At what oxygen level does a person typically lose consciousness during a fire?

A person typically loses consciousness at an oxygen level of around 10%. In environments with reduced oxygen levels, such as during a fire, the body struggles to acquire the necessary oxygen for brain function. Normal atmospheric oxygen levels are approximately 21%. Below this level, the body's ability to function properly diminishes significantly.

When oxygen levels drop to about 10%, the risk of unconsciousness becomes critical, as the brain requires a sufficient supply of oxygen to maintain consciousness and perform essential functions. At levels around or below this threshold, individuals can experience confusion, disorientation, and ultimately loss of consciousness as the body is deprived of the oxygen it needs.

Levels below 10% can be life-threatening, and different people may experience varying degrees of effects at adjusted oxygen levels, but loss of consciousness is a distinct point that correlates with about 10% oxygen concentration.