According to NFPA and OSHA, what does an atmosphere containing less than 19.5 percent oxygen indicate?

An atmosphere containing less than 19.5 percent oxygen is classified as oxygen-deficient. This threshold is significant because normal atmospheric air contains approximately 21 percent oxygen. Levels below 19.5 percent can pose serious health risks, including impaired judgment, reduced physical coordination, and in extreme cases, loss of consciousness or even death.

The Occupational Safety and Health Administration (OSHA) and the National Fire Protection Association (NFPA) utilize this standard to emphasize safety in environments where oxygen levels may drop due to various factors, such as confined spaces or enclosed areas with poor ventilation. When oxygen levels fall below this critical level, safety protocols must be followed, including using appropriate personal protective equipment (PPE) and ensuring proper ventilation before entry. This underscores the importance of monitoring oxygen levels to prevent dangerous situations for personnel.