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.
I've even seen claims that the blue of a gas flame is due to the copper tubing used in the burner. All I can say is, if your furnace is emitting vaporized copper into your living space, you'd better find a safer heating system like, say, setting your sofa on fire. To be fair, blue and green flames can be due to copper.