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

The correct answer is based on the regulatory requirements set by the Department of Transportation (DOT) for the servicing and lifespan of DOT 3HT oxygen cylinders. Under these regulations, a DOT 3HT cylinder must be retired after a maximum service life of 24 years or after 4,380 filling cycles, whichever comes first.

This retirement schedule is designed to ensure safety and reliability, as repeated fill cycles can lead to material fatigue and potential failure of the cylinder. For proper maintenance, periodic inspections and tests are also mandated during the operational period, ensuring that the cylinders remain in safe working condition until they reach either of those limits.