Which inspection method requires visually checking the condition of a DOT cylinder?

The correct answer is the External Visual Inspection Method because it specifically involves a thorough visual check of the outside condition of a Department of Transportation (DOT) cylinder. During this inspection, the technician looks for signs of wear, corrosion, dents, or any significant defects that could compromise the cylinder's integrity and safety.

This method is critical for ensuring that the cylinders are safe for use and meet regulatory standards. It is the first line of defense in identifying potential issues without the need for specialized equipment or procedures. By focusing on the exterior, inspectors can quickly assess whether a cylinder may pose a risk before further testing or use.

Other methods such as the Proof Pressure Method and the Volumetric Expansion Method involve more complex procedures that usually assess the cylinder’s performance or structural integrity under pressure rather than a straightforward visual check. Safety Protocol Inspection generally encompasses a broader review of multiple safety measures and procedures rather than focusing specifically on the visual state of the cylinder itself.