In an oxygen-enriched atmosphere, what is the percentage of oxygen present?

In an oxygen-enriched atmosphere, the percentage of oxygen typically exceeds the normal atmospheric level of approximately 21% by volume. The standard atmospheric composition is about 78% nitrogen and 21% oxygen, with trace amounts of other gases.

An oxygen-enriched atmosphere is defined when the oxygen concentration is significantly higher than the normal level, which can enhance combustion and create a hazardous environment. The choice that indicates a higher concentration of oxygen than normal atmospheric levels is 23.5%. This percentage signifies an environment where oxygen levels are elevated enough to potentially support fire behavior beyond typical conditions, increasing the risk of fire incidents.

Therefore, this choice reflects the standard definition of an oxygen-enriched atmosphere, which is important for understanding fire behavior and safety protocols in firefighting.