The maximum spacing for labeling copper tubing systems is:

The correct answer reflects the standard practice for labeling copper tubing systems, which stipulates that labels must be affixed at designated intervals. The maximum spacing of 6 feet serves to ensure that anyone working on or around the piping can easily identify its contents and purpose, contributing to safety and efficient maintenance. Proper labeling is crucial in avoiding errors in service and repairs, especially in environments where multiple types of systems may be present. This regular spacing helps maintain clarity and visibility for workers, ensuring that all safety protocols are followed. Having a labeling standard also aids in compliance with local codes and industry regulations, which often emphasize the importance of clear identification of pipes for hazard communication.