Thanks, the reason I wondered about that is because there are some CGA580 valves with a burst disc, where AFAIK CGA580 is only for noble gases and mixtures of noble gases with CO2.
granted thats for us UK folk , maybe your local regulations may be different , but burst discs are on fuel gas cylinders only , and even then its only on lower pressure cylinders ,,
I guess as you mentioned this has something to do with variying regulations.