Ever since the September 11 terrorist attacks, federal agencies have been wishing for a system capable of issuing a nationwide alert at the first sign of a chemical, biological, or radiological attack. Now such a system is undergoing trials in Tennessee.

Developed by the U.S. Department of Energy's Oak Ridge National Laboratory in Tennessee, the new system consists of sensor packages attached to structures such as cell-phone towers. The packages will include detectors for airborne chemicals and radioisotopes, and for weather changes. The intent of the system -- which is being tested in Knoxville, Nashville, and other locations -- is to detect plumes of contaminants, predict their spread, and quickly alert command centers. In a 2002 test, prototype sensors successfully detected discharges of simulated sarin gas in three cities 140 to 270 kilometers apart and dispatched pertinent data in less than two minutes. The current trial will test the system on an even larger scale.