Why is having an additional gas supply recommended during deep dives?

Having an additional gas supply during deep dives is recommended primarily because the breathing gas supply becomes the limiting factor. At greater depths, the consumption of breathing gas increases due to the higher pressure and the physiological demands on the diver's body. In environments where depths and durations extend beyond typical recreational limits, the risk of running low on breathable gas can become significant. Inadequate gas can lead to critical situations, including the inability to complete a safe ascent or perform necessary safety stops, which are crucial for preventing decompression sickness.

Having an additional gas supply serves as a safety measure that ensures divers have sufficient gas to manage unexpected circumstances such as emergency situations, extended decompression stops, or equipment failures. This extra supply provides peace of mind and is a key aspect of dive planning and safety protocols, enabling divers to respond effectively to challenges encountered during deeper dives.