Which of the following gas mixture is used by the divers inside the sea? (a) \(\mathrm{O}_{2}+\mathrm{Ar}\) (b) \(\mathrm{O}_{2}+\mathrm{He}\) (c) \(\mathrm{O}_{2}+\mathrm{Xe}\) (d) \(\mathrm{O}_{2}+\mathrm{N}_{2}\)

Imagine diving in deep blue waters when suddenly you feel a bit tipsy, similar to having a few drinks too many. This phenomenon, known as nitrogen narcosis, can occur to divers who descend beyond certain depths. The effect is due to the increased partial pressure of nitrogen at depth, which causes nitrogen molecules to have a narcotic effect on the brain, impairing cognitive and motor functions.

Divers call it 'the rapture of the deep,' which can be quite dangerous as it affects decision-making and the diver's ability to respond to potential hazards. To minimize this risk, deep-sea divers often use gas mixtures like oxygen and helium instead of nitrogen. Helium, being inert and not having the narcotic properties of nitrogen, provides a safer alternative for breathing underwater at high pressures.

Preventing Nitrogen Narcosis

• Using gas mixtures without nitrogen (e.g., trimix or heliox)
• Limiting the depth and duration of dives
• Acclimatization to increased pressure through gradual descent

The benefit and necessity of oxygen for sustaining life is unquestionable. However, in the peculiar environment of deep-sea diving, too much oxygen can become perilous. Oxygen toxicity occurs when the body is exposed to high partial pressures of oxygen, which can result in cell damage and a variety of symptoms that range from tunnel vision and ear ringing to seizures and lung damage.

As divers go deeper under the sea, the concentration of oxygen in their gas mixture needs careful adjustment to avoid this toxicity. By using a blend of gases such as helium and oxygen—known as heliox—divers can reduce the risk of oxygen poisoning while ensuring they can still breathe effectively. It's about striking the right balance: enough oxygen to support metabolism, but not so much as to be toxic.

Strategies for Avoiding Oxygen Toxicity

• Controlling the oxygen partial pressure by adjusting the gas mix
• Using special dive computers to monitor exposure levels
• Limiting the time spent at depths where oxygen toxicity risk increases

The gas mixture in a diver's tank is a critical factor in ensuring safety and performance under the sea. The unique pressures encountered during deep-sea diving necessitate a careful choice of deep-sea diving gases. The ideal mixture includes a balance of gases that minimizes the risks of nitrogen narcosis and oxygen toxicity while allowing the diver to breathe comfortably.

Oxygen and helium (heliox) is a popular mixture due to helium's inertness and non-narcotic quality under pressure. It also has a lower density than nitrogen, enabling easier breathing. In addition to heliox, other mixtures like trimix (oxygen, nitrogen, and helium) and hydrox (hydrogen and oxygen) are sometimes used depending on the depth and duration of the dive.

Key Properties of Diving Gases

• Non-narcotic under pressure
• Appropriate oxygen concentration to avoid toxicity
• Low density for easier breathing
• Thermal conductivity suitable for maintaining body temperature