At airports around the world, the question “What’s inside that bag?” is answered thousands of times a day, to detect explosives, poison, chemical compounds,… in both carry on and checked in luggage.
Checking all those bags, trolleys and suitcases by hand would be too much work and might also be dangerous, so thank god for CT-scanners.
Using x-rays, it’s possible to see the content of the bags without opening them and thanks to some smart technology, it’s even possible to distinguish a difference between organic, inorganic or metal objects because of a difference in density and amount of radiation the objects absorb.
Most bombs are made from organic material, but most organic objects are low-energy, so for this reason, the rays from the scanner are passed through 2 detectors: first through a full detector, then through a high-pass filter to filter out the low energy signatures and then through the second filter. The software automatically compares the data from both detectors and the differences between them are the low energy objects, most often the organic material.
I’m sure most of us have heard stories about camera’s not working after passing through a scanner at the airport, laptops that stop functioning,…
These are however myths if those objects are in the carry on luggage. The scanners used at the security checkpoints are what they call “film-safe”. The amount of radiation is so low there will be no effect what so ever on film or electronic devices.
If however you put your camera in you checked bag, there is the possibility of damage. The checked luggage is often processed in larger batches, with more powerful equipment, higher levels of radiation and so more effect on the film. Laptops and other electronic devices should however be safe with the latest technology.
This is once again a great way NDT makes our lives easier. It is however interesting to note that this isn’t the best bomb detection method available. Most airports still have a dedicated staff of trained dogs to sniff out suspicious items, often with a higher success ratio than modern technology research has found.
No matter how good technology is, nature still does it better.
For more information about how the scanners at airports work and what other methods are used check out this link