What is the primary hazard of breathing 100% oxygen at depth?

Breathing 100% oxygen at depth poses significant risks, with oxygen toxicity being the primary hazard. At increased pressures, such as those experienced while diving, the partial pressure of oxygen rises, which can lead to harmful physiological effects. Oxygen toxicity can manifest in two main forms: central nervous system (CNS) toxicity and pulmonary toxicity. CNS toxicity may result in symptoms like visual disturbances, muscle twitching, seizures, and can potentially lead to loss of consciousness, while pulmonary toxicity occurs with prolonged exposure to high partial pressures of oxygen and can lead to inflammation of lung tissue.

This is particularly relevant in diving situations where shallow or longer-duration exposure to high concentrations of oxygen can significantly increase the chances of experiencing these toxic effects. Understanding the implications of oxygen partial pressure is crucial for divers, as managing oxygen exposure is integral to their safety and well-being underwater.

In contrast, the other options, while they may pose serious risks in certain contexts, do not directly relate to the immediate dangers associated with breathing pure oxygen under pressure. Decompression sickness occurs from the formation of nitrogen bubbles during ascent, carbon dioxide poisoning arises from insufficient ventilation, and hypoxia is a condition of low oxygen availability, which is less likely when breathing pure oxygen.