What percentage of oxygen in the atmosphere is considered 100% fatal within 8 minutes?

The correct answer is that 4-6% oxygen in the atmosphere is considered 100% fatal within 8 minutes. In environments with such low oxygen levels, the human body cannot sustain normal physiological functions, leading to loss of consciousness and death within a short period. Oxygen levels around this range create a critical lack of breathable air, which can quickly result in asphyxiation.

In contrast, higher oxygen levels do not have the same immediate life-threatening risks associated as they are still within the range the body can tolerate, even though they can still pose risks over time. Thus, 4-6% signifies a dire situation where survival is virtually impossible due to inadequate oxygen supply.