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Lambertsen Amphibious Respiratory Unit (LARU)

What is the Lambertsen Amphibious Respiratory Unit (LARU)?

The Lambertsen Amphibious Respiratory Unit (LARU) is a type of rebreathing device designed for military and commercial underwater applications. It was developed by Dr. Christian J. Lambertsen, during World War II, for use by the United States Office of Strategic Services. The LARU allows a diver to breathe underwater for extended periods without leaving a trail of bubbles, which could alert enemy forces.

Who is Dr. Christian J. Lambertsen and what led him to develop the LARU?

Dr. Christian J. Lambertsen was an American scientist and inventor. During World War II, recognizing the strategic advantage of underwater operations, he developed the LARU for covert military purposes, essentially inventing the modern discipline of military/commercial diving.


How does the LARU work?

The LARU is a closed-circuit rebreather, which means that it recycles exhaled air, removing carbon dioxide and adding oxygen as needed. Unlike open circuit systems that release exhaled air into the water, the LARU conserves gas, allows longer dive times and does not leave a trail of bubbles.

What are the components of LARU and their functions?

The LARU consists mainly of three components: the breathing bag, the absorbent canister, and the oxygen supply. The breathing bag holds the gas for breathing, the absorbent canister filters out carbon dioxide from exhaled gas and the oxygen supply replenishes oxygen that was consumed by the diver.


What advantages does the LARU have over traditional scuba gear?

The primary advantage of the LARU is stealth, as it does not emit bubbles, which are visible and noisy underwater. It also allows for longer dive times due to its efficient use of oxygen. Moreover, because it doesn't release bubbles, it reduces the risk of decompression sickness or "the bends".

What is decompression sickness and how does the LARU reduce the risk?

Decompression sickness, also known as "the bends", is a condition that can occur when a diver ascends too quickly causing nitrogen bubbles to form in the bloodstream. Because the LARU recycles gases and slowly releases excess, the nitrogen build up is reduced, thus reducing the risk of decompression sickness.


How is the LARU maintained?

Maintenance of the LARU involves regularly checking and replacing the absorbent canister which removes carbon dioxide. Moreover, the breathing bag and the oxygen supply need to be inspected and serviced to ensure they are functioning properly. All connections must be checked for leaks as well.

What are potential signs that a LARU needs maintenance or repair?

Signs that a LARU needs maintenance include difficulty breathing, presence of moisture in the breathing bag, a decrease in oxygen levels or any visible damage or leakage. Regular inspection and maintenance can prevent many of these issues.


What training is required to use a LARU?

Due to inherent risks and technical complexities, rigorous training is required to use a LARU. This includes understanding how the equipment works, how to maintain it, how to handle emergencies, understanding diving physiology, and building the necessary diving skills.

Where can someone receive training to use a LARU and what does the training typically involve?

Training can be acquired through certified diving schools that offer advanced and technical diving courses. This training typically involves classroom time, practice in controlled environments like swimming pools, and finally open-water dives under the supervision of a certified instructor.


Why did the navy view the development of the LARU as important?

The Navy saw the LARU as a crucial tool for covert operations as it allowed divers to remain undetected due to the absence of bubbles. Its extended duration under water also gave a strategic advantage, as it allowed for longer, more in-depth operations.

Can you provide an example of a military operation where the LARU was used?

Though many operations remain classified, the LARU is known to have been used in numerous covert operations such as underwater demolitions and reconnaissance missions during World War II.


Are there any limitations or disadvantages associated with using a LARU?

While the LARU has many advantages, it also has some limitations. It can be technically complex and requires a high level of training to operate safely. Also, the gas mix in a LARU must be carefully managed to avoid hypoxia or oxygen toxicity.

Can you explain what hypoxia and oxygen toxicity are?

Hypoxia occurs when there is an insufficient amount of oxygen for the body's needs, which can result in unconsciousness or death. Oxygen toxicity, on the other hand, is caused by exposure to excessive oxygen levels, leading to lung or central nervous system damage.


What are the safety protocols divers must follow when using a LARU?

Divers using LARU must always check their equipment before use, ascend and descend slowly to prevent decompression sickness, constantly monitor their gas mixture to avoid hypoxia or oxygen toxicity, and always dive with a buddy for redundancy and emergency response.

How does the buddy system enhance safety when using the LARU?

The buddy system ensures there is another person who can provide assistance in the event of equipment failure, unexpected health issues, or other emergencies. It provides redundancy and a quick response in the underwater environment where surfacing immediately can be dangerous.


Can the LARU be used for any type of underwater activity?

The LARU is primarily designed for military, research, and commercial divers. Its complex nature and specialized training requirements make it less suitable for recreational divers. However, it can be used in any situation where extended, stealthy underwater operations are required.

How might a marine biologist or underwater archaeologist utilize the LARU?

A marine biologist or underwater archaeologist might use the LARU for long-term underwater observations or delicate excavation work, where the absence of bubbles can significantly reduce disturbance to the environment, and extended dive times enable detailed exploration.


What are some advancements or improvements made to the LARU since its original invention?

Since the original LARU, advancements have been made in almost every aspect of its design. Today's units are lighter, more comfortable, and more efficient. Oxygen level monitoring and carbon dioxide removal technology have improved. Digital controls and wearable tech have also enhanced functionality and safety.

How does wearable tech work with the LARU to enhance functionality and safety?

Wearable tech may include a dive computer which constantly calculates and displays information like depth, dive time, and gas mix, helping to manage decompression and prevent hypoxia or oxygen toxicity. It may also include alarms for immediate feedback on potential issues.