These guys check everything, I was carrying my guitar through Logan about 11 years ago coming the Philippines and the case was lined with Anhydrous copper sulfate. The chemical is used as a drying agent and keeps my guitar rust free. It also has a distinct smell, so the customs occifer was kind enough to ask me to open the guitar case and then proceeded to rip it to shreds he then completely took apart my guitar, and was too f#cking lazy to put it back together so not only did I miss my connecting flight, but I had to carry my guitar in a dozen pieces around the airport for the next couple of hours.