Abstract: A tube assembly includes an inner tube telescoped into an outer tube. The inner tube is dimensioned to define a substantially annular space between the inner and outer tubes. Portions of the inner tube near its open top are configured to permit venting as the inner tube is inserted into the open top. However, the vent is closed during insertion of a closure into the tube assembly or prior to inserting a closure into the tube assembly.

Abstract: The present invention is directed to a retention mechanism for retaining a stopper on a test tube during pressure differentials, as well as a securing element for use therein. The retention mechanism includes a securing element for inhibiting strain between the stopper and the test tube. The present invention is also directed to a method of retaining a stopper on a test tube during pressure differentials. The method includes providing at least one adjustable retaining element and maintaining a force between a first portion and a second portion to maintain the stopper in fixed relation to the top end of the test tube.