Abstract: An apparatus to directly take a sample of expired air from a subject which utilizes a stopper (3) with two distinct position. When the stopper (3) is in the upper position, it allows air blown in via the cannula (6) to scavenge the interior space of the tube (1) until the control (11,12, or 13) has indicated a sufficient volume. The cannula (6) is then pulled by the operator so that a blind stop (7) obturates the opening of an evacuation pipe (10) connected to the control. The stopper is then moved to a lower position to seal the sample of air in the tube (1).