EPA (VOA/VOC) Sampling Vials. 40ml EPA Vials have long been the vial of choice for volatile organic (VOA/VOC) sampling and analysis. Our extensive range of sampling vials also includes 20ml and 30ml vials, available in clear or amber glass. Vials are available with a Hole-Cap & Septa for use with autosamplers, Solid Cap & Liner for transport