When is it permissible to refill a DOT cylinder?

Refilling a DOT (Department of Transportation) cylinder is permissible when it has been re-qualified, which means that it has undergone a thorough inspection and certification process to ensure it meets safety standards. Over time, propane cylinders can experience wear and tear, and re-qualification confirms that a cylinder is still safe to be filled and used. This process typically involves checking for structural integrity and ensuring that the cylinder adheres to current regulations and standards.

While being in good condition is essential for any propane cylinder to be filled, re-qualification is a specific requirement to ensure the cylinder's continued safety and compliance with regulations. Other considerations, such as being properly marked, are important for identifying the cylinder's suitability for use, but re-qualification specifically addresses the safety of refilling the cylinder. Lastly, the amount of propane already in the cylinder does not determine its eligibility for refilling; it can be filled regardless of the remaining gas, as long as it has been re-qualified and meets all other safety criteria.