I think Paul's responses were pretty reasonable. These scanners are probably trying to pick up objects or things with organic compounds. I can't see the scanner going off for a material. otherwise clothes, underwear stockings etc would be setting off the machine. I think the machine is engineered to look for certain things, and organic compounds etc. I might be wrong.

If the machine did reveal a hair system, if there was no object or anything underneath that was of concern, I can't see why they would pull you aside. Kind of would defeat the purpose of the machine to me.