DAN Europe Project
The Voyager is the only rebreather that has been physiologically tested for diving. DAN Europe, the Free University of Brussels (VUB-ULB) and AQUATEK (the manufacturer of the Voyager, now H.B. Technology) have tested the physiological effects of rebreather diving over the last four years.
There are many models of rebreathers but only one system that can offer the versatility, reliability and safety of the Voyager. As part of a joint four-year research project by DAN Europe some of the most internationally recognized experts in diving have tested this high quality life-support system in the most extremes dive environments - deep cave exploration, deep open water dives, altitude diving and ice diving.
Click here to download the results of DAN's research project.
Mechanical versus electrical
Together with H.B. Technology, Beyond Scuba is working to teach the dive community that rebreathers are safe, simple to operate and affordable.
Rebreather operating systems can be divided into two broad categories:
· Mechanically-controlled
· Electronically-controlled
The main difference between these two types of units is the way the oxygen level is maintained in the breathing loop. The Voyager is a mechanically-controlled unit that uses a mass flow regulator to replace the complex system of solenoids and wires in an electronically-controlled rebreather with a simple constant flow of oxygen molecules.
Most closed-circuit rebreathers use computer-controlled electronics together with three oxygen sensors. This is by far the most complex and expensive type of rebreather. Such units require a higher level of attention before, during and after the dive, and more routine and long-term maintenance.
Mechanically-controlled systems like Voyager offer a new concept in rebreather design. The primary goal of a mixed gas closed-circuit system is to deliver to the diver a gas mix that contains a constant partial pressure of oxygen.
Not all rebreathers are created equal. While all manufacturers perform some testing not all rebreathers are evaluated in the same way. With rebreathers a more expensive unit does not necessarily mean a better unit. As with any piece of equipment the user must determine the desired objective, then select the gear accordingly. The Voyager's unique modular system allows the diver to adapt the unit's configuration to suit the dive. The Voyager is world’s only rebreather that operates in both semi-closed and closed-circuit modes and that can use all types of scrubber andbreathing gasses in all percentages. Nothing can beat the use of the best set-up for a specific objective, such as very deep dives, long dives or getting close to marine life.
Electronically-controlled rebreathers
In elctronically-controlled rebreathers the oxygen partial pressure is maintained at a constant value by an oxygen-sensing and automatic addition system. As the diver consumes oxygen an oxygen sensor detects the fall in oxygen partial pressure and signals an oxygen valve (solenoid) to open, allowing a small amount of pure oxygen to be added to the breathing circuit from a cylinder. Oxygen addition is matched exactly to the metabolic consumption of the diver.
The weakness of electronically-controlled rebreathers is their reliance on electronics to control the concentration of oxygen in the breathing loop. As any underwater photographer knows electronics and water, particularly salt water, do not mix. Indeed closed-circuit rebreathers have earned a somewhat notorious reputation as being unreliable, largely due to failures in the electronic oxygen control system leading to either too much or too little oxygen in the breathing loop. Because of this electronic closed-circuit rebreathers are in many ways inferior and more dangerous to use. Having the most complex design they carry the greatest risk of both mechanical and electrical failure. Another concern with these units is their reliance on battery power. All electronic-closed circuit systems use batteries to control automatic oxygen addition. If these batteries fail then the unit simply will not operate.
Because of their complexity, multiple potential sources of failure and widely differing designs there have been a significant number of deaths amongst divers using electronically-operated systems. The best solution is always the simplest. The simple mechanical design of the Voyager oxygen addition system eliminates all three possible points of failure. This is what divers require from their critical life-support system.
Mechanical-controlled rebreathers
The conventional design approach of manufacturers of closed-circuit rebreathers is to use solenoids that are controlled by a microprocessor. If the oxygen partial pressure in the breathing loop is above a set point however the unit does nothing to alter the gas content. This is highly significant because even if the oxygen partial pressure becomes extremely high, as might occur if the oxygen injection system were to stick open or if the diver descends very rapidly, the unit will do nothing to bring the oxygen partial pressure to a safe level. If a solenoid fails its valve normally sticks in the closed position, though some failures will result in the solenoid valve sticking open. This can lead to Central Nervous System oxygen toxicity if the user does not properly monitor the oxygen partial pressure.
Unlike electronic closed-circuit rebreathers the Voyager does not rely on electronic controls to mix a diver’s breathing gas. The Voyager gas addition is managed by a simple mechanical device that provides a constant mass of oxygen free-flowing steadily into the breathing loop. The unit has only one moving part in its oxygen addition system, thus eliminating a failure point associated with solenoid valves. This also reduces the likelihood of potentially costly repairs. The amount of oxygen added is based upon the divers’ normal metabolic range, which only varies slightly over the course of any dive. This type of design provides a simple solution and is straightforward to set up, operate and maintain.
Design Safety
The Voyager rebreather provides the optimal benefits of a closed-circuit rebreather system while dramatically reducing the risk of three concerns of diving with a rebreather: hypoxia, hyperoxia and hypercapnia. Due to the Voyager’s simple mechanical design the likelihood of any of these conditions arising lies in the control of the diver.
Hypoxia (lack of oxygen) & Hyperoxia (too much oxygen)
Some divers believe an industry-led misconception that oxygen metabolism can increase as much as six-fold during heavy periods of heavy exertion. This is true on the surface but not underwater.
Underwater your metabolic rate can drop 5-10% below your normal level of oxygen consumption if you are at rest or relaxing depending on your height and body size. Conversely if you start swimming har d, against a current for example, your metabolic rate may increase by 40-90%. While it is possible to double your metabolic rate it is very unlikely to happen.
Some divers worry that the oxygen partial pressure inside the breathing loop might drop quickly to a hypoxic level if they start swimming too hard, causing them to fall unconsciousness and drown unless they add more oxygen. Despite these fears the oxygen partial pressure does not vary widely during periods of exertion. It is in fact highly unlikely that the gas inside the breathing loop will drop to a hypoxic level even during increased workload. Why - because it is not physiologically possible for a diver to maintain high enough levels of physical exertion over an extended period of time without first being overcome with exhaustion. It is therefore up to the diver to take steps to ensure a continuous life-sustaining gas mixture in the breathing loop at all times.
Variation in the oxygen partial pressure is further reduced with depth. The deeper the depth the denser the volume of gas in the breathing loop. This means that there is a greater number of oxygen molecules making up the internal partial pressure of oxygen that the diver breathes. The shallower the depth the more the partial pressure can vary, since there are less molecules of oxygen available to consume within the loop.
Oxygen addition in the Voyager rebreather is controlled mechanically with a safeguard. This operating concept prevents the oxygen level within the breathing loop from rising accidentally to hyperoxic levels. Oxygen is added at rate based on a diver's normal metabolic need. It is extremely unlikely that the oxygen partial pressure will rise above a set point. The only way the oxygen level can increase without manual intervention is if the diver's metabolic rate drops below the flow rate of oxygen addition. If you are at rest on the bottom your metabolic rate will drop approximately by 5-10%. This is however only a small change that is barely noticeable when using with an oxygen monitor and it would require a long period of time for the oxygen level in the loop to rise above a safe level.
The Voyager system has demonstrated repeatedly in tests by DAN Europe to have far less variability in oxygen partial pressure than electronic closed-circuit rebreathers. It is now apparent that free-flowing oxygen is a much simpler and safer means of operating a closed-circuit system.
The Voyager system is simpler, more versatile and more intuitive to use than any other rebreather available today!