A cylinder with a(n) ____________, even if it appears to be undamaged, shall NOT be refilled until it is requalified by the methods prescribed in DOT regulations.

A cylinder with an expired requalification date cannot be refilled, even if it appears to be undamaged, because the date indicates that it has not undergone the necessary inspections and tests required by the Department of Transportation (DOT) regulations to ensure its safety and integrity. Requalification is essential for maintaining the structural integrity of the cylinder and confirming that it can safely contain propane under pressure without the risk of leaks or failure. The requalification process includes testing for mechanical integrity and any flaws that may not be externally visible.

While visible dents, scratches, and severe corrosion also pose safety concerns and could prevent a cylinder from being refilled, it is particularly important to adhere to the requalification dates because they encompass a broader range of assessments, ensuring that all aspects of the cylinder's safety have been evaluated. A newly painted surface does not imply the cylinder's structural integrity or safety and could potentially mask underlying issues, but it does not affect the necessity for requalification. Thus, the emphasis on an expired requalification date highlights the importance of regulated safety practices in propane cylinder handling.