such as an exterior snap ring on the cylindrical portion of the plug which extends through the circular opening in the drawdown nut preferably the cylindrical portion of the plug is provided with a groove around its girth for mounting of the snap ring the apparatus is utilized by first evacuating the vial to a pressure of less than about 10 torr preferably between about 0 01 and about 1 torr such as about 0 1 torr the vial is easily evacuated by inserting a syringe needle through the rubber septum and into the vial and connecting the syringe needle to a vacuum pump drawing a vacuum in the vial and then removing the syringe needle while still drawing the vacuum by utilizing the cap and plug the evacuated device can be provided at most any location while retaining a pressure of less than about 10 torr in its interior volume at the survey site a sufficient amount of soil gas sample is injected with a syringe needle through the septum and into the vial to provide a positive pressure of between about 800 and about 4 000 torrs of soil gas for example where the vial has an interior volume of about 10 cubic centimeters a syringe having an interior volume of between about 20 and 50 cubic centimeters could be employed with good results for injection of soil gas into the vial once the sample has been injected the closure is positioned on the device to redundantly seal the interior from the environment the plug 35 is positioned with its frustoconical surface contacting the frustoconical surface of the tubular member and its annular flange contacting the annular flange of the drawdown nut the drawdown nut is threaded onto the tubular member.