A. The Fox Vehicle
The US Army field manual on the Fox states, "The Fox is a dedicated system of NBC detection, warning, and sampling equipment integrated into a high speed, high mobility, wheeled, armored carrier capable of performing NBC reconnaissance on primary, secondary, or cross-country routes throughout the battlefield." The Fox vehicle travels quickly enough to keep up with maneuver forces. An overpressure system pressurizes and seals the vehicle to protect the crew from outside contamination and allow the crew to conduct NBC reconnaissance, retrieve and retain samples for laboratory analysis, and outline contamination boundaries with visual markers, all without leaving the vehicle or wearing protective clothing. A Vehicle Orientation System (VOS) provides position location information to the crew and allows them to report areas of possible chemical contamination. An on-board air conditioner keeps electronic equipment from overheating. Figure 2 shows key features of the Fox vehicle.
Figure 2. Fox NBC Reconnaissance Vehicle key features
B. Detection Equipment
The Fox has several on-board NBC detection systems and devices, including:
The Fox does not provide any biological hazard detection capability, but the overpressure system protects the crew from biological hazards.
C. The MM-1 Mobile Mass Spectrometer
The MM-1 Mobile Mass Spectrometer is the heart of the Fox detection system. Located inside the vehicle, it analyzes air or ground samples for the presence of possible liquid chemical warfare agents by drawing air through the air/surface sampler positioned on the outside of the vehicle to the MM-1 detection unit which analyzes the substance and displays the results on a video screen. A mass spectrometer uses energy to fragment chemicals contained in the samples into measurable ions that are indicative of the original molecule. Every chemical has a characteristic combination of ions, identified by their mass and relative intensity, known as a spectrum. The resulting spectrum can be used to identify the substance.
The MM-1 contains a pre-programmed library of 60 chemical compounds, including common chemical warfare agents and some common precursor and chemical breakdown products. From this library, the MM-1 continuously monitors an initial list of up to 22 chemical compounds, which are based on the suspected or likely chemical warfare agent threat. The library contains the characteristics of the four most significant ions for each of the 60 chemical compounds. The MM-1 compares the known ion combinations in its library to the samples ions. The MM-1 also compares the three lesser ions relative intensities to the intensity of the most prevalent ion, usually set at a relative intensity of 100%. When analyzing a sample, the MM-1 signals a warning or alarm if the sample contains ions sufficiently similar and at an appropriate intensity similar to a chemical in the MM-1s library. The MM-1s alarm continues until either the ion intensity level falls below the alarm level, the MM-1 operator changes sampling methods or restarts the Fox MM-1. Tab C lists the 60-substance chemical library programmed into the MM-1 during the Gulf War.
The MM-1 does not measure a samples chemical concentration but compares a samples ion levels against the chemical compound ions present in uncontaminated airthe background sample. At the start of each mission, the MM-1 operator takes a background sample, from which the MM-1 computes a minimum detectable amount for each chemical in its library. When the MM-1 processes a sample with ions similar to a chemical in its library, it calculates whether the sample exceeds this minimum detectable amount. The MM-1 sends a warning if a sample chemical is above this level by a predetermined amount and alarms at a second higher predetermined relative intensity. During Desert Storm, the MM-1 issued a warning at a relative intensity value of 0.6 above the minimum detectable amount and an alarm at a relative intensity value of 0.9 above that level. In other words, if the minimum detectable amount was 3.0, the MM-1 would issue a warning at a relative intensity of at least 3.6 and would sound an alarm at 3.9 or above.
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