What is the FiO2 of room air?

The fractional inspired oxygen (FiO2) of room air is approximately 21% or 0.21. This means that in the normal atmosphere, the concentration of oxygen present in the air we breathe is roughly one-fifth of the total gas composition.

In typical atmospheric conditions, air is made up of about 78% nitrogen and 21% oxygen, with trace amounts of other gases. This composition is consistent at sea level for healthy adults in environments without significant air pollution or other influences.

Understanding the FiO2 is crucial in clinical settings, as it provides a baseline for assessing a patient's oxygenation and can guide interventions such as supplemental oxygen therapy, which may increase the FiO2 to higher levels when necessary. Other options suggest significantly lower or higher percentages that do not reflect the actual composition of room air and would not be accurate in a typical context.