In addition to passenger baggage, most planes carry enormous amounts of cargo. All of this cargo has to be checked before it is loaded.
Most airports use one of three systems to do this:
- Medium X-ray systems - These are fixed systems that can scan an entire pallet of cargo for suspicious items.
- Mobile X-ray systems - A large truck carries a complete X-ray scanning system. The truck drives very slowly beside another, stopped truck to scan the entire contents of that truck for suspicious items.
- Fixed-site systems - This is an entire building that is basically one huge X-ray scanner. A tractor-trailer is pulled into the building and the entire truck is scanned at one time.
One old-fashioned method of bomb detection still works as well or better than most hi-tech systems -- the use of trained dogs. These special dogs, called K-9 units, have been trained to sniff out the specific odors emitted by chemicals that are used to make bombs, as well the odors of other items such as drugs. Incredibly fast and accurate, a K-9 barks at a suspicious bag or package, alerting the human companion that this item needs to be investigated.
In addition to an X-ray system, many airports also use larger scanners. Let's take a look at those next.