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Rebreathers. Self-contained breathing apparatus with active gas supply

Closed Type Oxygen Rebreather

This is the ancestor of rebreathers in general. The first such apparatus was created and used by the British inventor Henry Fluss in the mid-19th century while working in a flooded mine. A closed-cycle oxygen rebreather has all the main parts typical for any type of rebreather: a breathing bag, a canister with a chemical absorbent, breathing hoses with a valve box, a bypass valve (manual or automatic), a bleed valve and a cylinder with a reducer high pressure. The principle of operation is as follows: oxygen from the breathing bag enters through a non-return valve into the diver’s lungs, from there, through another non-return valve, oxygen and carbon dioxide formed during breathing enter the chemical absorbent canister, where carbon dioxide is bound by caustic soda, and the remaining oxygen is returned to the breathing bag. The oxygen consumed by the diver is supplied to the breathing bag through a calibrated nozzle at a rate of approximately 1 - 1.5 liters per minute or is added by the diver using a manual valve. During a dive, compression of the breathing bag is compensated either by the operation of an automatic bypass valve or by a manual valve controlled by the diver himself. It should be noted that, despite the name “closed”, any closed-circuit rebreather releases breathing gas bubbles through an etching valve during ascent. To get rid of bubbles, caps made of fine mesh or foam rubber are installed on the etching valves. This simple device is very effective and reduces the diameter of the bubbles to 0.5 mm. Such bubbles completely dissolve in water after just half a meter and do not unmask the diver on the surface.

The limitations inherent in closed-cycle oxygen rebreathers are primarily due to the fact that these devices use pure oxygen, the partial pressure of which is the limiting factor in the depth of immersion. So in sports (recreational and technical) training systems this limit is 1.6 ata, which limits the depth of immersion to 6 meters in warm water with minimal physical activity. In the German Navy, this limit is 8 meters, and in the USSR Navy - 22 meters.

Closed-circuit chemical rebreather with premix

There is only one such model in the world and it is called IDA-71 ( Russian IDA71 military and naval rebreather, its further development is called IDA-85, but little is known about this rebreather). Made in USSR . The parts of this device are the same as those of oxygen rebreather closed loop, but with two differences. Firstly, there is an automatic washing machine. This mechanical device, which, when a depth of 18-20 meters is reached (it cannot be adjusted more precisely), stops the supply of pure oxygen to the breathing bag and begins supplying a mixture consisting of 40% oxygen and 60% nitrogen (that is, Nitrox). The second (and main) feature is that the IDA-71 has two chemical absorbent canisters. The first is charged with a conventional chemical absorbent based on caustic soda, and the second with an O3 (o-tri) substance created on the basis of sodium peroxide. Substance O3 is capable of not only absorbing carbon dioxide, but also releasing oxygen. The operating principle of IDA-71 is that the diver’s oxygen consumption is compensated not only by supplying fresh breathing mixture, but also by releasing oxygen with the O3 substance. Thus, there is no (at least theoretically) excess of the breathing mixture and the device does not release gas bubbles, earning the right to be called “closed”.

Since the rate of oxygen release by the O3 substance is not constant and depends on many factors that cannot be taken into account, such as, for example, water temperature, it is impossible to accurately determine the oxygen content in the breathing bag of a rebreather, but this task is not set. The diver simply must covertly complete a combat mission. The limitations for this device are inherent in its very design and, in addition to the unpredictability of the oxygen content in the breathing gas, are also due to the use of extremely dangerous substance O3. If water gets on the substance, a violent reaction begins with the release of oxygen, which, if the apparatus leaks, will mean death from oxygen poisoning at depth. Not a single country has launched a similar device into series or experimented with it due to its extreme unpredictability and danger.

To plan dives, decompression tables are used, calculated for a given device on the assumption that partial pressure oxygen 3.2 ata is quite safe.

Closed cycle rebreather with manual oxygen supply

This system is also called K.I.S.S. (Keep It Simple Stupid) and was invented by Canadian Gordon Smith. This is a closed-cycle rebreather with mixture preparation “on the fly” (selfmixer), but to the maximum simple design. The operating principle of the device is that 2 gases are used. The first, called diluent, is supplied to the breathing bag of the apparatus through an automatic bypass valve to compensate for the compression of the breathing bag during immersion. The second gas (oxygen) is supplied to the breathing bag through a calibrated nozzle with constant speed, however, less than the rate of oxygen consumption by the diver (approximately 0.8-1.0 liters per minute). When diving, the diver must himself monitor the partial pressure of oxygen in the breathing bag according to the readings of electrolytic oxygen partial pressure sensors and add the missing oxygen using a manual valve. In practice, it looks like this: before diving, the diver adds a certain amount of oxygen to the breathing bag, setting the required partial pressure of oxygen using sensors (within 0.4-0.7 ata). During the dive, a diluent gas is automatically added to the breathing bag to compensate for depth, reducing the oxygen concentration in the bag, but the partial pressure of oxygen remains relatively stable due to the increase in water column pressure. Having reached the planned depth, the diver uses a manual valve to set any partial pressure of oxygen (usually 1.3) and works on the ground, monitoring the readings of the oxygen partial pressure sensors every 10-15 minutes and adding oxygen, if necessary, to maintain the required partial pressure. Typically, within 10-15 minutes, the partial pressure of oxygen decreases by 0.2-0.5 ata, depending on physical activity.

Theoretically, not only air, but also trimix can be used as a diluent gas, which allows diving with such a device to very decent depths, however, the relative variability of the partial pressure of oxygen in the breathing circuit makes it difficult to accurately calculate decompression. Typically, such devices are used to dive no deeper than 40 meters, although there are cases of successful use of trimix as a diluent gas and diving to depths of 50-70 meters. The deepest dive with a device of this type can be considered the trick of Matthias Pfizer, who dived to 160 (one hundred and sixty) meters in Hurghada. In addition to oxygen partial pressure sensors, Mathias also used a VR-3 computer with an oxygen sensor, which monitored the partial pressure of oxygen in the mixture and calculated decompression taking into account all changes in the breathing gas. In general, everything was quite safe, but Matthias did not recommend anyone to repeat this feat. And he did the right thing.

There are a great many conversions of commercial, military and sports rebreathers to the K.I.S.S. system, but all this, of course, is unofficial and under the personal responsibility of the diver converting and using them.

Electronically controlled closed circuit rebreather

Inspiration - electronically controlled rebreather

Actually a real closed-cycle rebreather (electronically controlled selfmixer). The first such device in history was invented by Walter Starck and was called Electrolung. The principle of operation is that a diluent gas (air or Trimix or HeliOx) is supplied by a manual or automatic bypass valve to compensate for the compression of the breathing bag during diving, and oxygen is supplied using a microprocessor-controlled solenoid valve. The microprocessor interrogates 3 oxygen sensors, compares their readings and, averaging the two closest ones, issues a signal to the solenoid valve. The readings of the third sensor, which differ most from the other two, are ignored. Typically the solenoid valve is activated once every 3-6 seconds depending on the diver's oxygen consumption.

The dive looks something like this: the diver enters two oxygen partial pressure values ​​into the microprocessor, which the electronics will maintain for different stages dives. Typically this is 0.7 ata to exit from the surface to the working depth and 1.3 ata to stay at depth, undergo decompression and ascent to 3 meters. Switching is carried out using a toggle switch on the rebreather console. During the dive, the diver must monitor the operation of the microprocessor to identify possible problems with electronics and sensors.

Structurally, electronically controlled closed-cycle rebreathers have virtually no restrictions on depth, and the actual depth at which they can be used is determined mainly by the error of the oxygen sensors and the strength of the microprocessor housing. Usually the maximum depth is 150-200 meters. Electronic closed-cycle rebreathers have no other limitations. The main disadvantage of these rebreathers, which significantly limits their distribution, is high price the device itself and consumables. It is important to remember that conventional computers and decompression tables are not suitable for diving with electronic rebreathers, since the partial pressure of oxygen remains constant throughout almost the entire dive. With rebreathers of this type, either special computers (VR-3, HS Explorer) must be used, or the dive must be calculated in advance using programs such as Z-Plan or V-Planer. Both programs are free and recommended for use by manufacturers and creators of all electronic rebreathers.

Semi-closed cycle rebreathers

Semi-closed cycle rebreather with active feed

Simplified diagram of a semi-closed cycle rebreather

This is the most common type of rebreather in sport diving. The principle of its operation is that the breathing mixture EANx Nitrox is supplied into the breathing bag at a constant speed through a calibrated nozzle. The feed rate depends only on the oxygen concentration in the mixture, but does not depend on the depth of immersion and physical activity. Thus, the oxygen concentration in the breathing circuit remains constant during constant physical activity. Obviously, with this method of supplying breathing gas, excess gas appears, which is removed into the water through the etching valve. As a result, a semi-closed cycle rebreather releases several bubbles of the breathing mixture not only upon ascent, but also with each exhalation of the diver. Approximately 1/5 of the exhaled gas is released. To increase secrecy, deflector caps, similar to those used in closed-cycle oxygen rebreathers, can be installed on the bleed valves.

Depending on the oxygen concentration in the breathing mixture, EANx (Nitrox) can vary from 7 to 17 liters per minute, thus the time spent at depth when using a semi-closed cycle rebreather depends on the volume of the breathing gas cylinder. The immersion depth is limited by the partial pressure of oxygen in the breathing bag (should not exceed 1.6 ata) and the set pressure of the reducer. The fact is that the flow of gas through a calibrated nozzle has a supersonic speed, which makes it possible to keep the flow constant as long as the set pressure of the reducer exceeds the pressure environment two or more times.

Semi-closed cycle rebreather with passive feed

A very rare type of rebreather, currently represented only by the Halcyon RB-80 device, which has a safety certificate for the USA and Europe. The operating principle of the device is that from 1/7 to 1/5 of the exhaled gas is forcibly released into the water, and the volume of the breathing bag is obviously less than the volume of the diver’s lungs. Due to this, a fresh portion of breathing gas is supplied to the breathing circuit for each breath. This principle allows you to use any gases other than air as a breathing mixture and very accurately maintain the oxygen concentration in the breathing circuit, regardless of physical activity and depth. Since the supply of breathing gas is carried out only for inspiration, and not constantly, as is the case with rebreathers with active feed, then a semi-closed cycle rebreather with an active supply is limited in depth only by the partial pressure of oxygen in the breathing circuit. A significant negative point in the design of semi-closed cycle rebreathers with passive supply is that the automation is driven by breathing movements diver. Of the devices using a similar principle, the French rebreather Interspiro and the German CoRa are known. The first has not been produced since the mid-60s of the last century, and the second exists in single copies, although it is a relatively recent development.

Mechanical self mixer

A very rare design of a semi-closed cycle rebreather. The first such device was created and tested by Draeger in 1914. The principle of operation is as follows: there are 2 gases (oxygen and diluent), which are supplied through calibrated nozzles into the breathing bag, as in a semi-closed cycle rebreather with an active feed. Moreover, oxygen is supplied at a constant volumetric velocity, as in a closed rebreather with manual supply, and the diluent enters through the nozzle at a subsonic flow rate, and the amount of supplied diluent increases with increasing depth. Compensation for compression of the breathing bag is carried out by supplying diluent through an automatic bypass valve, and excess breathing mixture is released into the water in the same way as in the case of a semi-closed cycle rebreather with an active supply. Thus, only due to changes in water pressure during the dive, the parameters of the breathing mixture change, and in the direction of decreasing oxygen concentration with increasing depth. Mechanical self-mixers tend to change the oxygen concentration in the breathing bag when physical activity changes, and this is a direct consequence of the fact that their principle of operation is very similar to the principle on which semi-closed rebreathers with active feed are built.

The depth restrictions for a mechanical self-mixer are the same as for a semi-closed cycle rebreather with an active feed, with the exception that only the set pressure of the oxygen reducer must exceed the ambient pressure by 2 or more times. In terms of time, the selfmixer is mainly limited by the volume of diluent gas, the supply rate of which increases with depth. Air, Trimix and HeliOx can be used as diluent gases.

Literature

  • Andrey Yashin. Review of rebreathers. (Retrieved October 7, 2007). Permission to use the article is on the talk page.

Underwater Breathe-helping machine belongs to the field of diving technology, namely underwater breathing apparatus, and can be used during diving descents, underwater rescue operations, underwater technical work. The purpose of the utility model is to expand the possibilities of using an open-circuit underwater breathing apparatus, increase the safety of diving descents, simplify the conversion of the underwater breathing apparatus and, as a result, reduce its cost. The technical result from the use of the utility model is the mobility of the placement of the absorption cartridge and cylinders in the design of an open-circuit underwater breathing apparatus.


The utility model relates to the field of diving technology, namely underwater breathing apparatus, and can be used when carrying out diving descents, underwater rescue operations, and underwater technical work.

An open-circuit underwater breathing apparatus is known (Underwater Diver's Memo. Resource "Black Sea Swimmer's Library" http://divinginfo.narod.ru/library/Rukovodstvo_dlia_plovtsov_kmas.doc), which includes a cylinder with a locking device, a reducer that reduces the pressure of the gas mixture in balloon; the main design elements of this device are modular in nature and, as a result, can be placed in various locations necessary for specific task for underwater descents, namely, they can be placed on the back, side or chest of the diver, and can also be attached to the main breathing apparatus as a reserve. This device is accepted as the closest analogue of the claimed utility model. The disadvantage of the device is that it has a short time protective action caused by an open breathing cycle.

Known underwater closed-circuit breathing apparatus APDiving Vision (Inspiration. Closed Circuit Rebreather. User Instruction Manual. http://www.apdiving.com/, http://www.smrebreathers.ru/rebreathers/review/Inspiration_Evolution.htm), containing cylinders with shut-off devices, a reducer, a suspension system, an absorption cartridge, a housing, a valve box, breathing bags, a buoyancy compensation tank, a spare lung demand valve, and an external pressure gauge. The advantages of this device include: high physiology - a diver, breathing from this device with a moist, warm, oxygenated gas mixture, gets tired, cold and dehydrated much less than a diver in similar conditions, breathing from an open-circuit apparatus with cold, dry air; longer protective action time with comparable underwater vehicles open cycle breathing size and weight; reducing costs for carrying out descents by saving expensive gas mixtures; increasing the no-decompression limit; ensuring the possibility of conducting deep-sea autonomous diving descents; ensuring high dive secrecy necessary to perform military missions.

The disadvantage of this device is the location of the absorption cartridge and cylinders by fixing them in a rigid body, which is specified during the manufacture of the device. The rigid body makes it impossible to use cylinders with dimensions larger than those used in the standard configuration of the device. Thus, the design of the apparatus cannot be changed by the user to provide specific conditions for the diving descent.

Analysis of known patented solutions revealed the developer’s desire to increase the autonomy of the device (patent for invention No. SU 1722222 dated July 23, 1986), improve the characteristics of regenerative substances in a diving breathing apparatus (patent for invention No. RU 2225322 dated 30.08.2001), to increasing the safety of using a closed-cycle device due to the number of regenerative cartridges included in its composition (patent No. RU 2302973 dated December 31, 2002), improving control of the formation of the respiratory mixture entering the device (patent No. RU 2236983 dated 11.04. 2002), simplifying the procedure for reloading a regenerative product (patent for invention No. RU 2254263 dated 05/07/2004).

The purpose of the utility model is to expand the possibilities of using an open-circuit underwater breathing apparatus, increase the safety of diving descents, simplify the conversion of the underwater breathing apparatus and, as a result, reduce its cost.

The technical result from the use of the utility model is the mobility of the placement of the absorption cartridge and cylinders in the design of an open-circuit underwater breathing apparatus.

Also, the technical result is to provide mechanical and thermal protection for the absorption cartridge used in the design of the underwater breathing apparatus.

The problem is solved using the design of an underwater breathing apparatus of an open breathing cycle, containing a cylinder with a locking device, a reducer, characterized in that it contains an absorption cartridge, at least one, a breathing bag, a valve box, connecting hoses low pressure.

The problem is also solved by the fact that the device contains a cover for the absorption cartridge.

The problem is also solved by placing the cylinder on the cover of the absorption cartridge.

The problem is also solved by the fact that the device contains belts for fastening the cylinders, a sling, clamps that attract the sling to the cartridge body, and straps on the breathing bags.

The problem is also solved by the fact that the device contains a pulmonary valve.

The problem is also solved by the fact that the device contains a suspension system.

The problem is also solved by placing an absorption cartridge on the suspension system.

The problem is also solved by the fact that the device contains a pressure gauge.

The problem is also solved by the fact that the device contains a buoyancy compensator capacity.

The problem is also solved by placing an absorption cartridge at the location of the cylinder.

The problem is also solved by placing an absorption cartridge on the cylinder.

The problem is also solved by placing the absorption cartridge on the side of the cylinder.

Proposed utility model illustrated by the following drawings:

Fig.1 General scheme underwater breathing apparatus;

Figure 2 Underwater breathing apparatus using a cover;

Figure 3 Underwater breathing apparatus using a sling and clamps.

The underwater breathing apparatus consists of the following components and parts:

Suspension system 1, designed for mounting the apparatus components on it and attaching it to the diver’s body;

Valve box 2 with corrugated inhalation and exhalation hoses - providing the ability to breathe the gas mixture from the device, as well as atmospheric air when on the surface;

A set of breathing bags: inhalation 3 - to supply the required volume of the gas mixture during inhalation used for breathing by the diver, exhalation 4 - to collect exhaled air;

Cylinder with a shut-off device 5 or two cylinders with shut-off devices designed to hold a supply of gas mixtures;

Reducer 6 - to reduce the pressure of the respiratory mixture coming from the cylinder;

Buoyancy compensator, “wing” 7, designed to compensate for the negative buoyancy of the diver, both at the time of immersion and while on the surface;

A lung demand valve with a hose 8 - for the diver to breathe directly from the apparatus cylinder in an emergency;

Remote pressure gauge 9 - for visual monitoring of the pressure of the gas mixture in the cylinder;

Oxygen indicator 10 - for visual monitoring of oxygen partial pressure;

Absorption cartridge 11 - for cleaning exhaled gas from CO2 contained in it;

12 hoses for inhalation and exhalation of the cartridge;

T-connectors 13;

Inflator hose 14;

Inhalation bag inflating hose 15;

Exhalation bag inflator hose 16;

Gas supply hose from the reducer to the manifold 17;

Hose for supplying breathing mixture to cartridge 18;

Belts 19;

Covers 20 (for versions with a cover).

To place the absorption cartridge 11 on the diver's back, it is secured to the buoyancy compensator 7, the standard compensator straps are threaded through the loops on the side surface of the cover 20 so that the cartridge is pulled in similarly to the cylinder of an apparatus with an open breathing circuit. Unlike the latter, thanks to the presence of the cover, there is no need to attract the cartridge with a force similar to the force required to securely fasten the cylinder - thanks to the presence of loops, the absorption cartridge is securely fastened.

To fix the small-volume cylinder 5 to the absorption cartridge 11, mounted on the buoyancy compensator, straps for attaching cylinders are threaded into the loops of the absorption cartridge cover, which cover the small-volume cylinder so that the absorption cartridge remains outside the belt loop.

To secure the absorbent cartridge to a cylinder with a breathing mixture, located either on the buoyancy compensator on the diver's back or on the side suspension, straps of the same type are used as for securing the cylinder to the buoyancy compensator. To do this, the belts are threaded through the loops of the absorption cartridge cover so that they cover the cylinder to which the cartridge will be attached, and the cartridge itself remains outside the belt loop.

To directly secure the absorption cartridge on the side suspension, carabiners are tied to the loops of the cover using ropes, which are attached to the buoyancy compensator attachment points.

The absorbent cartridge case consists of a fabric bag, the dimensions of which exactly correspond to the dimensions of the absorbent cartridge and elements that ensure its docking with other elements of equipment. The neck of the bag, through which the cartridge is inserted inside, has a tightening device consisting of a rope and a clamp. To securely fix the cartridge inside the case, the neck of the case also has straps with locks.

For fastening to other elements of equipment, the cover of the absorption cartridge has loops made of slings on the side and bottom end surfaces (the bottom of the “bag”).

To transfer the device from an open cycle to a closed or semi-closed breathing cycle, without using a special cover in the design of the device, three steel clamps are located on the absorption cartridge 11, attracting the sling to the cartridge body, so that it forms two loops into which there can be The cylinder fastening straps are threaded. On the covers of the breathing bags 3 there are several pairs of straps with fastenings for encircling the shoulder straps of the suspension system of the open-circuit apparatus. A sling with fastex buckles ensures tight fixation of the breathing bags on the diver’s body.

The absorption cartridge is attached to the apparatus in two ways:

Installing the cartridge on the side of the back balloon. This is achieved by threading the balloon belts of the suspension system into the loops on the absorption cartridge;

Installing the cartridge in place of the back balloon. In this case, the cylinder belts are also threaded through the loops, but the belts cover the cartridge, similar to how this is done when installing a cylinder.

The technical solution proposed as a utility model, used in the design of an underwater breathing apparatus, allows the absorbent cartridge of the apparatus to be placed in various places equipment, namely:

On the diver’s back, by fixing it on the buoyancy compensator;

On the diver’s back or on a side sling, when fixed to a cylinder with a breathing mixture;

On the side of the diver, by attaching the buoyancy compensator directly to the mounting components of the suspension system.

In addition, when using lightweight fabric materials, the solution makes it possible to attach small-volume cylinders directly to the cover of the absorption cartridge, reducing the size and weight of the connecting unit of the device, and providing mechanical and thermal protection of the absorption cartridge.

The ability to convert open-cycle devices to closed and semi-closed cycles increases the protective action time of the device, while to perform simple tasks it is possible to transfer the device back to open-cycle operation by removing the expansion module.

Breathing apparatus manufactured by JSC KAMPO were manufactured and put into operation, in which the technical solution claimed as a utility model is implemented. The device can be manufactured in serial machine-building production using general-purpose equipment without additional capital investments.


Utility model formula

1. An underwater open-circuit breathing apparatus containing a cylinder with a shut-off device, a reducer, characterized in that it contains an absorption cartridge, at least one breathing bag, a valve box, and low-pressure connecting hoses.

2. The device according to claim 1, characterized in that it contains a cover for the absorption cartridge.

3. The device according to claim 2, characterized in that the cylinder is placed on the cover of the absorption cartridge.

4. The device according to claim 1, characterized in that it contains belts for fastening cylinders, a sling, clamps that attract the sling to the cartridge body, straps on breathing bags.

5. The device according to claim 1, characterized in that it contains a buoyancy compensator tank.

6. The device according to claim 1, characterized in that it contains a lung demand valve.

7. The device according to claim 1, characterized in that it contains a suspension system.

8. The device according to claim 7, characterized in that the absorption cartridge is placed on the suspension system.

9. The device according to claim 1, characterized in that it contains a pressure gauge.

10. The device according to claim 1, characterized in that the absorption cartridge is placed on the cylinder.

11. The device according to claim 1, characterized in that the absorption cartridge is placed at the location of the cylinder.

12. The device according to claim 1, characterized in that the absorption cartridge is located on the side of the cylinder.

If we consider technical diving
like the pinnacle of scuba diving,
then rebreathers are just a complete flight into space!

Few people know that rebreathers or closed-circuit breathing apparatus came to us much earlier than conventional scuba gear, for this you just need to look into the history of the invention of the rebreather and nevertheless, only in our time has technological progress helped to make these dives on closed-circuit systems universally available to the diving community, and not just to professionals from specialized military and scientific organizations.

You are pretty tired of the roar of exhaled air, and a pile of heavy iron with the outlines of hung cylinders does not look as aesthetically pleasing as the first time, and of course you have long wanted to optimize your decompression regime, then the path to rebreathers is your way!

as follows:


It is considered the most successful and therefore the most widespread semi-closed cycle rebreather with passive supply of respiratory mixture.

Developed by the German company Draeger and is a modification of the earlier Atlantis I model. This model is easy to operate and reliable in use.

Using standard nitrox mixtures, it allows diving to a depth of 40 meters. There is a modification using trimix, which increases the permitted depth to 80m.

Training to operate this device takes 2–3 days. Four open water dives allow you to fully practice the necessary exercises and gain a complete understanding of the specifics of diving in a rebreather. We highly recommend this course as a pre-course to the Inspiration course.


This is the world's first mass-produced closed-loop mixture rebreather. In addition, Inspiration is the first and, to date, the only device in its class to receive certification from the European Standardization Agency. This certificate authorizes safe use apparatus at depths of up to 50 meters with air as a diluent and at least up to 100 meters using trimix mixtures.

gives us the opportunity to use all the advantages of nitrox mixtures, and at 100%. The control unit automatically maintains a constant partial pressure of oxygen in the breathing circuit, regardless of depth, accordingly constantly changing the percentage composition of the mixture. In other words, the device provides the optimal breathing mixture (best mix) at any depth throughout the dive, right up to the supply of pure oxygen at the last decompression stops.

This means unprecedented versatility: whether it's a deep-water wreck or a shallow coastal reef, it makes no difference - a standardly prepared apparatus will provide you with the optimal mixture at any depth. It allows you to fully realize all the advantages of best mix, such as expanding NDL, minimizing decompression modes, etc., but without the tedious preliminary planning associated with selecting a gas mixture depending on the specific dive depth, calculating gas reserves, and selecting equipment configuration , stage cylinders, etc. In addition, you are spared the hassle of switching from mixture to mixture underwater.

Diving with Inspiration means making the most of gases. This efficiency is especially pronounced at significant depths, where the consumption of the gas mixture in systems operating according to an open breathing scheme becomes catastrophic. Hence the high popularity of the rebreather among technical divers.

Along with the already listed advantages, the following should be noted: positive traits such as minimizing the cost of expensive helium, the compactness of the apparatus, the ease of buoyancy control, breathing with warm humidified gas and, finally, the complete absence of exhaled bubbles, which makes the dive comfortable, quiet and does not cause stress in underwater inhabitants.

Inspiration revolutionized diving. Being the first mass-produced device of this class and, most importantly, affordable, it is widely sold in more than 40 countries around the world. Having passed rigorous tests in specialized organizations in the UK and the USA, the device is manufactured in strict accordance with standards and quality requirements, and is provided with after-sales service and a factory supply of spare parts.

- The exhaled gas is directed by a non-return valve through a hose into the exhalation bag. This is where the cycle begins.
- Then the gas, freed from possible residual water, enters the absorber cartridge. Here it enters into a chemical reaction with an absorbent (Sofnolime), where it is released from carbon dioxide.
- In the mixing zone at the top of the cartridge there are three independent oxygen sensors that measure the partial pressure of oxygen in the mixture, allowing the electronic regulator to accurately maintain the set PO2 value by injecting additional amounts of pure oxygen from the cylinder as it is consumed by the body.
- The purified and oxygen-enriched mixture passes through the hose into the inhalation bag, and then through the valve box to the mouthpiece. The cycle is complete.

Diluent

Inspiration has two three-liter cylinders. One cylinder contains pure oxygen, the other contains the so-called diluent - a diluent gas. Up to a depth of 50 m it is usually air, deeper - trimix or heliox. Diluent has several functions:

Manually or through a pulmonary valve (if installed), diluent is supplied to the breathing circuit to compensate for the pressure increasing with increasing depth and to prevent the “collapse” of the bags.

It is also used for BCD and drysuit inflation. The diluent consumption is extremely insignificant, about 30 - 40 bar for the entire dive.

As a diluent, it is the main component of the respiratory gas mixture, maintaining it within safe limits from the point of view of oxygen poisoning.

One of the most important functions of diluent is the ability to use it as a reserve supply for circuit ventilation or to switch to open circuit breathing in the event of an emergency.

Growing popularity.

Modern open-circuit breathing apparatus, or conventional scuba gear, began to be actively used after 1943, when they were invented by Jacques Cousteau and Emile Galliano. Closed-loop devices for a long time remained unclaimed.

In 1987, as part of the Wakulla springs project, under the leadership of Doctor of Sciences William Stone, while exploring a cave system 5 km long, the CisLunar Mark I was tested, a closed-type apparatus that demonstrated certain advantages over scuba gear. Since then, interest in this species breathing apparatus began to increase.

Rebreathers and their main types
Closed-type breathing apparatus are usually called rebreathers, from English word“rebreather”, that is, “rebreather”. The spent breathing gas in them is not discharged into the water, but, freed from carbon dioxide, is enriched with oxygen, and then supplied again for breathing. Therefore, rebreathers are more complex than scuba gear.

In addition to the hose connecting the cylinder to the mouthpiece, there is a second one to return the spent mixture to the circuit. There must be a semi-rigid or soft bag with a water trap to receive the exhaled mixture, the pressure of which must be equal to the external water pressure. Next, the mixture is fed into a canister, in which carbon dioxide is removed from it by a chemical absorber. The subsequent addition of oxygen is carried out in each type of apparatus in its own way.

The main criterion for classifying rebreathers is the degree of isolation respiratory cycle. There are completely closed-cycle devices, or CCR rebreathers, in which the exhaled mixture is completely recycled. The gas in them is released into the water, but only upon ascent, through the release valve. The decreasing pressure causes the mixture to expand, so its excess is removed.

Semi-closed devices, called SCR rebreathers, use artificial breathing mixtures (Trimix, Nitrox, Heliox), rather than pure oxygen, so the excess nitrogen and helium that appears must be periodically removed from the breathing circuit.

Closed circuit rebreathers

The design of a rebreather operating on pure oxygen is the simplest and lightest; the device does not leave bubbles in the water, therefore it is popular among biologists and the military. However, the use of oxygen alone introduces limitations. As pressure increases, it becomes toxic, negatively affecting the respiratory and nervous system. In this regard, the depth for diving should not exceed 7-10 m. Oxygen, moreover, contributes to the rapid development of caries.

One of the types of oxygen rebreather is a device with chemical regeneration of the breathing mixture. In the absorption canister, a volume of oxygen is released equal to the absorbed carbon dioxide, which allows you to stay under water record number time - up to 6 hours. Due to the danger of the regenerating substance, which releases alkali when water gets into it, such devices are almost never used.

There are rebreathers that allow you to work with artificial breathing mixtures, which allows you to dive to fairly great depths. Some devices use an electronic system to control the supply of oxygen to the breathing circuit, the weak point of which is electrochemical sensors that require regular replacement, and an electromagnetic valve. Famous representatives- CIS Lunar, Buddy Inspiration. In others, the control is semi-automatic, where the oxygen supply is controlled by the diver.

Semi-closed rebreathers

The difference in the design of semi-closed cycle rebreathers lies in the way the breathing mixture is supplied. In devices with active supply, when the valve on the cylinder is opened, the breathing mixture is continuously fed into the breathing circuit through a nozzle with throughput, changing with depth and depending on the mixture used. Such rebreathers are simple in design and maintenance; it is easy to calculate a dive plan with them, since the mixture consumption at any depth is approximately the same. Perhaps that is why they have gained the greatest popularity among other types of rebreathers. Famous devices of this type are Ray and Draeger Dolphin, Atlantis and Azimuth.

In devices with passive supply of the mixture, the amount of gas removed and supplied is not regulated depending on the pressure, that is, on the depth, so the flow rate of the gas mixture must be calculated as for a conventional scuba tank. But a rebreather, unlike a scuba tank, has several times more time under water, since it does not release the entire volume of exhaled gas, but approximately 10 to 30 percent. Well-known devices of this type are the Halcyon RB-80 (the analogue is the European RB2000).

Rebreather or scuba gear?

Rebreathers outperform conventional scuba gear with less noise and fewer bubbles, constant buoyancy when inhaling and exhaling, since the volume of the mixture does not decrease, or almost does not decrease, when exhaling. The absorption of carbon dioxide releases moisture and heat, which makes the air a diver inhales more pleasant, thereby increasing resistance to decompression sickness. In addition, the time spent under water with a rebreather increases, and the delivery of gas mixtures to the dive site does not cause so much trouble by reducing their required volume. Closed-cycle rebreathers using mixtures make it possible to reach greater depths than the threshold 40 m for other devices.

Why haven't rebreathers replaced conventional scuba gear? They have their drawbacks. These devices are more expensive, more difficult to maintain, have greater weight and size, they are inconvenient for use by two divers in critical situations, and require maintenance consumables, such as an absorber and various sensors. In addition, the rebreather is more convenient to use in a team.

As you can see, the advantages of each type of breathing apparatus are balanced by its disadvantages, therefore both rebreathers and scuba tanks are worthy of finding their application. When choosing, you should clearly know what the device will be used for, what type of devices are used in the team. Choosing a rebreather will not make you disappointed in it. It’s not in vain that they begin to conquer Lately popularity in Russia

based on materials from the site aqua-globus.ru

Forces Command special operations Russian Federation received new double-medium breathing apparatus, the so-called rebreathers. Journalists from the newspaper "" write about this. Thanks to the new devices, the Russian military will be able to breathe both when diving to a depth of up to 20 meters, and during long parachute jumps from a height of 8-10 thousand meters above sea level. According to experts, universal breathing devices that could work both underwater and in rarefied air existed only in two countries - the USA and Germany (Seals Team No. 6 and the German Kommando Spezialkräfte, respectively). Now Russia will be added to these two states. Thanks to the new double-medium breathing apparatus, the operational and tactical capabilities of the soldiers of the Russian Special Operations Forces Command will increase significantly.

Until recently, all Russian special forces soldiers had to wear special apparatus for breathing on high altitude, as well as scuba gear. After landing on the water, the special forces changed masks and switched the supply of breathing gas before diving. With the advent of the new DA-21Mk2D rebreather, the need to switch the supply of the breathing mixture has disappeared. In addition, thanks to the new breathing apparatus, the composition of the equipment of Russian fighters can be reduced. The new double-medium breathing apparatus was designed jointly by the St. Petersburg State Marine technical university(SPbGMTU) and Ryazan High Airborne command school(RVVDKU).


The weight of the DA-21Mk2D device is approximately 10 kilograms. It is designed for normal operation at ambient temperatures from -2 to +30 degrees Celsius. The reziber contains enough breathing mixture for continuous operation for four hours. The new double-medium breathing apparatus is a closed-circuit breathing apparatus. DA-21Mk2D was equipped with a special capsule with calcium hydroxide. It is through this that the air exhaled by a special forces soldier passes through. Calcium hydroxide absorbs carbon dioxide from exhaled air to form calcium carbonate. Then the air, cleared of carbon dioxide, is enriched with oxygen and again enters the fighter’s breathing mask.

Dummy with rebreather DA-21Mk2D Source: Oceanos

The first rebreather in the Soviet Union, designed specifically for parachutists, appeared in the first half of the 1970s. The device received the designation IDA-71P. This device is designed to perform water jumps from a low height, at which special forces can do without an oxygen mask. Nowadays, the IDA-71P is in service with reconnaissance divers and combat swimmers. The device belongs to the regenerative type; in this breathing apparatus, in addition to the usual carbon dioxide absorber, a special regenerative substance based on sodium peroxide is also used. This substance not only successfully absorbs carbon dioxide, but also releases oxygen, which is then mixed into the purified air. The implementation of such a scheme allows you to reduce the consumption of oxygen from the cylinder.

Tests of the new DA-21Mk2D breathing apparatus should take place in the summer of 2017 in Crimea. They are planned to be carried out at the training center of the Special Operations Forces (SSO), Izvestia reports, citing representatives of the Russian military department familiar with the test plans. Currently, the new double-medium respiratory system It is already undergoing underwater tests, which are scheduled to be completed at the end of 2016 - beginning of 2017. After this, the system will be tested at an altitude of 10 thousand meters. Directly in Crimea, the command of special operations forces will be engaged in a comprehensive check of the device, including long parachute jumps into the water.

According to Alexey Blinkov, head of the department of defense research and development, the unique double-medium breathing system was developed on the basis of the DA-21Mk2 complex, which is already in service Russian fleet. IN new version the device, which received the prefix “D” (“landed”), was significantly modified. So, according to the requirements of the military, the mounting of the device was moved to the chest. This is done so that the paratrooper can carry a double-medium breathing apparatus along with a parachute pack. The device was also significantly lightened, its weight was reduced by more than half - from 21 to 10 kilograms due to the use of modern composite materials and refusal to supply a nitrogen-oxygen mixture in favor of ordinary oxygen. According to Alexey Blinkov, special forces perform tasks underwater at a depth of up to 20 meters. In this regard, after consultations with the military, we decided not to use a nitrogen-oxygen mixture, which is not intended for breathing at high altitudes.

Under normal conditions, combat swimmers are delivered to the site of sabotage on submarines and ships, notes military expert Vladislav Shurygin. - However, in the presence of sonar barriers, modern coastal defense radar stations and patrols, penetrate into the desired area traditional way Underwater saboteurs do not always succeed. It is for this reason that today a system has developed in the world where special forces soldiers make long high-altitude jumps landing in the water, and only then begin to solve the tasks assigned to them, including going ashore.

It must be remembered that the equipment used by combat swimmers today is seriously different from the cylinders with which all people familiar with diving are familiar with compressed air and oxygen. Such containers would take up a lot of space on the human body. In addition, they have a rather unpleasant factor - the air that is exhaled from the lungs enters the water through the valves in the form of bubbles, which unmask the swimmer. At the same time, closed-cycle devices (rebreathers) are much more compact, and their operation is based on a different principle - oxygen is not stored in a separate container, it is generated using chemical reaction. At the moment of exhalation, the air from the swimmer’s lungs, in which the carbon dioxide content is increased, and the oxygen content, on the contrary, is decreased, is sent to a special container in which there is a regenerating element, which absorbs carbon dioxide. Subsequently, the oxygen-enriched mixture again enters the inhalation channel. The device is able to provide the ability to breathe underwater for several hours, and this time period is calculated taking into account the fact that the special forces soldier will be actively moving, while consuming significantly more oxygen.

In addition to compactness, all rebreathers have one more important advantage: closed-cycle devices emit almost no bubbles into the water. Of course, some of the swimmer’s exhalation is released through a special valve, but these are such small volumes that there are no air bubbles on the surface of the water that could unmask a special forces soldier and disrupt the execution of a combat mission.

Information sources:
http://izvestia.ru/news/639512
https://nplus1.ru/news/2016/10/24/rebreather
http://www.utro.ru/articles/2016/10/25/1302166.shtml