Laboratory experiments indicate that gas permeability is two to five times higher than water permeability in basalts and andesites. These results have important implications for fluid flow and therefore the distribution and build-up of pore pressure within volcanic systems.
Source: M.J. Heap et al., 2018. Permeability of volcanic rocks to gas and water”. Journal of Volcanology and Geothermal Research, 54(1), pp. 29-38. https://doi.org/10.1016/j.jvolgeores.2018.02.002