Oxygen deficiency is defined as oxygen levels below what percentage?

Oxygen deficiency is typically defined as a condition where oxygen levels fall below 19.5% in the atmosphere. This threshold is critical because oxygen levels at or above 19.5% are considered safe for human health, while levels below this can lead to various health risks, including impaired cognitive function, dizziness, and even unconsciousness.

The reason this specific percentage is used relates to the body's requirement for oxygen to function effectively. Sustained exposure to oxygen levels below 19.5% can be detrimental, especially in enclosed or confined environments, such as mines, where oxygen levels may fluctuate due to various factors like gas emissions or dispersal.

Values above this threshold, such as 20% or 21%, are still within the normal range for breathable air, and levels below 18% signal a more severe oxygen deficiency. Therefore, recognizing 19.5% as the critical cutoff for oxygen deficiency is essential for safety protocols in environments where oxygen levels can be compromised.