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Drift is Normal. Being a Deviant is Normal. Here’s Why

What causes individuals and organizations to drift from acceptable standards and behavior? Is it an aberration or something to expect, and what can we do about it? Human Factors coach Gareth Lock takes us for a deep dive into human biases and our tendency to drift, and what that means for human performance.

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by Gareth Lock

Header image: a deviant diver on the SMS Cöln, and other pictures courtesy of Gareth Lock, unless noted

In 1994, two US Army Black Hawk helicopters were shot down by two US Air Force F-15 fighter jets over northern Iraq killing all 26 people on board the choppers. When the story hit the media, it was almost unbelievable that two highly professional aircrews being guided by other equally professional operators on the Airborne Warning and Control System (AWACS) aircraft could mistake the Black Hawk helicopters for Mil Mi-28 Hind helicopters. But they did!

In his excellent book Friendly Fire: The Accidental Shootdown of U.S. Black Hawks over Northern Iraq, Scott Snook developed and demonstrated the concept of practical drift, a theory whereby each sub-organisation or team has a certain amount of leeway to undertake their operations. This flexibility acknowledges that you can’t follow the rules exactly to the letter all the time. The problem is that these small deviations compound across the wider system with potential disastrous results; and, importantly, no one appears to recognize that the drift is occurring. Snook’s event map describes a complicated web of relationships between multiple stakeholders—the tasking organisation, the aircrew in the Black Hawks, the F-15 aircrew, and the AWACS control team—all of whom were doing the best they could with their limited resources and quickly changing circumstances.  

Practical drift is similar to the “Normalization of Deviance,” a concept Diane Vaughan developed during her examination of the Challenger Shuttle disaster. Vaugn explored the idea in her 1996 book, The Challenger Launch Decision – Risky Technology, Culture, and Deviance at NASA. Normalization of deviance has been discussed in a number of recent diving blogs in an attempt to explore the acceptance of the (continued) breaking of a single rule. 

Rather than focus on a single rule, we should consider Vaughan’s definition wider than the individual level, and look to a larger scale. “Social normalization of deviance means that people within the organisation become so accustomed to a deviation that they don’t consider it as deviant, despite the fact that they far exceed their own rules for elementary safety.” Neil Richardson, a safety and human factors professional (and colleague of mine) operating primarily in the aviation domain, offers another perspective while addressing the same point: “The Shuttle programme was risk-managed right up until the point it wasn’t and the Challenger and crew were lost.” 

Risk management vs, uncertainty management

Risk management is often mentioned in the “professional” arm of diving and diver training courses—such as dive master, instructor, and instructor trainer courses—but it is rarely covered in detail during “user” courses or sport diving. Despite this lack of formal content and process, we are constantly managing relevant uncertainties with the goal of providing an enjoyable dive for ourselves and our students and reducing the likelihood of having an adverse event. 

The term “uncertainties” has specifically been used instead of “risk” because of the way that we normally make decisions in an uncertain environment. When managing risk, we are often comparing historical analyses of quantitative data to determine likelihood and consequence using the logical or System 2 part of the brain. However, when we are managing uncertainties, we use a different part of the brain—often described as System 1—which relies on pattern matching, cognitive biases and mental shortcuts. Importantly, System 1 is heavily influenced by our emotions, which is why we often react quickly rather than logically. 

Equating “risk” and “uncertainties” is like conflating the “apple” type of decision-making with the “orange” type of decision-making. They are both decision-making concepts, but they have different processes and applications and can lead to different outcomes.

We need to recognize that the uncertainties we deal with while diving aren’t just focused on physical safety/harm, but also cover legal, reputation, financial, psychological, and social uncertainties and their associated outcomes. Research has shown that the fear of psychological harm can be stronger than the fear of physical harm.

In the diving industry, when something goes wrong, the (social) media and “investigations” often focus on the proximal causes—those that are closest in time and space to the event—of what happened. There is a focus on violations, rule-breaking, human error, recklessness, or direct health issues, and only sometimes do supervisory/instructional factors come into the discussion. Furthermore, the media rarely examines “local rationality” (why it made sense for the individual to do what they did) or the immediate or wider organisational and cultural factors that may have been present.

Local rationality

If we focus on the local rationality to start with, we know that the majority of the time we are operating in System 1 mode, which is fast, intuitive, and pattern-matching based thinking. We are not actively paying attention to everything that we’re sensing; instead, we are picking what we think are the relevant or important factors based on our previous knowledge and experiences, focused by our present goals and expectations, and using those elements of information to make a decision. 

Despite what some would think, you can’t pay 100% attention all the time! This means that we are literally ditching billions of bits of sensory data each day because, in real time, we don’t think those bits are relevant or important. When there are pressures that prevent us from being more thorough, we are trying to be as efficient as possible. These pressures might be related to time, money, peer-pressure, fear of failure, fear of non-compliance, or fixation on goals/outcomes. However, the more we get “right” without thinking about all of the incoming stimuli, the more we use this pattern to reinforce our decision and then repeat it. How often have you heard “We’ve always done it this way?”

Maybe an adverse event would provide a learning opportunity? Unfortunately, the likelihood of adverse events serving as cautionary tales is entirely dependent upon biases in our thinking and how those biases inform our interpretation of an event, adverse or otherwise. The following is a list of biases:

  • Outcome bias describes the tendency to judge serious events more critically than minor events. This is because we disconnect the quality of the outcome from the quality of the decision. For example, those involved in a fatality with the same conditions as a non-fatality will be treated more critically; a poorly performing regulator that free-flows in 10 m/33 ft of cold water will be treated differently from the same regulator that free-flows in 40 m/131 ft of cold water because the consequences are more severe.
  • Fundamental attribution bias is the tendency to attribute causality of an adverse event involving someone else to the individual involved rather than the situation or context. This is different to when we personally experience failure, as we often blame the situation or context! Inversely, when we personally experience success, we look at our skills and behaviors; but, when others succeed, we have a tendency to attribute the “opportunities” they had as the cause for success.
  • Distancing through differencing is the tendency to discount failures in others as being relevant to ourselves because we are different to the other party in some way, even if the general conditions and context are the same. A recreational OC diver may forget part of their pre-dive sequence because they were distracted but an experienced OC technical diver may believe that they wouldn’t make that same mistake, even though the conditions were the same.
  • Hindsight bias is the tendency to think that, if we had been in the adverse situation, we would have known at the time what the adverse event would have been and would have responded differently. Part of this is because we are able to join the dots looking backwards in time, recognising a pattern that wasn’t apparent in the moment.

Rewards

As a result of these biases, we aren’t very good at picking up small deviations in procedures because we experience “good enough” outcomes, and we are “rewarded” for gradual erosion of the safety margins that the original standards were created to address:

• We saved time (or weren’t late) as we skipped through the checks quickly. 

• We saw more of the wreck or reef because we extended the bottom time and ate into our minimum gas margins. 

• We managed to certify a few more students this month which helped pay the bills, even though we didn’t cover everything to the same level of detail that we normally do.

• We got some really great social media feedback because we took those divers somewhere they hadn’t been before—and shouldn’t have been either—but they loved it.


Coming 24-25 September 2021 to a Laptop Near You!

Rewards come in all sorts of shapes and sizes, but the common factor is the dopamine rush: Our brains are wired to favor the feel-good rush of a short-term gain over the prolonged reward of a long-term gain. On the other side of the coin, we are also willing to sacrifice a potential major loss in the future if there is a guaranteed minor loss now. For instance, imagine that you’re entering the water for the “dive of a lifetime” in cold water with a regulator setup that doesn’t breathe too well. You weren’t able to get it serviced because of time/money issues. At the end of this particular dive, you have to do a gas sharing ascent; someone else was out of gas due to an equipment failure, and both of your second stages freeflow and freeze, due to poor regulator performance, increased gas flow and the cold environmental conditions. This resulted in two people who were now out of gas and making a rapid ascent to the surface. 

In hindsight, we can see where the failures occurred. But, in real time, the erosion of safety margins and subconscious acceptance of the increased “risk” are likely not considered. In mid-July 2021, I gave a presentation to Divers Alert Network Southern Africa (DAN SA) on the topic of setting and maintaining goals and how goal focus can reduce safety. 

Credit: DAN South Africa

Organisations drift too

This article opens with the topic of normalization of deviation as it related to NASA and the Challenger Shuttle loss. The gradual, imperceptible shift from an original baseline through a series of “risk managed” processes and activities resulted in a “new” baseline that was far from acceptable when considering the original safety argument. This isn’t the first time an organisation has drifted, nor will it be the last. 

Organisations are made of people, and there are reward systems in place within organisations which lead to a conflict between safety, workload, and financial viability. The image below from Jens Rasmussen shows this tension and the “safety margins” that are perceived to be in place. The difficulty is that we don’t know how big the gap is between the margin and catastrophe, so we keep pushing the boundaries until we get some feedback (failure) and hope that it isn’t catastrophic.

“Risk Management in a Dynamic Society: A Modelling Problem” Rasmussen, 1997

Another way of looking at this tension and drift is to use a framework from the Human and Organisation Performance (HOP) domain called the Organisational Drift Model from Sidney Dekker.

The premise here is that safety is “created” by the development of rules, processes, procedures, and a culture which supports adherence to these standards or expectations. In the modern safety domain, these rules, processes, and procedures are called “Work as Imagined” or “Work as Prescribed.” They rarely match exactly the operational environment to which they are going to be used. There are good reasons for that; you cannot document everything that you want your people (instructor trainers, instructors, dive masters, and divers) to do in every circumstance, so there will be gaps between what should be done and what is done. These gaps are filled in by experience and feedback. Some call this common sense, but you can’t develop common sense without personal experience!

As time progresses, there is an increased gap between the “Work as Imagined” (black line) and “Work as Done” (blue line). This gap is risk or uncertainty to the organisation. Not all drift is bad though, because innovation can come from drift as long as it is recognized, debriefed, and intentionally fed back into the system for improvement.

At the same time as individual and team performance is drifting, the operational environment is changing too. There are accumulations which are adding uncertainty/risk to the system: old or outdated equipment, external requirements changing, legislation changes, change of purpose of equipment or accommodation/infrastructure, and many others. Often these accumulations are dealt with by different people in an organisation, so the compounding effect is not seen.

The gap between “Work as Done” and the “Accumulations” line is known as capacity within the system. This capacity is managed by individuals, taking into account their experience, knowledge, skills, and attitudes towards and within the diving environment. Safety does not reside in paperwork, equipment, or individuals; it is created by those within the diving system taking into account all of the resources they have and the pressures they face while balancing workload, money, and safety dynamically. 

However, when the capacity runs out (when the Work as Done line crosses the Accumulations line) an adverse event occurs. This event is now under the spotlight because it is obvious and cannot be hidden, especially if it is very serious. Hindsight clouds our ability to learn because we think the gaps must have been obvious. Effective organisational learning to prevent drift doesn’t need an adverse event. What it needs is a curious mind and the motivation to improve. If we stopped time 5 seconds before the lines crossed, while we still had capacity, then all of the learning opportunities would still be present and we could examine them. We would be able to see what accumulations are occurring, we would be able to see Work as Done actually was, and we would be able to increase the capacity of the system thereby reducing the likelihood of an adverse event. But that requires organisations to recognize that adverse events are outcomes from a complex system with many interactions, and where they set and demonstrate the acceptable standards and expectations. The absence of adverse events does not mean that you are operating a ‘safe’ system.

If drift is normal, what can I do about it?

First, recognize and acknowledge that drift exists. We all have a tendency to drift. If drift is occurring, look at the conditions that are causing the drift without focusing on the drifting individual themselves. This could be time pressures, financial pressures because of ‘cheap’ courses, lack of experience, high turnover of staff and low commitment to the sport by divers or dive professionals. 

Secondly, create an environment where feedback, especially critical context rich feedback, is the norm. This has multiple benefits: 

  • Individuals find out where they are drifting from the standards/expectations which have been set.
  • Organisations find out if their standards/expectations are fit for purpose and where issues about compliance are arising.
  • Accumulations are identified in a timely manner and addressed.

There are a number of blogs on The Human Diver website and our Vimeo channel which help to develop a learning culture, understand how drift occurs via human error, and how to develop both a psychologically safe environment and a Just Culture. In terms of having an immediate effect, a post-dive/post-project debrief is one of the best methods, and you can download the DEBRIEF framework I created to help facilitate critical, learning-focused debriefs from here: www.thehumandiver.com/debrief  

Remember, is it normal to err. It is what we do once we’ve made the error that matters when it comes to creating positive change in the future. If we focus on the individual and their behavior, things are unlikely to improve. However, if we look at the conditions and context, then we have the opportunity to reduce the chances of an adverse event in the future. And if we share those lessons, it isn’t just our organisation or team that improves, the diving community can too.

Additional Resources

Be There or Be Deviant: HF In Diving Conference 24-25 September 2021


Gareth Lock has been involved in high-risk work since 1989. He spent 25 years in the Royal Air Force in a variety of front-line operational, research and development, and systems engineering roles which have given him a unique perspective. In 2005, he started his dive training with GUE and is now an advanced trimix diver (Tech 2) and JJ-CCR Normoxic trimix diver. In 2016, he formed The Human Diver with the goal of bringing his operational, human factors, and systems thinking to diving safety. Since then, he has trained more than 350 people face-to-face around the globe, taught nearly 2,000 people via online programmes, sold more than 4,000 copies of his book Under Pressure: Diving Deeper with Human Factors, and produced “If Only…,” a documentary about a fatal dive told through the lens of Human Factors and a Just Culture. In September 2021, he will be opening the first ever Human Factors in Diving conference. His goal: to bring human factors practice and knowledge into the diving community to improve safety, performance, and enjoyment.

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Diving Safety

What Happened to Solid State Oxygen Sensors?

The news in 2016 that Poseidon Diving Systems would be incorporating a solid state oxygen sensor in their rebreathers sent a buzz through the rebreather community. Galvanic sensors, along with their legacy-1960s “voting logic” algorithms to boost reliability, had long been considered the weakest link in closed circuit rebreathers. Many heralded Poseidon’s subsequent 2017 roll-out as the dawn of a new era in rebreather safety. Five years later, Poseidon remains one of two companies (the other strictly military) to have adopted optical sensors. Technology reporter and tech diver Ashley Stewart examines some of the reasons why.

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by Ashley Stewart.

Header image: Karst Underwater Research (KUR) rebreather divers at Weeki Wachee. Photo by Kirill Egorov

For years, it’s been said there’s a revolution coming for the closed-circuit rebreather— a new, more reliable, safer replacement for the traditional electro-galvanic oxygen sensor, widely considered the weakest component of rebreathers. In March 2017, that revolution looked to be just over the horizon. Poseidon Diving Systems began shipping an offboard solid state sensor to supplement the MKVI’s and SE7EN’s galvanic sensors and offered to license the technology to other manufacturers. Though Poseidon subsequently incorporated the solid state sensor into its SE7EN rebreathers, nearly five years have passed, and not much else has changed.

Poseidon remains the only manufacturer using solid state sensors in recreational rebreathers. No other companies have licensed Poseidon’s technology. Major tech diving manufacturers—including JJ-CCR and Divesoft—say they don’t believe the technology in general is ready for use in rebreathers. Some manufacturers worry that the sensors won’t function accurately in humid environments over a wide range of pressures, and they claim that addressing these challenges will be costly. Meanwhile, divers who tested Poseidon’s sensors offered mixed reviews, and even the inventor who sold the sensor validation technology patent to Poseidon believes they should be used along with traditional sensors. (Poseidon gives divers the option of combining the sensors).



Poseidon’s solid state sensor integrated into the SE7EN rebreather. Photo courtesy of Poseidon.

Oxygen sensors are the enabling technology that made mixed gas rebreathers possible, replacing rebreathers that could only be used with pure oxygen. In 1968, marine scientist Walter Starck introduced the first commercial CCR, called the Electrolung, which used polarographic sensors. The next year, BioMarine Industries launched its CCR-1000, the predecessor of the US Navy’s Mk-15/16. The unit was the first mixed gas rebreather to use galvanic sensors, which do not require a power supply. 

In addition to removing a diver’s exhaled carbon dioxide, a rebreather must measure and maintain a safe and efficient level of oxygen, as measured by the partial pressure of oxygen, or PO2, via oxygen sensors.

Measuring PO2 correctly is critical, and failures can be fatal. Too little oxygen can cause hypoxia and loss of consciousness, and too much can result in central nervous system toxicity and convulsions. Since sport divers began using CCRs over twenty years ago, both conditions have caused numerous drowning fatalities.

With the exception of Poseidon and military manufacturer Avon Underwater Systems, modern close circuit rebreathers have more or less used the same type of sensor since the 1960s. Rebreathers typically use three galvanic sensors, averaging the readings of the two closest sensors and ignoring the third in a protocol called “voting logic,” originally created by Starck in response to the sensors’ noted unreliability.

Even with this voting logic, however, the sensors can be unreliable (See “PO2 Sensor Redundancy” in Additional Resources below). The galvanic sensors are cheap and time-tested, but they need to be recalibrated before every dive and expire after about a year. The new sensors—called “solid state sensors” or optical sensors—are expected to be more precise, reliable, and durable, though significantly more costly.

An illustration of luminescent quenching technology

Galvanic sensors are essentially wet-cell batteries that generate a millivolt current proportional to the PO2 in the loop. Conversely, Poseidon’s solid state sensor uses luminescent quenching, wherein a red LED light excites the underside of a special polymer surface, which is covered with a hydrophobic membrane and exposed to the gas in the breathing loop. A digital color meter then measures the responding change in fluorescence, which is dependent on oxygen pressure, and an algorithm calculates the PO2.

Experts more or less agree that the right solid state sensor could make rebreathers safer, but the market is split on whether the technology is ready for use in rebreathers and just how much better they’d have to be to justify the cost.

Field Test Results

Poseidon advertises its sensor as “factory-calibrated and absolute, delivering unsurpassed operating life, shelf life, and calibration stability.” Richard Pyle, a senior curator of ichthyology at Hawaii’s Bishop Museum who works with Poseidon-affiliated Stone Aerospace, has tested Poseidon’s sensors for years, initially as a passive offboard check against Poseidon’s traditional galvanic sensors. Later, in November 2019, he said he began testing Poseidon’s prototype with the solid state sensor as the primary sensor in the unit. “From my perspective as a rebreather diver, this is the most significant game-changing way to know what you are breathing,” Pyle said. “We will never go back to the old oxygen sensors.”

Poseidon divers at 110 m/359 ft. Photo by John L. Earle

Pyle said he’s yet to fully analyze the data he’s collected to compare the performance of the solid state sensors against the galvanic sensors, but that  he’s had zero failures with the solid state sensors in the time he would have expected to have 50 to 100 failures with the galvanic sensors.

Likewise, Brian Greene, a Bishop Museum researcher who has tested the Poseidon sensors with Pyle, estimated that he’s made hundreds of dives with the solid state sensors without failure. But, not everyone has had this experience.

Sonia Rowley, an assistant researcher at the Department of Earth Sciences in University of Hawai’i at Mānoa, told InDepth that she experienced a variety of repeated failures when testing Poseidon’s system alongside Pyle beginning in 2016 and 2017, and Rowley dictated to InDepth specific dive logs detailing many of the failures. She wrote about her experience in the book “Close Calls.

Poseidon CEO Jonas Brandt said the company has tested the sensors since 2017 at different depths and temperatures, and that it has only seen one possible failure.



Arne Sieber is a sensor technology researcher who said he developed the O2 sensor validation technology used in the Poseidon rebreather and sold the patent to Poseidon. Sieber is now researching uses for the solid state sensor including in the medical market. He told InDepth he believes the best way to incorporate the solid state sensors into rebreathers would not be to substitute one for the other, but to combine sensor types and design a rebreather that incorporates both. 

Traditional galvanic sensors have advantages over the solid state sensors, Sieber said—they’re cheap, simply designed, low-voltage, and time-tested. Also, while solid state sensors are very accurate at measuring low PO2, they become less sensitive at about 1.6 bar, and are more prone to incorrect readings of higher PO2 levels than galvanic sensors. As for whether the sensors can function in humid environments, Sieber said the sensors can work well in liquids, such as when used for blood analysis (though the sensors are used to measure much lower partial pressures of oxygen) and for measuring oxygen content in the sea. Liquid can delay the amount of time it takes a sensor to read a partial pressure, but it does not falsify the results, Sieber said. Of Poseidon’s system, Sieber said, “It’s a good start. It’s very important that someone starts. Someone always has to be the first one.”

Brandt said divers have the option of combining sensors in the company’s SE7EN rebreather, using either two galvanic sensors, two solid state sensors, or one of each, and said it could be argued that using one of each sensor is the most reliable.

Meanwhile, a catalyst may be coming to encourage the development and adoption of solid state sensors in Europe, Sieber said. European Union rules restrict the use of hazardous substances in electrical and electronic equipment, but galvanic sensors (which have an anode made of lead) have been granted an exemption in medical products because there is not a suitable alternative. The exemption is set to expire.

Poseidon’s solid state sensor sells to end users for as much as around $1,500USD, and its SE7EN rebreather units use a maximum of two onboard sensors. [Note: Poseidon sells the sensor for 6800SEK plus VAT from its website, which equates to 944 USD, some outlets in the states sell them for much higher]. Galvanic sensors, meanwhile, cost around $100USD, last one year and divers use three at a time. And, that’s just the cost of the sensors themselves: Manufacturers have to make significant investments in, and upgrades to, electronics systems to accommodate solid state sensors. 

Fathom rebreather lid showing its galvanic sensors. Photo courtesy of Fathom Dive Systems, LLC.

As for how long the sensors actually last, even the manufacturers don’t yet know. Poseidon has some from 2014, and they still work but have to be factory calibrated every two years. Galvanic sensors need to be replaced annually, while solid state sensors are expected to last much longer.

Brandt chalks the debate about its sensors up to competitiveness in the market. “I don’t think anyone likes that somebody cracked the nut,” Brandt told InDepth. Poseidon is ready to share the technology with other dive companies and manufacturers, Brandt said, but there have been no deals to date. “We wanted to raise the bar in technology and safety with the rebreathers, and to be honest, we haven’t said to anyone in this business that this technology is exclusive or proprietary.”

Market Interest

When the company first debuted its sensor, Brandt reported that companies like Hollis and Shearwater Research expressed interest in licensing the technology, but nothing has come so far of those discussions. Brandt did say one manufacturer reached out right before the pandemic. He declined to say which, but shared that it was a European company. Hollis brand manager Nick Hollis said his team recalls a conversation with Poseidon, but that it was back in 2014 or even earlier.

Shearwater director of sales and marketing Gabriel Pineda said the company is still interested in solid state sensors, but they see an issue with the price. “If you make the economic case of traditional galvanic sensors versus solid state or optical sensors, you have to dive a lot, and it takes a long time for these to make economic sense for a diver.”

Of course, Shearwater is not a CCR manufacturer, but the company is interested in seeing whether the sensors would be viable for use with its electronic control system that is used by a majority of rebreathers on the market. Shearwater currently has no immediate plans to license the technology from any manufacturer but Pineda said the interest remains. 

Meanwhile, Poseidon’s solid state sensor CCR is still making headway, Brandt said. The current biggest buyer of the Poseidon units is the military (Brandt said three European Union countries’ forces are actively using the sensors). The sales have continued throughout the pandemic, and, over the past six months, Poseidon has started an upgrading program, allowing divers to add the new sensors to their old units. Poseidon is looking into a program Brandt compares to Apple Care, where customers can pay a fee for maintenance throughout the life of the sensor.

Solid state sensors replace numerous galvanic sensors which have a one-year life. Photo courtesy of Richard Pyle.

Meanwhile, Avon Underwater Systems is using three solid state sensors in its MCM100 military rebreather. Kevin Gurr, a rebreather designer and engineer who sold his company, VR Technology Ltd., to Avon, said the company uses the sensors “because of the increased safety and the decreased user burden as far as daily calibration.”

Gurr, who designed and produced the Ouroboris and Sentinel closed circuit rebreathers at his prior company VR Technologies Ltd., believes it’s the cost that has discouraged other manufacturers. “It shouldn’t be about cost at the end of the day,” Gurr said. “The digital interface is so much safer.”

Martin Parker, managing director of rebreather manufacturer AP Diving, said his company follows solid state sensor development but has yet to come across a sensor that meets its accuracy requirements. One such sensor using luminescence quenching can achieve good accuracy through a replacement disk the user must apply to the sensor surface after each use.

“Having been in the diving business for 50 years, we don’t believe it is on any diver’s wish list to have to re-apply every diving day a new component, as simple as that is to do,” Parker told InDepth. “With no easy external measure of accuracy prior to the dive, it is easy to foresee that many divers would ‘push their luck’ and use the discs for multiple days, then when they get away with it, they would encourage other divers to do the same… with the inherent risk of DCS or O2 toxicity.”

Parker said that he’s aware of two additional sensors under development, but neither has shown a working product yet. He declined to identify any of the manufacturers, citing commercial sensitivity. “Hopefully, we will get these to evaluate in the next 12 months,” Parker said.

Divesoft co-founder Aleš Procháska said he believes Poseidon’s approach to the sensor could “lead to success.” Speaking generally about solid state sensors rather than about Poseidon’s specifically, Procháska said his company isn’t yet utilizing solid state sensors because he believes the sensors are unable to function in humid environments with extreme water condensation and not applicable over a  wide range of pressures. To be able to use one of these sensors in a rebreather, Divesoft wants it to be durable in high humidity, consume less energy, and have a good price-to-lifetime ratio. 

“It is possible to build a CCR with the currently available O2 solid state sensor but not without sacrificing important properties of the breathing apparatus,” he said, such as size and energy. “Overall, the reasons why no one currently sells this technology on the market seems to be quite simple. It’s extremely difficult to come up with a suitable and functional principle that would lead to a cheap, small, and low energy consuming solid-state sensor. Despite this, I do believe that it’s only a matter of time until someone solves this one.” Asked via email about the status of DiveSoft’s own work on the technology, Procháska replied, “Well, as I said earlier, it’s just a matter of time,” adding the text, “Aleš smiles.”

JJ-CCR lid showing its three galvanic sensors. Photo by Kees Beemster Leverenz.

Halcyon COO Mark Messersmith said that divers are slow to embrace new technologies in general, and the current sensors just aren’t deficient enough to merit widespread adoption or the investment from manufacturers. “It’s not unlike many other technologies,” Messersmith told InDepth. “People are often slow to embrace a new technology if the existing technology is functional. The existing tech needs to be vastly deficient, and existing oxygen sensors are still largely functional.” 

The bottom line: Solid state sensors might very well be safer, but there isn’t enough incentive for the market to make them a reality. 

David Thompson, designer of the JJ-CCR, told InDepth they don’t use the sensors because he doesn’t believe the technology is ready yet and research in that area is extremely expensive and difficult for what he believes is essentially a small market. “Analog cells have a long history, and in the right hands are very reliable, easily available, and have a long history of working in a rebreather environment which is very hostile,” Thompson said, adding that high humidity and temperature in a rebreather is a challenge for any sensor. “I am sure it will be in the future, but that future won’t be here yet.”

Additional Resources:

InDepth: Where Have All the Sensors Gone? Assessing the Global Oxygen Sensor Shortage

Rebreather Forum 3 Proceedings: PO2 Sensor Redundancy by Nigel A. Jones p. 193-202

Alert Diver: Oxygen Sensing in Rebreather Diving by Michael Menduno

Wikipedia: Electro-galvanic oxygen sensor


Photo by Daniel McMath 

Ashley Stewart is a Seattle-based technology journalist and GUE Tech 1 diver. Reach her via email: ashannstew@gmail.com, Twitter: @ashannstew, or send a secure message via Signal: +1-425-344-8242.

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