Below what percentage of oxygen is considered "oxygen deficient"?

An environment is considered "oxygen deficient" when the oxygen concentration in the air falls below 19.5%. This threshold is crucial for safety practices, particularly in confined spaces or during activities that may lead to exposure to hazardous materials, such as asbestos work. The standard for oxygen deficiency is set to ensure that workers are not exposed to a situation where there is an insufficient supply of oxygen, which can lead to serious health risks, including loss of consciousness or even fatalities.

The choice of 19.5% is also aligned with occupational safety regulations, which stipulate that 21% oxygen is the norm in a typical atmosphere. Recognizing the point at which oxygen levels drop beneath 19.5% enables workers and safety personnel to take appropriate action, such as ventilating the area, using respiratory protection, or potentially evacuating the space.