We need to concern ourselves with all pieces of our equipment which comes in contact with:

The correct choice is Nitrox, which is a specific blend of oxygen and nitrogen used in diving. When using enriched air nitrox, it is essential to consider all equipment that comes into contact with this gas mixture because of the increased oxygen content compared to regular air. The presence of a higher proportion of oxygen can affect various materials, leading to issues such as oxygen toxicity and degradation of certain substances, which may not occur with air or nitrogen alone.

Materials that are safe for regular air use may not be appropriate for nitrox due to the risk of fire or equipment failure. Factors such as the type of lubricant, the condition of tank valves, and the compatibility of hoses and regulators must be reviewed to ensure safety and functionality.

The other options—air, nitrogen, and water—do not carry the same level of concern regarding equipment compatibility when compared to nitrox, due to the specific challenges associated with high oxygen environments that enriched air presents.