Gas Chromatography Vial found in: Headspace Vials, Standard 22 x 38 Crimp Top, 2.0 mL Preassembled Vial Kits (8 mm/425 Screw-Thread, Unmarked Vials, Septa,.. crimp or screw thread finishes. The vials are used to heat the sample until the concentration of the liquid and gas phases are in equilibrium. phases are in equilibrium.