SSI Specialty Course Enriched Air Nitrox (SC-EAN) 40% Level 2 Practice Test 2026 - Free Enriched Air Nitrox Practice Questions and Study Guide

Nitrogen is the correct answer because it plays a crucial role in preventing oxygen toxicity during diving. At higher partial pressures, oxygen can become toxic, leading to serious health risks such as convulsions and loss of consciousness. Nitrogen, the most abundant gas in the air we breathe, is relatively inert and does not contribute to the toxicity associated with increased oxygen levels at depth.

When divers breathe air, they inhale a mixture that includes about 21% oxygen and 79% nitrogen. Because nitrogen does not have the same toxic effects at increased pressures as oxygen can, it helps to dilute the oxygen, ensuring that the partial pressure of oxygen remains within safe limits for divers. This balance is essential to avoid complications related to oxygen toxicity, especially during deep dives where partial pressures of gases become significantly elevated.

In contrast, carbon dioxide can lead to increased respiratory drive and discomfort if levels rise too high, potentially complicating dives but not directly preventing oxygen toxicity. Helium, while also being used to mitigate the risks of narcosis in deep diving, does not directly influence oxygen toxicity in the way nitrogen does. Argon, typically present in small amounts in air, has little relevance to the management of oxygen toxicity during diving.