Abstract: A plethysmograph is described that includes a reference chamber having a top wall, a bottom wall, a barrier wall spaced beneath the bottom wall, a continuous side wall having a lower edge, and a first continuous flange with a lower edge below the bottom wall and above the barrier wall; a test chamber having a bottom wall, a continuous side wall with an upper edge, and a second continuous flange extending upwardly from the upper edge, the interior face of one of the flanges including an annular groove with an O-ring in the groove, and the interior face of the other flange being tapered from vertical by up to about 1°; and a manifold having airflow openings in communication with the reference and test chamber and a common exterior airflow opening through a passageway, and a sampling port in communication with the passageway.

Abstract: A plethysmograph is described that includes a reference chamber having a top wall, a bottom wall, a barrier wall spaced beneath the bottom wall, a continuous side wall having a lower edge, and a first continuous flange with a lower edge below the bottom wall and above the barrier wall; a test chamber having a bottom wall, a continuous side wall with an upper edge, and a second continuous flange extending upwardly from the upper edge, the interior face of one of the flanges including an annular groove with an O-ring in the groove, and the interior face of the other flange being tapered from vertical by up to about 1°; and a manifold having airflow openings in communication with the reference and test chamber and a common exterior airflow opening through a passageway, and a sampling port in communication with the passageway.