A. Brass and copper pipe or tubing must not be used where the gas contains more than an average of 0.3 grams of hydrogen sulfide per 100 scf (standard cubic feet) of gas (0.7 mg/100) according to section 1208.5.2.3 of the 2012 Uniform Plumbing Code and section 54.5.6.2.3 of the NFPA (National Fire Protection Association) fuel gas code. Since natural gas can contain some hydrogen sulfide, these brass flare fittings are not recommended. Galvanized and black steel pipe and fittings can be used if it is standard weight Schedule 40 or thicker.