A sampling tube for simultaneously and selectively sampling organic and metallic mercury vapors from air which comprises (a) a cylinder having an air intake end and an air outlet end, (b) a first particulate adsorber within said cylinder and adjacent said air intake end for selectively and quantitatively adsorbing organic mercurial vapors in air passing therethrough, (c) a second particulate adsorber within said cylinder for adsorbing metallic mercury in air passing therethrough, and (d) porous plug means for maintaining said first and second adsorbers in spaced relationship in said cylinder, said plug means producing no substantial pressure drop in air passing through said cylinder.