What is the threshold for low oxygen levels?

Low oxygen levels are defined concerning the normal atmospheric concentration of oxygen, which is approximately 20.9%. A threshold below 19.5% is typically recognized as an oxygen-deficient atmosphere, which can pose health risks and become hazardous for individuals who are working in such conditions. The correct choice establishes 19.5% as the lower limit for acceptable oxygen levels. It indicates that at or below this percentage, there could be significant impairment of cognitive and physical abilities due to insufficient oxygen for breathing, leading to symptoms such as dizziness, shortness of breath, and in extreme cases, loss of consciousness. Therefore, 19.5% is the benchmark utilized in safety protocols to ensure the environment remains safe for personnel operating in hazardous conditions.