Scuba Diving International (SDI) Computer Nitrox Practice Exam

What is the minimum concentration of oxygen required to maintain consciousness at sea level?

1. 15%

2. 16%

3. 18%

4. 20%

The correct answer is: 16%

The minimum concentration of oxygen required to maintain consciousness at sea level is 16%. This percentage reflects the threshold for safe oxygen levels in the atmosphere, enabling normal physiological function without the risk of hypoxia (insufficient oxygen to the body). At concentrations lower than this level, individuals may begin to experience symptoms of hypoxia, such as impaired cognitive function, decreased physical coordination, and ultimately, loss of consciousness. Being at sea level, the typical atmosphere contains about 21% oxygen; therefore, 16% is notably below standard atmospheric oxygen levels, yet it is still the minimum required to support consciousness. If the oxygen concentration drops to 15% or lower, individuals may risk experiencing adequate signs of hypoxia. Understanding these percentages is essential for divers, particularly in contexts where oxygen levels can vary, such as in diving environments with enriched air nitrox or during emergencies involving oxygen depletion. This knowledge allows divers to make informed decisions to maintain safety and avoid potentially life-threatening situations underwater.