John,
I suppose I was being a little facetious. I am aware of the idea of Metal Active Gas. And you're right, the terminology is used more often in europe especially, but perhaps elsewhere as well. We don't use it much here (the AWS from on high choosing the GMAW abbreviation and MIG being non standard-perhaps we need AGMAW
). The IIW, based in Paris (though there is an office in Florida), has hundreds of articles on the subject. I have a few in this pile of shyt I call a library. But I am not aware of any special hardware associated with it. My understanding is that its simply a gas relationship in which case chemically active gases such as oxygen and CO2 would be applicable.
Anything other than inerts (Ar, He, etc.) utilized as a gas shielding would be considered active, carbon and oxygen being the biggies but N as well. There may be some more specificity to it but my memory fails me in my grizzled years.