What is defined as an Immediately Dangerous to Life or Health (IDLH) percentage of oxygen?

An Immediately Dangerous to Life or Health (IDLH) percentage of oxygen is defined as a level of oxygen that poses a direct threat to health or life, typically indicating an oxygen deficiency that could lead to unconsciousness or death. The standard threshold for a safe oxygen level in the atmosphere is generally accepted to be around 19.5% oxygen. Below this percentage, individuals may experience symptoms of hypoxia, which can impair physical and mental performance, potentially leading to incapacitation or fatal consequences.

In health and safety regulations, anything above this level is considered safe for breathing, while values below 19.5% fall into the IDLH category due to increasing risks associated with lower oxygen levels. Therefore, recognizing 19.5% as the threshold for IDLH situations is vital for the safety of individuals working in potentially hazardous environments, such as firefighting or rescue operations.