What is considered oxygen deficiency?

Oxygen deficiency is defined as air that has less than 19.5% oxygen or greater than 23.5% oxygen. This is significant because levels below 19.5% indicate a hazardous condition where a person may not receive enough oxygen for normal bodily functions, leading to physiological effects such as dizziness, unconsciousness, or even death. Conversely, air that exceeds 23.5% oxygen can pose a different kind of risk, as it can create an explosive atmosphere, making any spark or flame dangerously reactive.

Understanding these parameters is crucial in environments where respiratory hazards may be present, such as in asbestos investigation, as maintaining adequate oxygen levels is essential for the safety of personnel working in potentially dangerous conditions. The other choices do not accurately define the parameters of oxygen deficiency: oxygen levels over 21% indicate safety but do not constitute deficiency, while air that is free of contaminants does not directly relate to oxygen levels.