After how many years or filling cycles must a DOT 3HT oxygen cylinder be retired from service?

The correct answer provides the retirement criteria for a DOT 3HT oxygen cylinder, which is governed by regulations set forth by the Department of Transportation. Specifically, a DOT 3HT cylinder must be retired after either 24 years from the date of its manufacturing or after it has undergone 4,380 filling cycles.

This retirement schedule accounts for both time and the number of fills because the structural integrity of the cylinder can degrade with usage and age. The 24-year mark ensures that any potential fatigue or degradation from normal wear and tear is addressed, while the limit on filling cycles acknowledges the cumulative stress placed on the cylinder from repeated pressurization and depressurization.

In contrast, other options do not align with the established guidelines for the DOT 3HT cylinders, which are clearly defined in the relevant regulations regarding the safe handling and operational life of such equipment. Compliance with these standards is essential for ensuring the safety and reliability of oxygen delivery systems.