IANTD Enriched Air (Nitrox) Practice Test

Dalton's Law states that in a mixture of gases, the total pressure exerted is equal to the sum of the partial pressures of each gas in the mixture. In the context of gas mixtures like air, understanding how to calculate the partial pressures is vital, especially when dealing with different gas compositions, such as enriched air (Nitrox).

The formula to calculate the partial pressure of a specific gas, such as oxygen, involves the total pressure of the gas mixture and the fraction of the gas present in the mixture. For oxygen, the partial pressure (PO2) can be calculated by multiplying the total atmospheric pressure (PATM) by the fraction of oxygen in the mixture (FO2). It is important to note that this calculation applies when considering the mixture of gases we breathe, which includes oxygen and nitrogen, among others.

The correct way to express this calculation is through the relationship: PO2 = PATM x FO2. This formula directly applies Dalton's Law by asserting that the partial pressure of oxygen in a gas mixture is a product of the total pressure and the proportion of oxygen within that mixture. Therefore, recognizing that PATM refers specifically to atmospheric pressure, not just any pressure source, is pivotal when applying this principle.

Using total atmospheric