Which gas is most commonly used as a reference during calibration?

The most common gas used as a reference during calibration is pure air. Calibration of gas analyzers and diving equipment typically requires stable and known reference points to ensure accuracy. Pure air, which is composed of approximately 21% oxygen and 79% nitrogen, serves as an effective baseline for many diving applications since it reflects the natural atmosphere and is readily accessible.

Using pure air allows divers and technicians to establish a reference for analyzing mixed gases like Nitrox, as it provides a clear comparison to the nitrogen and oxygen levels in the breathing mixtures that divers will use. This is critical for ensuring that the analyzers accurately measure the partial pressures of the gases involved in diving, thus promoting safety and optimal performance.