Which of the following is a safety requirement for LP-gas cylinders not filled on site?

The requirement for LP-gas cylinders not filled on site to have warning labels is crucial for safety and hazard identification. Warning labels serve as visual alerts, informing users about the contents of the cylinder and the associated risks. This is essential for ensuring the proper handling and storage of the cylinders, as well as for informing emergency responders in case of an accident or leak.

Clear labeling helps prevent misuse, such as using the wrong equipment for a specific type of gas. The information on the warning labels typically includes the type of gas, safety precautions, and emergency contact information, thereby promoting a safer environment for everyone involved.

The other options, while related to safety, do not specifically address the fundamental necessity of labeling. For example, tagging annually might refer to maintenance checks but does not directly inform users of the hazards. Similarly, while storage conditions are important for safety, they don't substitute for the clear communication provided by warning labels. Lastly, closing mechanisms are essential for safety, but they pertain more to preventing leaks than to the identification of hazards associated with the contents of the cylinders.