What percentage indicates an oxygen deficient atmosphere?

An oxygen deficient atmosphere is defined by a concentration of oxygen that falls below the normal atmospheric level, which is approximately 20.9%. When the oxygen level drops to 19.5%, it indicates a significant reduction, leading to an atmosphere considered oxygen deficient. This threshold is critical for safety, as it is the percentage at which individuals may begin to experience symptoms of oxygen deficiency.

In environments where the oxygen level is lower than this threshold, especially in confined spaces, there may be a risk of hypoxia, which can impair physical and cognitive functions. It is essential for water operators and others working in such environments to recognize this standard to ensure safety protocols are followed and appropriate measures are taken to safeguard health.