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by Jon Palfreman, producer,
Numerous detectors and alarms were used in the Gulf War to alert troops to the presence of chemical weapons. The trouble is that all can be 'set off' by other compounds, some of which are very common. The substances that cause false positives are called interferences.

  • One low-tec detections system is a chemically sensitive paper that servicemen wrap around their wrists and ankles. M8 and M9 paper changes color in the presence of nerve and blister agents. It also changes color in the presence of organic solvents like bug sprays.

  • Much more reliable is the M256A1 Chemical Agent Detector Kit, which enables the user to chemically test for chemical agent in both a vapor and liquid form. But even here, pesticides, smoke and strong bleach can produce false positives for sarin and mustard, so manuals require the test be repeated.

  • Throughout the war, the main chemical alarm used was the M8A1 Automatic Chemical Alarm. It was sensitive but not precise. Diesel exhaust, obscuring smoke and signal smoke can produce false positives.

  • The Chemical Agent Monitor (CAM) was used to find blister agent on the surfaces of vehicles and buildings. Interferences that give false positives include: after-shave, perfume, liquid cleaning solvents, signal smoke and burning fuels.

  • The top-of-the-line detector is the FOX NBC Reconnaissance System from Germany. These vehicles have an on-board mass spectrometer. Designed to scout the terrain ahead of the fighting troops, it uses a trailing wheel to sample the surface continually looking for chemical agents. The wheel touches against a probe and the on-board mass spectrometer makes a first "guess" as to what the substance might be.

Unfortunately, petroleum products can be mistaken for sarin in this preliminary analysis. Once a suspicious reading is obtained, the vehicle is supposed to stop, cool down its probe and carry out a full spectrum analysis to confirm the identity of the substance. Only if a full spectrum analysis is done can the operators be sure they have found a chemical agent and not an interference. During the Gulf War, many of the Fox vehicles drove along with tank convoys and did not have time to carry out the full analysis to confirm, or reject, their prelimenary findings.


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