In which situation would it be crucial to use supplemental oxygen for a diver?

Using supplemental oxygen becomes crucial in the event of symptoms of oxygen toxicity, which can occur when a diver is exposed to high partial pressures of oxygen, typically during deeper dives or prolonged exposure to enriched oxygen mixes. Oxygen toxicity can lead to serious health issues, including seizures and other neurotoxic effects.

In cases of suspected oxygen poisoning, administering supplemental oxygen can help alleviate the symptoms by flushing the system and reducing the partial pressure of oxygen around the diver, thus mitigating the risk of further complications. This intervention is essential for ensuring the diver's safety and facilitating recovery.

While diving deeper than 30 meters and prolonged dives without support can pose risks, these situations do not inherently require supplemental oxygen, unlike a situation involving symptoms of oxygen toxicity, which demands immediate action to prevent severe outcomes. Therefore, it's critical to focus on the management of oxygen toxicity to ensure diver safety effectively.