How does Hydroid Aquabreather work?

Aquabreather is a personal breathing apparatus with a fully closed circuit. 

It is designed as an electronic Chemical Closed Circuit Rebreather – eCCCR.

It consists of a full-face mask connected in series with a reactor for regenerative cartridges and two counterlungs with a total volume of 5.2 litres (0.18 cf). A built-in 0.3 litre (18 ci) cylinder with a working pressure of 310 bar (4500 psi) is provided to equalize the volume of the breathing loop during diving.

In the visor of the helmet, a computer decompression meter is installed, displaying the main parameters of the dive and the breathing gas. This computer's only function is to present information.

How does breathing through the apparatus work?

CO2 takes up 3%-4% of a person's exhalation, О2 – 4% of an inhalation. Therefore, breathing normally with an intensity of 12 l/min (0.42 cf/min), a person exhales 0.36-0.48 l (22-29 ci) of CO2 and inhales 0.48 l (29 ci) of O2 every minute. And this does not depend on the depth.

Two regenerative cartridges contain 560 grams (1⅟4 lbs) of a regenerative substance that converts CO2 to O2. And the volume of О2 produced is up 25% from the volume of СО2 absorbed. When you are breathing, CO2 is being absorbed and O2 is being produced. If you hold your breath, the reaction will not proceed. O2 is not being supplied continuously.

The regenerative substance has the capacity to absorb 80 l/kg (1.27 cf/lb) of СО2 and produce 100 l/kg (1.6 cf/lb) of O2.

Therefore, when breathing normally, with this apparatus a diver can breathe for at least 100 minutes. Beginners breathe more intensely, approximately 18-22 l/min (0.64-0.78 cf/min). Two cartridges will last at least 1 hour.

How do I equalize the volume of the breathing loop during diving?

To equalize the volume of the loop at depth [6 litres (0.21 cf) of gas every 10 metres (30 ft)], a composite cylinder with a volume of 0.3 litres (18 ci) and a working pressure of 310 bar (4500 psi) is used. The cylinder can hold up to 100 litres (3.53 cf) of gas.

For example, to dive to a depth of 30 metres (100 ft), you will need only 18 litres (0.64 cf) of gas. The remaining 82 litres (2.9 cf) will substitute for the aluminium Air Spare cylinder with a volume of 0.42 litres (26 ci).

A 3-stage regulator is connected to the cylinder to supply gas to the loop. During diving, you can draw gas from the regulator if needed or supply it forcefully by pressing the regulator button. In closed circuit mode, the regulator is roughened at 0.03 bar. If you want to switch to the open circuit mode, you just need to turn the switch, and the regulator will be supplying gas on demand.

How do I equalize the pressure in my ears?

The mask has a special nose block. You just need to press your mask tightly to your face and then equalize the pressure in your ears.

How is the loop protected against water ingress? How is water removed from the mask?

At the bottom of the mask, there is an isolating float valve and a draining valve. If the water leaks into the mask, the float will close the loop. When you exhale, the water will be automatically removed through the draining valve. In addition to the float and isolating valves at the bottom of the mask, the loop is protected by another isolating valve at the top. If the apparatus is taken off completely when under water, the mask will be cleaned by forced gas supply from the cylinder.

How hot are the cartridges?

During the reaction, the temperature of the regenerative substance can reach 150°C (302°F), but the circulating gas can only be heated up to 38°C (100°F).

Are the cartridges with regenerative substance protected against water ingress?

The cartridges are equipped with moisture-proof membranes.

If water does get into the cartridges, can they explode?

If water enters the regenerative substance, the substance will not explode, but its granules will begin to swell, preventing the gas from circulation. In this case, you have to switch to the open circuit and rise to the surface.

What should I do if the cartridges stop working abruptly?

The reaction in the cartridges completely stops after 5-8 minutes.
You have to switch to the open circuit mode using the built-in cylinder or bail-out.

How do I connect a bail-out to the apparatus?

The cylinder of any volume can be connected to the gas filling nozzle in the ‘chin’ of Aquabreather via a quick-release connector. The additional cylinder can be connected under water.

How do I prevent the mask from fogging?

The regeneration reaction absorbs moisture. When you inhale, the dehumidified gas passes along the glass of the mask. So there is no fogging. You can also use Antifog in addition to that.

What happens if the computer crashes?

The computer does not control the regeneration reaction. So in this case, you just need to calmly start rising to the surface.

Is it possible to lose consciousness from oxygen starvation without even noticing it?

When the regeneration reaction ends, the first thing to happen is that CO2 level in the loop slowly starts to rise. The computer will warn you that you need to finish your dive 3-5 minutes early. But you will be able to feel it even with the computer turned off. In this case, you just need to switch to the open circuit mode and rise to the surface.

Is there a possibility of oxygen poisoning during the dive?

The O2 content in the circuit grows slowly. For example, at the depth of 30 meters (100 ft), the partial pressure of O2 will not exceed 1.4 bar. When diving deeper, the no-decompression time will run out before ррО2 exceeds the permissible limits.

If ррО2 exceeds the limit, the computer will notify you about it and will suggest to rise a bit higher or to add some normoxic gas to the loop from the built-in cylinder.

How often do I need to change the O2 and CO2 sensors?

The sensors operate in a dry loop and are not subject to high humidity. The service life of the O2 sensor is at least 3 years, CO2 sensor – 10 years.

How do I deal with nitrogen narcosis?

Just as with any other scuba set. You only need to dive to a depth where you don't experience nitrogen narcosis.

But Aquabreather has a big advantage.  Due to the rising O2 level, you start the dive in the air and finish at EAN 36-40. This way, the nitrogen content in the breathing loop is constantly reducing, and the no-decompression limits are almost doubled.

Does the apparatus work in cold water?

Yes, Aquabreather can work in cold water. The regeneration reaction is stable at -30°C (-22°F), and the counterlungs are made of polyurethane that does not harden in the cold.

How do I maintain neutral buoyancy?

THE HUMAN LUNGS-APPARATUS CIRCUIT SYSTEM has a constant volume. Your breathing during a dive does not affect buoyancy. It remains unchanged. You only need to take enough ballast to have a neutral buoyancy at the surface of the water.

Do I need a buoyancy compensator?

No, you don't. You'll only need Aquabreather, a weight belt, fins, and a diving suit.

Where do I get gas for a dry suit?

For a dry suit you will need an additional mini-cylinder with a volume of 0.2-0.8 litres (13-48 ci). You can use argon.

What maintenance does the apparatus require?

After diving in seawater, the apparatus must be desalinated from salt. The cylinder needs to be verified every 5 years. How often you will need to replace sensors depends on how often and how deep you dive.

What gas do I fill the cylinder with and how do I do it?

For recreational diving, the cylinder can be filled with air or normoxic heliox through a nozzle in the ‘chin’ of the apparatus.

You can fill it using:

  • stationary high-pressure compressor,
  • 12V high-pressure mini compressor,
  • high-pressure manual pump [we recommend up to 100 bar (1450 psi)],
  • another gas cylinder.