Sensors in sewage tunnels can help identify source of homemade bombs

Law enforcement may someday identify the source of homemade bombs using an unorthodox method -- monitoring sewage tunnels.

Swedish scientists have developed a system to detect the production of explosives in urban areas. The system is called the Explosive Material Production Hidden Agile Search and Intelligence System (EMPHASIS), and is developed by the Swedish Defense Research Agency (FOI). The organization says its goal is to pinpoint so-called bomb factories by narrowing down the search area.

The FOI says the system could prevent future terrorist attacks, and cites tragedies like the London, Bali and Madrid bombings.

EMPHASIS works by using a network of sensors above ground and in sewage tunnels to detect explosives or precursors to explosives in the air or in liquid waste. The data collected will go to a command center. If elevated amounts of suspicious chemicals are detected in high concentration levels, information about the type of substance, location, time and amount will be noted for evaluation.

According to New Scientist, the underground sensors are 10-centemeter-long devices called ion-selective electrodes. The devices are submerged in waste water, where it can detect changes in voltage that are caused ions found in the chemicals. The scientists will use software to find patterns in the concentration of ions.

In the air, lasers will be used to detect gas vapors that travel out of windows where explosives or precursors are vented out. The static sensors can monitor distances of 100 to 400 meters.

The scientists say they have successfully tested the sensors in the lab and will test the devices in real sewers next year.