An oxygen deficient atmosphere is considered to be below what percentage?

An oxygen deficient atmosphere is recognized when the concentration of oxygen falls below 19.5% by volume. In normal atmospheric conditions, the oxygen content is about 21%. At levels below 19.5%, individuals may begin to experience symptoms of hypoxia, which can impair physical and cognitive functions. This threshold is critical in various safety and health regulations, particularly in environments where work may involve hazardous materials or confined spaces. Understanding this standard is essential for volunteer firefighters, as they often operate in conditions where oxygen levels may be compromised, ensuring that they can take appropriate precautions to safeguard their health and safety.