What should be done with valves on empty gas cylinders?

When dealing with empty gas cylinders, the valves should be closed to prevent gas leaks. It's essential to ensure that the cylinders are completely sealed when not in use to mitigate any risk of gas escaping, which could create a hazardous environment. Closing the valves also prevents contaminants from entering the cylinder, which could pose safety concerns if the cylinder is reused or refilled in the future.

The practice of closing valves is part of standard safety protocols in handling gas cylinders. This precaution is crucial in both storage and transportation to ensure the safety of personnel and the integrity of the gases contained within. Keeping the valves closed minimizes the chance of accidental releases and ensures that the empty cylinder is handled in a way that maintains safety standards.

In contrast, other choices may lead to hazardous situations. Leaving the valves open is unsafe, as it may allow residual gas to escape, which can cause flammable or toxic environments. Removing valves could compromise the structure of the cylinder and isn't a standard procedure for safety, while painting the cylinder to indicate emptiness does not address the fundamental issue of sealing the potential for leaks. Safety protocols prioritize the integrity of gas storage systems, making valve closure the correct and responsible action.