What does a + sign indicate on the back side of a cylinder marking?

• A. The tank can be filled to 100%
• B. The tank may be refilled 10% greater than service pressure
• C. The tank is awaiting inspection
• D. That the tank is newly manufactured

Answer: (B)

A + sign on the back side of a cylinder marking signifies that the cylinder may be refilled to a pressure that is 10% greater than its service pressure. This marking is an indication that the cylinder has been tested and is certified by the Department of Transportation (DOT) for increased pressure beyond the standard filling pressure. This is important for the operation of gas cylinders because it allows for a safe margin of pressure that can accommodate gas expansion and variations in atmospheric conditions without compromising safety.

Understanding this marking is crucial for users who handle medical gas cylinders, as it informs them of the ability to fill the tank to a higher capacity safely. It reflects compliance with regulatory standards that prioritize safety and operational efficiency in gas storage and transport.