Diving physiology: Which inert gas replaces nitrogen in the breathing mix for deep-sea divers? Focus on avoiding nitrogen narcosis and improving gas properties at depth. Choose the correct gas.

Given data

• Context: Deep diving breathing mixtures.

Concept/Approach
To prevent nitrogen narcosis and reduce gas density at depth, divers use heliox (He + O₂) or trimix (He + N₂ + O₂). Helium replaces nitrogen as the primary inert diluent.

Reasoning
• Helium is inert, far less narcotic than nitrogen, and has lower density → easier breathing under pressure.

Final Answer
Helium