According to safety standards, what must cylinders be equipped with?

Cylinders must be equipped with an overfilling prevention device that meets specific standards to ensure safety during the refueling process. This device is critical because it helps to prevent the accidental overfilling of the cylinder, which can be dangerous and lead to leaks or other hazardous situations. Such devices ensure that gas does not escape into the atmosphere and helps maintain the safety of both users and the environment.

While emergency pressure relief devices and impact-resistant outer casings contribute to safety, they do not directly address the specific requirement for preventing overfilling. A decorative protective covering, though it may have aesthetic value, does not serve any functional safety purpose in regard to the management of gas within the cylinder. Thus, having an overfilling prevention device aligns with regulatory safety standards and is essential for proper gas cylinder operation.