How is the percentage of oxygen typically adjusted in blended gas mixtures?

The percentage of oxygen in blended gas mixtures is adjusted primarily by adding pure oxygen to a nitrogen-dominated mix. This method allows for precise control over the oxygen content in the gas mixture. When pure oxygen is introduced into the mix, it directly increases the concentration of oxygen relative to the inert gases, such as nitrogen, resulting in a higher percentage of oxygen in the final blend.

This process is crucial for creating specialty gases that cater to various diving needs, especially for enriched air nitrox, where specific oxygen percentages are required for safe diving. The ability to adjust the oxygen percentage by this method is fundamental to the formulation of gas mixtures that provide the desired benefits while avoiding risks associated with elevated oxygen levels at depth.