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How Air Scuba System Recycles Air Under Water

Scuba divers who use the conventional scuba systems must be very careful to monitor the depth and time while they stay underwater. They have to endure a series of lengthy decompression steps during resurfacing. But the thing is, the oxygen tank that scuba divers take with them under water is filled with limited oxygen. Before the oxygen finishes, the divers have to come up. Therefore, recycling air devices have been made at different times in order to stay more longer with shorter decompression under water. Let’s have a look into the recycling air scuba system.


The whole thing depends on the infrastructure of Air Scuba System and its air cycling process. Here I’m going to represent each single thing with details.

The Essentials

Human lungs absorb only 5% of the oxygen present in air. Rebreathers remove the carbon dioxide from exhaled air and recycle and supplement the leftover oxygen and inert gases, such as nitrogen, back into the diver’s next breath.

–> Exhale

A diver’s CO2-rich exhalation flows through a one-way valve, called a mushroom valve because of its shape, on the right side of the mouthpiece and travels down a hose.

–> Oxygenate

Before the exhaled breath enters the main part of the rebreather, an electrical valve called a solenoid regulates the flow of gas from the oxygen cylinder based on oxygen-concentration data from an onboard computer. The oxygen mixes with the CO2-rich exhalations.

–> Scrub

Next, the air enters the CO2 filter, a canister the size of a coffee can that holds about five pounds of absorbent granulated soda lime. Lime binds to the CO2 that flows through the filter but has no effect on oxygen or inert gases, allowing them to pass through unhindered.

–> Monitor

After the scrubbed air leaves the CO2 filter, three oxygen sensors and a CO2 sensor monitor the gas’s chemical composition. Too little oxygen, and the rebreather’s computer tells the solenoid valve fed by the oxygen cylinder to open; too much, and the computer tells the solenoid to close.

–> Inhale

When the diver draws his next breath, he also draws the oxygen-enriched air into the counterlung, a flexible storage bladder. Near the counterlung, a mechanical valve senses if there’s sufficient air pressure for the diver to inhale the next breath. If the pressure is insufficient, the valve opens and an oxygen-nitrogen mixture from the diluent cylinder provides enough gas to pressurize the counterlung. When the diver inhales, he pulls the freshly mixed air from the counterlung through a one-way mushroom valve on the left side of the mouthpiece and into his lungs.

Fail-Safes

Two computer handsets strapped to the diver’s forearms and a head-up display placed in his line of sight show his oxygen and carbon dioxide levels in real time. If the rebreather malfunctions, the onboard computer instructs a motor to vibrate the mouthpiece, and red lights embedded in the mask flash near the diver’s right eye. A gas-bypass button hangs from each shoulder. The diver can add oxygen or diluent manually if the automated system malfunctions. If all else fails, divers also carry a bailout scuba tank.

Sentinel

Weight 88 pound
Max. Depth 330 feet
Max. time underwater 2 hour and 45 minute at 330 feet
Number of safety steps required before dive 20
Concept completion time from now 10+ years

The Navy has already used the devices. But they found, these devices were very expensive and difficult to maintain and operate. After that, in 2008, Virtual Reality (VR) Technology introduced the Sentinel. Sentinel had automated safety systems and full manual backup and its price was a $12,000. Though scientists from Woods Hole Oceanographic Institution in Massachusetts and the National Museum of China in Beijing are using it, but this upcoming July, Hollis Gear is going to release the VR-designed Explorer which costs only $5,400.

Hope so, this new developing air recycling system would be a great use to the scuba divers in future.

Source : PopSci

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