What factor primarily leads to running out of breathing gas?

The primary factor that leads to running out of breathing gas is failing to monitor the pressure gauge or air-integrated dive computer. By neglecting to keep an eye on how much gas remains, a diver may inadvertently consume all available breathing gas without realizing it. This can lead to a critical situation where the diver is left without sufficient gas to return to the surface safely.

Monitoring the pressure gauge is essential during a dive to ensure there is enough gas for both ascent and any necessary safety stops. An air-integrated dive computer can provide real-time data on gas consumption and remaining gas supply, making it even easier for divers to manage their gas supply effectively. By actively checking these instruments, divers can make informed decisions about their dive time and depth, ultimately enhancing safety and preventing gas depletion during the dive.

The other factors, while they may contribute to dive safety concerns, do not directly correlate with the most significant cause of gas running out as effectively as failing to monitor the pressure gauge or dive computer.