Mechem Explosive and Drug Detection System (MEDDS) is an odour-detection system involving vacuuming explosive odour from a suspect area onto a filter made from plasticized PVC (“mosquito netting”). Filters are made either by i) manual teams, who attach a filter to the end of a tube or “wand” of a portable backpack vacuum pump and pass the filter over the ground, or ii) mine-protected vehicles, where the filter is hung outside the vehicle.

The filter is transferred to a facility run as a laboratory for analysis by dogs. MEDDS uses a line of up to 10 filter stands, of which the first and last are “focus” filters. The dog works with a handler, whose role is to ensure that the dog is working properly and inspects every filter, and also to interpret the dog’s indication behaviour.

MEDDS uses as many as 6 dogs and they may run twice during the detection process for operational filters. One indication by either dog results in a suspect positive being returned. If no dog indicates on the filter, it is returned as a negative.