What constitutes explosive residue? One reason for asking is ever since I had a heart blockage in 2000 resolved by inserting a stent to keep the blockage open, I have carried nitroglycerin tablets. I've never needed to use one but they are with me. With all the shaking during travel, the tablets often turn to powder. In addition the bottle cap often comes off and the powder is distributed around my pocket, backpack, or wherever I happen to be carrying them. In an explosive residue test would nitro tablets, carried by thousands of Americans, show as an explosive residue? Now that I'm retired my hobby is farming and one of the products I use is ammonium nitrate fertilizer. It ends up on my clothes and I'm not sure washing removes all traces. Will this also result in explosive residue? I have only heard of explosive residue being found - has there ever been further identification of the exact residue to verify it is from an explosive device being detonated? There has been a lot of finite evidence released regarding a fire.