What percentage of oxygen is required to consider a space safe?

The correct percentage range for oxygen concentration that is considered safe in a space is between 19.5% to 22%. This range is critical because oxygen levels below 19.5% can lead to an oxygen-deficient atmosphere, which poses hazards like impaired cognitive function, decreased physical capability, and even loss of consciousness. On the upper end, levels above 22% can increase the risk of fire and explosion, as higher concentrations of oxygen can make materials more combustible.

This range is established by safety standards and guidelines to ensure a safe working environment, particularly in industries where personnel may be exposed to variations in atmospheric conditions. Maintaining oxygen levels within this specific range is essential for worker safety and the prevention of accidents related to both oxygen deficiency and excess.

Options that fall outside of this range either do not account for the necessary safety buffer or include values that could potentially lead to dangerous situations, thus illustrating why the chosen percentage of 19.5% to 22% is both scientifically backed and prioritizes safety.