Copper with a green stamp is used in a Med Gas system. What grade of copper does the color denote?

Many states require building contractors to be licensed. To get licensed, you may need to take a business and law exam, as well as a trade exam. The business and law portion will cover such subjects as contracts, estimates, bidding, bonding, accounting, business forms, environmental regulations, safey and quality control. The trade portion of the exam will cover subjects such as plan reading and estimating, site engineering, sitework and excavation, footings and foundations, concrete, masonry, carpentry, metals and safety.