What is the minimum permissible oxygen level by volume to avoid negative effects?

The minimum permissible oxygen level by volume to avoid negative effects is 19.05%. This percentage is important because normal atmospheric oxygen content is approximately 21%. As oxygen levels decrease, various physiological effects and health risks may arise. Relying on levels under 19.05% can lead to symptoms of hypoxia, which include reduced cognitive function, impaired motor coordination, and other significant health issues. Thus, maintaining oxygen levels at or above this threshold is crucial for ensuring adequate oxygenation for individuals, especially in settings where oxygen is consumed in higher amounts or where ventilation may be limited.