You can do some research on the internet to satisfy your curiosity, but the questions (or the answers that you are looking for) are too specific for the forum.
Wiki has a nice article on Airport Security that you might want to look at:
Travelers are screened by metal detectors. Explosive detection machines used include X-ray machines and Puffer Machines. Explosive detection machines can also be used for both carry on and checked baggage. These detect volatile compounds given off from explosives using gas chromatography.
USMCFLYR