What item must be present on all portable refillable cylinders to ensure consumer safety?

The presence of warning labels on portable refillable cylinders is vital for consumer safety as they provide essential information regarding the hazards associated with the product. These labels inform users about the contents of the cylinder, potential risks, and necessary precautions for safe handling and use. Warning labels may also include instructions for safe operation and emergency information, which are crucial in preventing accidents and ensuring that users are aware of potential safety issues when using LP-gas.

In the context of handling LP-gas, it is important for consumers to be well-informed about the risks, and warning labels serve as a critical educational tool. Labels help in identifying the type of gas as well, which is significant in avoiding improper use or mix-up with other gases that may have different properties and safety concerns. Hence, their presence contributes to a safer environment when handling and utilizing portable refillable cylinders.