C.  M256 Kit Maintenance

Maintenance of the M256 kit is a straightforward process in which no individual part ever needs adjustment or calibration. In addition to ensuring that the carrying case is not damaged and the shoulder/waist strap is not torn or frayed, M256 kit maintenance consists of the following actions: 1) ensure that each kit contains 12 vapor-samplers, one book of M8 detection paper, and one set of instruction cards; 2) check each vapor sampler’s discard date (expiration date) to ensure that the date has not passed or is about to pass; and 3) ensure that each vapor-sampler’s protective envelope is intact. An M256 kit that contains four or fewer vapor-samplers can be replaced or combined with another kit having fewer than four vapor-samplers. When M256 kits are combined, users should observe the discard date (expiration date) on each vapor-sampler’s envelope.[58] If a vapor-sampler’s discard date has passed (Figure 17), it must be replaced. The vapor-sampler should also be replaced if its protective envelope has been opened.[59]

fig17s.gif (21496 bytes)

Figure 17. Carrying case discard date statement (top) and vapor-sampler discard date (bottom)

Before using a vapor-sampler, the operator must ensure that the glass reagent ampoules, test spots, or the channels connecting them are not crushed, damaged, or missing. Before conducting a chemical agent test, operators must also check the blood agent test spot for the presence of any pink colored stain. If any one of these conditions exist, the operator should get another vapor-sampler or M256 kit.[60]



While the M256 kit is described as a miniature chemistry set, conducting a test on the battlefield is far different than conducting a test in a controlled laboratory. Consequently, the possibility that a substance found on the battlefield could cause the M256 kit to produce false detections must be considered.

Although the M256 kit is an improvement over older generation CWA detection kits, the M256 kit can produce false detections. False detections are of two types, positive and negative, with each having a vastly different outcome. A false positive detection occurs when the detector falsely indicates the presence of a CWA. False positive detections are considered an irritant or nuisance because they cause the extended and unnecessary wearing of the complete chemical protection suit, but do not lead to exposure to a CWA. A false negative detection, on the other hand, occurs when the detector falsely indicates that no chemical agent is present, when in fact it is present at or above the detector’s minimum detection level, possibly at a casualty producing concentration level. A false negative detection is serious because it can cause individuals to prematurely take off their mask and gloves, and thereby expose themselves to a CWA.

During the M256 development program, various prototype vapor-samplers underwent testing to identify substances that would produce false negative and false positive detections. During the testing, the M256 was exposed to vapors from chemical mixtures and compounds that could be found on a battlefield. The test results showed that none of the tested substances caused a false negative detection. However, several of the substances produced false positive detections. Specifically, smoke from burning brush, pyrotechnic smoke (HC), and dry supertropical bleach were found to produce false positive detections with some regularity.[61] Results of the battlefield interference tests are contained in the following tables. Table 4 lists the interferent element, the M256 vapor-sampler exposure test, and the test result. Table 5 lists the significant contaminants which caused false positive results (identified in table 4), shows the CWA that was falsely detected, the proportion of false responses to the number of tests, and the total proportion of false positive responses.  Unfortunately, neither the M256 kit operator's manual nor the Gulf War era chemical defense manuals clearly state the potential for false positive readings.

Table 4. M256 vapor-sampler battlefield interference test results[62]




In path of smoke from burning rubbish/brush M256 was placed down-wind in the path of the smoke. False positive for blood and blister

Exhaust fumes from one gasoline engine and one diesel engine

M256 was placed one meter (3.2 feet) downwind from two vehicles (one diesel and one gasoline) parked with engines running.

Small pink spots from oil in exhaust
Supertropical bleach slurry, high-test bleach slurry, calcium hypo-chlorite, and high-test hypochlorite M256 was placed five meters (16 feet) downwind from pans containing the decontaminants. False positive for lewisite, but only once
Supertropical bleach dry powder Some M256 vapor-samplers were exposed 3 or 4 inches above the powder for 10 minutes; some were exposed approximately 12 inches above the powder for 10 and 25 minutes False positive for lewisite and blister
CS (riot control agent) M256 was placed 75 meters (246 feet) downwind from one grenade for 10 minutes and from a second grenade for 15 additional minutes. No effect
Fumes from detonated explosive (TNT) M256 was placed downwind of fumes from the detonation of one pound of TNT. After a 10-minute exposure, a second pound was detonated. The M256 was exposed to fumes from the second explosion for 15 minutes. No effect
Fumes from burning explosives M256 was placed in the path of fumes from burning rifle powder, artillery propellant, and solid rocket propellant. After 10 minutes, additional quantities of rifle powder and artillery propellant were burned. The M256 was exposed to fumes from this second burning for 15 additional minutes. No effect
Fuel vapor from evaporating diesel fuel, gasoline, kerosene, motor oil, and antifreeze M256 was placed downwind from containers of the test substance. No effect
Fog oil smoke M256 was placed 25 meters (82 feet) downwind from 7 liters of burning oil. No effect
HC smoke (smoke grenade) M256 was placed 25 meters (82 feet) downwind from a functioning smoke grenade. One grenade was operated during the first 10 minutes and a second grenade was operated during the last 15 minutes. False positive for blood and blister
WP (white phosphorus) smoke M256 was placed in the path of WP smoke generated from phosphorus grenades. One grenade for the first 10 minute period and a second grenade for the subsequent 15 minute period. No effect
Decomposing waste M256 was placed near dead animals and human waste. The animals had been dead for at least two weeks. No effect
Colored smoke M256 was placed 25 meters (82 feet) downwind from red, yellow, green and violet smoke grenades. One grenade of each color was operated during the first 10-minute period and a second set of grenades was operated during the subsequent 15-minute period. No effect
Defoliants M256 was placed 25 meters (82 feet) downwind from a defoliant spraying operation. No effect
Dust M256 was placed in a chamber of blowing sand. Dust concentration was 1.8 grams per cubic meter. No effect
Salt Spray M256 was placed in a chamber and exposed to salt spray. No effect
Insecticide M256A1 was exposed to insecticide "Sevin." False positive when the eel enzyme disc contains less than 1.6 units of eel enzyme.[63]

Like the vapor-sampler, M8 detection paper has also undergone battlefield testing. The difference in testing was the substances used to conduct the test and the length of time for testing. Instead of vapors or aerosols, liquids were used to conduct each test. As a result of testing, several substances were found to cause M8 detection paper to produce a false positive indication. These interferents include: certain cleaning solvents (ammonia), Decontaminating Solution number 2 (DS2), "Break Free" (a weapons cleaner and lubricant), high temperatures, and some petroleum products.[64]

Table 5. M256 vapor-sampler significant battlefield contaminants (cause false positives)[65]

Interfering Material

Type of False Positive

Total Proportion of False Positive Responses

Smoke from burning brush





HC Smoke





Dry Super Tropical Bleach







Unlike the Fox NBC Reconnaissance Vehicle,[66] the M256 kit was already a standard item of NBC defense equipment at the start of the Gulf War, having entered the inventory in 1978.[67] Despite the years of acquisition and preparation, Gulf War era message traffic and unit after action reports indicate that some of the units that deployed to the Gulf may have had deficiencies in their NBC readiness posture.[68] These problems not only included the availability of equipment but also the availability of non-expired M256 kits. We also found requests for information concerning the reliability of the M256 kit. The requests primarily focused on the impact the desert environment would have on the M256 kit, the ability of the M256 kit to detect Iraqi CWAs, and the impact insecticide use would have on the M256 kit.

A.  M256 Availability

Shortages of M256 kits existed throughout the Gulf War period. The shortages surfaced as units prepared to deploy and continued throughout the war. As shown in the following excerpts, equipment shortages existed at all levels of command, in many types of units, and in both the Army and Marines:

The VII Corps Desert Storm/Desert Shield After Action Report indicates equipment shortages were not limited to any one unit:

…1CD [1st Cavalry Division] reported 60% of his M256 kits were expired and wanted to know if we could get replacements. …3AD Chem [3rd Armored Division Chemical] also reported 60% of his M256 kits were also expired. 3AD [3rd Armored Division] total shortage was 2600 and 1CD was short 115.[69]

…G-4 Rear, said there are 226 M256 kits on hand in Log Base Echo with 40 more due in. A total of 1250 were on order with no status. These had been released to 3AD.[70]

The logistical system for chemical defense equipment (CDE) was overtaxed due to lack of attention during peacetime. Upon arrival in theater, the division was short CDE, including M256 chemical agent detection kits, decontaminates,[sic] protective ensembles, and M8A1 chemical agent detector batteries.[71]

Additionally, the high number of requisitions submitted for M256 detector kits and M8… detection paper seem to confirm that unit accountability and management of these items were weak.[72]

Shortages of M256 kits were not confined to Army units; the Marine Corps also experienced shortages:

Having a limited supply of [both] M256 and M258 skin decontamination training kits forced ten to twelve Marines, rather than two Marines ("buddy system") to conduct the M256 test, and during hasty decontamination for Marines to "simulate" decontaminating the mask rather than actually doing it.[73] …the M256 detection kits weren’t available at the SIA [station of initial assignment], or [in] SWA [Southwest Asia] until late February. The shortage of M256 kits resulted in units like the 24th Marines not having any chemical detection capability other than the onset of symptoms.[74]

B.   M256 Reliability

During the early stages of the war, some of the M256 kits in the Kuwait Theater of Operations (KTO) were either approaching their expiration date or the date had already passed. Additionally, there was concern over what effect heat and humidity would have on expired M256 kits and, whether expired M256 kits could be used and how much trust could be placed in the test results.[75]

The US Army Central Command (ARCENT) responded to the heat and humidity concern in a message, "The M256 chemical detection kits will continue to function properly if they have not passed their five year shelf life."[76] This response shifted the focus from weather-related factors to that of using equipment beyond its intended shelf life.

As discussed earlier, when US troops began deploying to the Gulf, the M256 kit had a shelf life of five years. Many M256 kits that were initially shipped to the Gulf, during the early stages of the deployment period, were about to exceed their discard date or had already exceeded their discard date. Commanders were concerned that using M256 kits beyond their original five-year shelf life would produce unreliable test results. The Department of the Army’s Deputy Chief of Staff for Logistics responded to these concerns informing commanders that expired kits could be used, but he cautioned that expired kits had a tendency to produce false positives for nerve agent.[77] As mentioned earlier in this paper, if an expired kit produced a positive result for nerve agent, it was to be verified by conducting a second test using a vapor-sampler with a different lot number than the first or by using an alternate detection system such as an M8A1 chemical agent alarm or a Chemical Agent Monitor (CAM).[78] This was a temporary measure taken to ease the strain on the supply system.[79] No personnel were placed at increased risk by this action. It should be noted that the shelf life was formally extended from five to six years in January 1998.[80]

C.    Documentation of Incidents

During the war, just as today, a special type of operational report existed to report a suspected chemical attack and the actions that were taken in response to the suspected attack.[81] The purpose of these reports was to keep all levels of command as well as other units informed of the status of a suspected chemical attack. When received, each command level should have logged receipt of the report in their operations log and record the actions they took in response to the possible attack. Although not all unit logs and chronologies have been uncovered, the number of log entries that report events leading to increased MOPP levels and M256 testing for the presence of CWA’s, does not agree with the number of M256 tests being reported by some veterans.[82] This apparent discrepancy does not mean that suspected attacks went unreported or that M256 tests and test results went unreported. However, it is an indicator that some information may not have been logged in accordance with the regulatory/policy instructions that existed during the war for documenting events and incidents.

Accurately logging an event/incident provides an official record that is useful not only for the on-going operational mission, but also to allow after-action analysis of what happened. Unfortunately, during the Gulf War, log entries for incidents that resulted in M256 tests were not always complete or were never documented in the first place. Command elements that were notified of suspected attacks should have logged the receipt of these reports and any other information related to the incident, including any action(s) taken to resolve the reported incident. Because many of the M256 test results or details went unrecorded, important information regarding each incident may never be known.



The intent of this information paper is not to provide information on individual M256 detections. That is best left to the individual case narratives. The 11th Marines case narrative,[83] for instance, contains several discussions of incidents in which the initial M256 test produced a positive indication that could not be verified in subsequent tests.

Although many M256 kits were used during the Gulf War, the exact number of M256 detections may never be known. Some may have gone unreported while information about others is sketchy. A small number of M256 incidents have become known through congressional testimony and veteran interviews. To obtain more information about M256 detections and to respond to the recommendation of the Presidential Advisory Committee on Gulf War Veterans’ Illnesses (PAC), to investigate all M256 allegations, the Special Assistant initiated an M256 outreach effort in August 1997 to learn details of some incidents in which the M256 may have detected a CWA.

In August 1997 and again in May 1998, the Special Assistant sent letters to individuals who had been assigned to units that reportedly had an M256 detection during the war (see Table 6).[84] The units were known as a result of testimonies to Congress and the PAC. The letters notified recipients of our investigations and asked anyone with first-hand knowledge of an M256 incident to reply to our investigators. A total of 2,519 letters were mailed. As of May 15, 1999, 134 replies have reported 35 detections. Twenty of the 35 detections were reported either by individuals who claimed to have first-hand, eyewitness knowledge of an event or by the individual who operated the M256. Information from these responses (as well as information received from other sources) will be evaluated to determine an appropriate follow-up action, e.g., a new investigation, inclusion into an existing investigation, update to an existing case narrative, or no action required. One new investigation on M256 reports at Rafha is already in progress because of this outreach effort.

Table 6. Units identified for outreach

1st Battalion, 12th Marine Regiment Troop B, 5th Squadron, 6th Aviation Regiment
101 Airborne Headquarters and Headquarters Company, 101st Airborne Division Troop C, 5th Squadron, 6th Aviation Regiment
Headquarters and headquarters Company
101 Airborne Division Support Command
Troop D, 5th Squadron, 6th Aviation Regiment
Company A, 1st Battalion, 327th Infantry Brigade Headquarters and Headquarters Troop,
5th Squadron, 6th Aviation Regiment
Company B, 1st Battalion, 327th Infantry Brigade Headquarters and Headquarters Company,
101st Support Group
Company C, 1st Battalion, 327th Infantry Brigade Company A, 37th Engineer Battalion
Company D (Anti-Armor), 1st Battalion, 327th Infantry Brigade Battery B, 3rd Battalion, 8th Field Artillery Brigade
Headquarters and Headquarters Company, 1st Battalion, 327th Infantry Brigade Headquarters and Headquarters Detachment, 217th Maintenance Battalion
118th Military Police Company Company B, 37th Engineer Battalion



In addition to conducting investigations, the Special Assistant for Gulf War Illnesses is working to assure future force protection by disseminating information on problem areas identified during investigations. While conducting research for this information paper, three areas emerged as problem areas which need to be addressed. These problem areas are discussed in the following paragraphs.

The first problem area concerns the shelf life of the M256 kit. During the initial stages of the Gulf deployment, questions surfaced about the effectiveness of the M256 kits. These concerns arose not because the vapor-sampler was defective, but because many M256 kits arrived in the Gulf with expired discard dates or close to their expiration dates. This does not mean that good kits did not exist, only that they had not moved down the supply pipeline far enough or fast enough to be available at that time. In response to the immediate need, word went out that kits that had reached or exceeded their expiration dates could be used until replacement kits were received. This action, although there may have been no other alternatives, did not build confidence in expired vapor-samplers.

It would be easy to blame the supply system or suggest that if existing procedures had been followed there would not have been shortages. In reality, a combination of factors is likely to be responsible. Existing supplies must be monitored and new equipment ordered periodically to ensure adequate supplies are on-hand and that an adequate quantity is moving through the supply system. To ensure that chemical defense supplies are monitored, Congress, in 1994, directed the DoD to submit to Congress an annual assessment of NBC defense capability.[85] This report includes the current and projected supply status for individual pieces of chemical defense equipment, including the M256A1 kit. DoD’s latest Annual Report to Congress, dated March 1999, shows the risk assessment (probability that a shortage in the wartime requirement would exist) for the M256 kit as "low" but warns that shelf life expiration may reduce stocks in the future. The "low" risk assessment means that the "services have at least 85 percent of their wartime requirement on-hand to support two nearly simultaneous major theater wars."[86]

The second problem area concerns that of documentation. The number of M256 incidents reported to have occurred by veterans does not agree with the number of incidents that were recorded in unit logs and chronologies. Even though not all unit logs and chronologies have been uncovered that would definitively prove or disprove this theory, sufficient information has been uncovered to indicate that reporting and documenting incidents that resulted in the operation an M256 kit and the subsequent test result was inconsistent. More attention to proper and complete reporting, as well as the accurate recording of the results of M256 kit tests (positive or negative), would have been helpful in clarifying the rumors of chemical warfare attacks during the war, and would have been beneficial in post-event analysis.  In other words, it is important to report negative results as well as positive ones.

The third problem area involves communicating to operators the limitations of the M256 kit, namely that the M256 can produce false test results and the circumstances that can cause the M256 to produce false test results. This information is contained in documents that were produced during the research, development, test, and engineering phases of the M256 and M256A1 development programs. These documents provide a wealth of data to those people whose jobs are to develop equipment such as the M256 and M256A1, but the information, in this form, is not very useful (or usually available) to the individuals who have to operate the M256 on the battlefield. At some point, the information is filtered and condensed into the operator’s manual and training documents. Unfortunately, information regarding false positive and false negative detections was filtered to the statement "You may not be able to trust the test results."[87] Such a warning statement in the operator’s manual does not adequately convey the limitations contained in the original reference documents, the information contained in this information paper, or useful information for the battlefield decision-maker. Although no evidence has been uncovered to suggest that this omission placed individuals at an increased risk, at the very least, the M256 kit operator on the battlefield should know the limitations of the M256 kit.

This information topic remains open. Should additional information become available, it will be incorporated. If you have records, photographs, recollections, or find errors in the details reported, please call 1-800-497-6261.

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