DOT cylinders shall NOT be refilled, continued in service or transported unless they are properly __________.

DOT cylinders must be properly re-qualified to ensure they meet safety and performance standards set by the Department of Transportation. Re-qualification is crucial because it involves thorough inspection and testing of the cylinder to verify its ability to safely contain propane under pressure. This process helps identify any weaknesses, such as corrosion or damage, that could lead to hazardous situations, including leaks or ruptures.

The re-qualification process typically occurs at specific intervals, depending on the cylinder's design and usage conditions. Only cylinders that have passed this re-qualification can be safely filled and transported. Hence, ensuring that a cylinder is properly re-qualified is an essential step in maintaining safety standards within the propane industry. While inspection, maintenance, and proper manufacturing are important components in the lifecycle of a cylinder, they do not specifically address the regulatory requirement for continued service and safe transport as re-qualification does.