Recently, many scientists are trying to demonstrate that some geochemical tracers of magmatic processes (e.g., CO2/SO2 and SO2/HCl ratios) are stable when measured far from the emission vents, speculating on the possibility to carry out monitoring of volcanic activity in this way.

My thought is that some acidic species, such as for instance HCl, very hardly remain stable in atmosphere, even more if far from the craters.