What is a requirement for a DOT Composite Cylinder propane container before recertification is required?

For a DOT Composite Cylinder propane container, recertification is required after a specific period of use to ensure safety and compliance with regulations. The correct requirement is that a composite cylinder must undergo recertification after 5 years of use. This is crucial because over time, exposure to various environmental factors can affect the integrity and safety of the cylinder, potentially leading to hazardous situations if not properly maintained or replaced. Regular recertification helps identify any structural weaknesses or defects that may have developed, ensuring the safe storage and transport of propane. This practice aligns with safety standards and helps to protect users and the environment.