I got an interesting question after asking a local CO2 supplier whether they carried CGA320 adapters (nipple & nut) since I needed to replace the existing CGA350. He was concerned and asked me what gas the regulator was used for since a 350 is mostly used for methane, hydrogen and other explosive gases. His concern was whether the regulator (an E12 244b) could or should be used with CO2. I did tell him that it was a new reg. and never used.
He may not know much about regulators specifically which prompted the question.
I assume there really is no concern with converting from its intended gas to CO2 ??