You must have a trust worthy face.
Got pulled over leaving Dubai a number of years ago, hands and rucksack came up positive on a random swabs test. Escorted into a back room for questioning. Luckily had photos of that morning activities at the Jebel Ali Shooting Club where I had been on the indoor range as well as the Skeet trap. Despite washing my hands they would probably be positive for the next week. Luckily the Security guys had a laugh.
Having said that, quite often get swabbed, Sydney in March, HK last October. Think I have an unlucky face, or a known profile!
