Which gas is primarily associated with the risk of decompression sickness?

The gas primarily associated with the risk of decompression sickness is nitrogen. When divers ascend from depths where they are breathing compressed air or nitrox mixtures, nitrogen, which is a major component of these gases, becomes less soluble in the bloodstream due to the decrease in pressure. If a diver ascends too quickly, nitrogen bubbles can form in the tissues and bloodstream, leading to decompression sickness, often referred to as "the bends." This condition can cause severe pain and injury, making understanding nitrogen's role in diving physiology critical for divers.

While oxygen, hydrogen, and helium each have unique properties and concerns in diving, they are not primarily associated with decompression sickness. Helium is sometimes used in deep diving situations to help reduce the risk of nitrogen narcosis and has a lower tendency to form bubbles. Oxygen toxicity is a concern at high partial pressures but does not relate to decompression sickness in the same way that nitrogen does. Therefore, recognizing nitrogen as the primary gas linked to this risk is essential for safe diving practices.