What is the gas mixture used for depths between 166 to 225 FSW?

The gas mixture of 64% helium and 36% oxygen is specifically formulated for depths between 166 to 225 feet of seawater (FSW) to provide safe and effective breathing conditions for divers at these deeper depths.

At such depths, using pure oxygen or air can lead to serious physiological problems, such as oxygen toxicity or nitrogen narcosis. The inclusion of helium in the mixture serves to lower the risk of these conditions, since helium is an inert gas that helps reduce the effects of narcosis and allows for safer breathing under increased pressure. The particular ratio of 64% helium and 36% oxygen has been determined through extensive research and practice in deep-sea diving to optimize the balance between the risks associated with oxygen toxicity and narcosis while ensuring adequate oxygen supply for metabolic needs.

In summary, this specific gas mixture is tailored for the increased pressures and risks faced in deeper dives, making it crucial for divers to use this blend to ensure their safety and health underwater.