A.   Capabilities as a Vapor Detector

When conducting reconnaissance missions during Desert Storm, many Fox crews used the Air/Hi method, sampling airborne vapors instead of using the sampling wheels in the Wheel/Hi method. As stated earlier, the MM-1 is not a very sensitive vapor detector and, therefore, not a good system for determining areas of vapor contamination.

According to MM-1 experts at the US Army’s Soldier and Biological Chemical Command, the Fox is not well-suited for general vapor detection because the air volume drawn through the sampling probe is significantly less than the air volume drawn through other detectors, such as the M43A1 Chemical Agent Detector which is a component of the M8A1 Chemical Agent Alarm. The MM-1 draws approximately one milliliter of air per minute when hot[46] while the M43A1 draws approximately 1,000 milliliters of air per minute.[47] The result is that the MM-1 has about 1,000 times lower airflow than the M43A1.[48]

In 1994, the Defense Science Board published a report that compared the MM-1’s vapor sensitivities to other vapor detectors. Because the MM-1 calculates the minimum detectable amounts from the background sample, and because backgrounds vary depending on environmental and atmospheric conditions, the minimum detectable amounts for the MM-1 vary.[49] Table 5 lists each detector’s sensitivity to G-series nerve agents such as sarin.

Table 5. Vapor nerve agent detector characteristics[50]




Response Time
M43A1 G-series (includes sarin) 0.1-0.2 mg/m3 <=2 min
M256A1 Kit G-series (includes sarin) 0.005 mg/m3 15 min
CAM GB (sarin) <= 0.1 mg/m3 <=1 min
MM-1 GB (sarin) 62 mg/m3 <=45 sec

This sensitivity is the minimum concentration of agent vapor required for the detector to register for a positive detection or alarm. The minimum concentrations can be used to calculate whether the vapor present would physically affect unprotected exposed people. Vapor concentration is expressed in milligrams of agent per cubic meter of air (mg/m3). The effect a nerve agent vapor has on a person depends on the cumulative dose that person receives through breathing or absorption. "Dosage" refers to a cumulative exposure over time and is calculated by multiplying the amount of nerve agent concentration present by the length of exposure (mg•min/m3).[51]

At certain dosages, specific physical symptoms are expected. Studies conducted by the military determined specific dosages at which a person would exhibit symptoms of exposure to sarin nerve agent. At dosages of 1 mg•min/m3, personnel experience first noticeable physical effects such as miosis (contraction of the pupils accompanied by pain in and behind the eyes). The earliest effects on the respiratory tract are a runny nose, tightness in the chest, and, occasionally, prolonged wheezing.[52] The larger the dose, the more severe the effects. According to the toxicity data for sarin, a dosage of 35 mg•min/m3 is a median lethal dosage to 50 percent of exposed, unprotected personnel.[53]

Based on the concentration of 62 mg/m3 (noted by the Army and the Defense Science Board) for the MM-1 to indicate sarin presence, Table 6 summarizes the effects on personnel.

Table 6. Calculated dosages and their effects of a sarin vapor concentration of 62 mg/m3

Exposure Time



Effects on personnel

1 second

1.03 mg•min/m3

First Noticeable Effects
(1 mg•min/m3)

Exposed personnel manifest physical symptoms of nerve agent exposure

34 seconds

35.2 mg•min/m3

Median Lethal Dosage (35 mg•min/m3)

50% of unprotected, exposed personnel are fatalities

We calculated the dosages as follows:

The data in Table 6 shows that in an environment with a concentration of 62 mg/m3, within 34 seconds, half of unprotected, exposed personnel would become fatalities.

The available toxicity data and US Army sensitivity tests with the Fox in 1989 support the Defense Science Board conclusion, "When operating in the air sampling mode, the Fox is not a suitable warning device; very high concentrations of chemical warfare agents would have to be present, such that unprotected troops in the vicinity would be adversely and acutely affected."[54] This means battlefield casualties to unprotected exposed personnel would occur before the MM-1 could detect a chemical warfare agent vapor such as sarin. The Army MM-1 test and evaluation report made this point more concisely: the MM-1 "does not detect [chemical warfare agent] vapors to the danger level for humans."[55]

B.   Observations from Desert Storm

Commanders and MM-1 operators recognized the Fox’s improved detection capabilities during Operation Desert Storm. "The Fox Reconnaissance vehicle proved valuable to commanders by rapidly confirming that agents were not present."[56] However, there were some complaints.

C.  Lessons Learned

The operational urgency of the Desert Shield period accelerated the US acquisition plan for an NBC reconnaissance system. Although the Department of Defense tested the Fox in 1989 and wrote a very thorough report, it appears from several interviews conducted after the war that many US military personnel misunderstood the Fox’s capabilities and limitations. A common misunderstanding was overestimating the Fox’s ability to detect chemical warfare agent vapors. Planned improvements have been made including the addition of the Remote Sensing Chemical Agent Alarm (M21), a device that alarms to the presence of nerve and blister agent vapors from outside the boundaries of ground contamination. The M21 detects chemical agent hazards at line-of-sight distance up to five kilometers away.[61] Adding the M21 has improved the Fox’s vapor detection capabilities and provides more advance warning of a possible vapor chemical warfare agent hazard.

Before the Gulf War, no doctrine was written specifically for Fox use. US operators and crews trained rapidly at both the US Army Chemical School at Fort McClellan, Alabama, and the German NBC and Self Protection School in Sonthofen, Germany. Because so little time was available, training programs were inadequate, leaving operators without a foundation in basic chemistry and mass spectrometry techniques. Though the crews conducted a limited field exercise, the Gulf War mobilization-training program did not perform any certifying tests before operators deployed to Southwest Asia.[62] Since then, development of doctrinal publications and Fox operators training have steadily improved.[63] Today, the US Army provides more than 38 hours of MM-1 training and a certifying exam to operators.[64]

Another doctrinal deficiency was a lack of procedures to retain and archive the printed tapes resulting from the Fox’s wartime use. However, because some soldiers and Marines realized the tapes might be important for future use and kept them, we were able to use those tapes in subsequent Fox detection analyses.[65] According to current US Army doctrine, MM-1 crews must print the results of MM-1 analyses and transfer printed tapes to intelligence teams with samples taken at the site.[66]

During the Gulf War, it was not understood how contaminants affected the Fox (e.g., diesel fuel, vehicle exhaust, and burning oil well fire smoke). In situations when initial alarms sounded, it was critical for the operator to perform a spectrum analysis to determine more accurately the presence of suspected chemical warfare agents. The US Army is continually improving the MM-1 to better separate the chemicals sampled to more precisely identify chemical warfare agents in the presence of more common battlefield contaminants.[67]

Similarly, to improve the Vehicle Orientation System, the US Army is adding a Global Positioning System receiver to each Fox vehicle.

| First Page | Prev Page | Next Page |