This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Both metal and copper oxidize when exposed to oxygen and this is a natural process. Copper that is exposed to the outside environment is more likely to turn green and that is why copper vases and decorative pieces in gardens are often green.
Copper turns green because of an oxidation reaction; that is, it loses electrons when exposed to water and air. The resulting copper oxide is a dull green. This oxidation reaction is the reason the copper-plated Statue of Liberty is green rather than orange-red. According to the Copper Development Association, a weathered layer of copper oxide only 0.005 inches (0.127 millimeters) thick coats Lady Liberty.