Irc 2003 G2414.5.2
... copper and brass tubing shall not be used if the gas contains more than an average of 0.3 grains of hydrogen sulfide per 100 standard cubic feet of gas.

Local gas supplier should be able to tell you the H Sulfide content.

It is understood that Natural Gas can't use copper but Propane can around my area.

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Jim Luttrall
Mr. Inspector.net, Inc.
Allen, Texas 75002