A detection gate for detecting substances carried by an individual or an object, has two lateral uprights facing one another and defining a passage there between for the individual or the object, a blowing device installed in a blowing chamber in one of the uprights which are adapted to exhaust the air contained in the blowing chamber towards the other upright, an exhaust device installed in an exhaust chamber in the other upright, which are suitable for exhausting the air thus blown, a detection device arranged upstream from the passage and adapted to detect the presence of the substances in the air thus blown, and a transfer line which, via one of the ends thereof, leads into the blowing chamber and, via the other end thereof, into the exhaust chamber, the blowing device and the exhaust device being such that a single volume of air has time to pass through the passage at least twice during the time that individual or the object is present in the passage.