What unit of measurement is commonly used to express the accuracy of oxygen analysis?

The accuracy of oxygen analysis in diving is most commonly expressed as a percentage. This is because the primary concern when using nitrox is the percentage of oxygen in the gas mix, which directly affects both the dive's planning and safety protocols. For example, a nitrox blend may be labeled as EANx32, which indicates that the mix contains 32% oxygen and 68% nitrogen. This percentage is crucial for calculating oxygen exposure and planning dives to avoid nitrogen narcosis and oxygen toxicity.

The other options, while important in different contexts, do not directly apply to the measurement of oxygen in a dive setting. Parts per million is typically used for very trace amounts of substances and is not practical for standard nitrox diving applications. Pascals is a unit of pressure, which might be relevant in other aspects of diving but does not relate to oxygen concentration. Barometric pressure refers to the atmospheric pressure and can affect dive conditions but is not a measurement used to express oxygen analysis specifically. Therefore, percentage is the most appropriate and relevant unit for this context.