At what oxygen level does a person typically lose consciousness?

A person typically loses consciousness at an oxygen level of 16%. This is considered a critical threshold where the body's ability to utilize oxygen becomes severely impaired. At this level, symptoms such as confusion, dizziness, and shortness of breath may occur preceding loss of consciousness if exposure continues. The oxygen concentration in normal atmospheric air is around 20.8%, and while lower levels can affect performance and awareness, significant impairment, including loss of consciousness, is expected to occur at around 16%.

In contrast, an oxygen level below 19.5% indicates the onset of hypoxia, where individuals may begin to experience symptoms but may not yet lose consciousness. Levels of 8-12% would be life-threatening scenarios where unconsciousness likely occurs much sooner.