SSI Science Of Diving Practice Exam

To maintain consciousness at sea level, a gas mixture must contain at least 16% oxygen. This percentage is critical because it is the minimum concentration of oxygen in the air that supports human life and prevents unconsciousness due to hypoxia. At sea level, the atmosphere is composed of approximately 21% oxygen, which is more than sufficient for sustaining consciousness. When the oxygen concentration drops below about 16%, the risk of losing consciousness increases significantly. As ambient pressure changes, such as during descent in diving, maintaining an appropriate oxygen level becomes essential for the diver's safety and operational effectiveness. A mixture with only 10%, 5%, or any percentage lower than the critical threshold would not provide enough oxygen for the sustaining metabolic functions necessary for consciousness, leading to potential dangers including disorientation or loss of consciousness. This context highlights the importance of understanding oxygen levels in gas mixtures and their impact on diver safety and physiology.