If there is uncertainty about the O2 rating of a cylinder, what is the appropriate action?

When there is uncertainty about the O2 rating of a cylinder, it is essential to treat it with caution to ensure safety. Handling the cylinder as oxygen rated is crucial because enriched air nitrox has a higher concentration of oxygen than air, which can lead to potential hazards if contaminants are present. If the cylinder's O2 rating is uncertain, conducting an O2 cleaning before its next filling is the most responsible course of action. This cleaning process ensures that any hydrocarbons or contaminants that could pose a fire or explosion hazard are removed, thereby making the cylinder safe for oxygen service.

By thoroughly cleaning the cylinder, you mitigate the risk of dangerous reactions that could arise when a high concentration of oxygen comes into contact with unsuitable materials. This preventative measure underscores the importance of maintaining safety standards in scuba diving practices, especially when dealing with enriched air nitrox. Ensuring that equipment is compatible and well-prepared for specific gas mixes is critical for divers' safety.