

Next, the learner reaches the point of “conscious/competence.” This may be the point when they complete their initial rebreather training. At this level, the diver has mastered basic controls, has a good assessment of risk and is able to complete self- or buddy-rescue.” This may indeed be the point where they are the safest rebreather diver they can be. They still have a healthy fear that the unit may fail them and are consciously driving the rebreather with great care.

The final stage of learning occurs when the diver reaches the “unconscious/competent” level. This is akin to someone who has been driving a car for a long time. They make their daily commute and barely recall the route they took or the things they saw along the way. When this occurs in rebreather diving, it is often the point when complacency kicks in.

I have often felt that rebreather divers with roughly 50-100 hours after their initial training, may be at the greatest risk, especially if nothing has scared them along the way. A serious gear malfunction in that time frame often frightens the diver back to the previous level of learning, when they become conscious drivers of their unit again. A long absence from diving will also result in the diver stepping backwards in the model until they catch up with their skills and practice.

To avoid the pitfalls of complacency, good procedure and a commitment to pre-dive check-lists and proper pre-breathe sequences are critical. A diver who carefully reviews their personal preparedness as well as their equipment readiness will be better prepared to deal with the issues on the road ahead.



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