To avoid the medical condition called 'bends' in scuba divers, the composition of gas filled in the tank is

Helium 11.7%, Nitrogen 56.2%, Oxygen 32.1%

The correct answer is Option (1) → Helium 11.7%, Nitrogen 56.2%, Oxygen 32.1%

When scuba divers descend to great depths, the high pressure causes atmospheric gases (primarily Nitrogen) to dissolve more readily into their blood and tissues (according to Henry's Law). If the diver ascends too quickly, the pressure decreases rapidly, and the dissolved nitrogen comes out of solution, forming bubbles in the bloodstream. This painful and potentially fatal condition is known as Decompression Sickness or "the bends."

To mitigate this risk, air in scuba tanks is diluted with Helium. Helium is used because:

• It has very low solubility in human blood compared to Nitrogen.
• Its atoms are small and diffuse out of tissues more quickly and safely.
• It helps prevent nitrogen narcosis, a feeling of intoxication caused by breathing nitrogen at high pressures.

The Standard Composition The specific mixture used to prevent these conditions typically consists of:

• Helium: 11.7%
• Nitrogen: 56.2%
• Oxygen: 32.1%