What defines the "best gas mix" for a dive?

The definition of the "best gas mix" for a dive is centered around the optimal blend of oxygen and nitrogen tailored for the specific depth you will be diving. This consideration is crucial because different depths exert varying pressures on divers, which affect the solubility of gases in body tissues and the risk of decompression sickness. A carefully calculated mix ensures that oxygen levels are sufficient for safe breathing while preventing nitrogen narcosis and minimizing the risk of nitrogen becoming overly saturated in body tissues at greater depths.

Furthermore, the ideal gas mix remains within the physiological limits for the diver. By optimizing the ratio of oxygen to nitrogen, divers can maintain safety and comfort during their dive and when ascending back to the surface. Consequently, the chosen mix must take into account not just the depth but also the planned duration of the dive and the profile of the ascent. This helps in reducing the likelihood of decompression incidents significantly.

Other choices, such as random blends or equal mixtures of gases, do not adhere to these physiological principles and thus would not produce a safe or effective mix for diving purposes.