In the experimental phase, the decoy boxes would hold sweat samples collected from COPD patients instead of naïve T-shirts. The dogs would be asked to locate boxes containing the T-shirt sample taken from the lung cancer patients, from the decoy boxes. Every sequence will include 4 boxes with a different ratio between the specimens (each time a different number of boxes will contain samples taken from cancer patients, 0,1,2,3 or 4 when the rest of the boxes would contain samples collected from COPD patients). The dogs would mark the specimen by sitting next to each relevant box (they will ignore the decoy boxes after sniffing them and identifying them as irrelevant).