What's a reasonable flow rate/mass flux for a fumarole?
Surprisingly enough most of the figures I could find were actually about thermal output but back working the figures, and assuming I read the formulas properly (not guaranteed I'm afraid) it looks like 5-7 litres per second is the ballpark average gas flow based on fifty years worth of data from several fumarole fields in the central North Island of New Zealand. I have no idea how representative that figure would be of fields elsewhere.