What condition must DOT cylinders meet before they can be refilled or transported?

For a DOT cylinder to be refilled or transported, it must have undergone the proper re-qualification process. This ensures that the cylinder is safe for continued use and has been inspected for any signs of wear, damage, or corrosion that could lead to failure during use or transport. Re-qualification verifies that the cylinder meets the necessary safety standards and can safely hold propane or other gases without posing a risk to users or the environment.

While securing and painting cylinders are important aspects of overall safety and maintenance, they do not address the critical concern of the cylinder's structural integrity and compliance with safety standards. Furthermore, a cylinder being empty does not inherently mean it’s safe for refill or transport; it still requires re-qualification to ensure it can handle the pressures and conditions present during filling and in service.