What is the minimum oxygen level required for safe breathing?

The minimum oxygen level required for safe breathing in most environments is commonly cited as 19.5%. This percentage is the threshold where healthy individuals can breathe normally without experiencing any harmful effects. Levels below this can lead to symptoms of oxygen deficiency, including dizziness, shortness of breath, and impaired cognitive function. The Occupational Safety and Health Administration (OSHA) defines 19.5% as the lower limit for oxygen levels in the air, below which workers must take precautions.

The higher percentages provided in the other options indicate that while they may provide even safer conditions for breathing, they do not represent the recognized minimum threshold. Therefore, while options higher than 19.5% are certainly better for oxygenation, they are not necessary for it to be considered safe.