Chemical Agents

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I was the Distinguished Graduate of the March, 1967, Non-Commissioned Officer Chemical, Biological, and Radiological Warfare Class at the 7th Army Combined Arms School in Vilseck, Germany.

I still have my class notes, which I discovered while searching for information on the use of chemical agents in South Vietnam during my tour. While I am no chemist, or the ultimate source on chemical warfare information, I did function as the Chemical Warfare NCO for my battalion in Germany for over a year. In that capacity I was privy to information pertaining to the tactical use of chemical agents and the defense against them. The information offered below is intended as background information for those curious about the tactical use of and defense against all types of chemical agents.

Agent Classes

Chemical agents are divided into classes based on their purpose. These may be broadly categorized as Lethal War Agents, Non-lethal War Agents, Herbicides, equipment destruction agents, flame weapons, and smoke producing agents.

Equipment Destruction Agents
An example of an Equipment destruction agent is thermite. Thermite grenades are designed to destroy equipment. When ignited, thermite burns at an extremely high temperature. It has the ability to melt steel. Depending on the unit and mission, it was common for crews of armored fighting vehicles and self-propelled artillery to carry thermite grenades. The primary purpose was to destroy friendly equipment to deny its use to the enemy. A secondary purpose was to destroy captured enemy equipment.

Agent Orange is an example of a Herbicide. Herbicides were used to destroy foliage which provided the enemy with concealment. This agent was used extensively in South Vietnam, especially along roads to prevent the enemy from conducting concealed close-in ambushes.

Smoke Agents
Smoke generating agents were used mainly to mark locations of friendly and enemy units and to provide wind direction for landing aircraft. These agents could be employed via smoke grenades, which produced smoke by burning, smoke generators, and artillery rounds. One type of grenade which produced smoke was the white phosphorous grenade. This type of grenade exploded and showered a 5 meter area with burning chunks of white phosphorous. Artillery smoke rounds also contained white phosphorous.

Flame Weapons
Flame weapons contained thickened fuel, the military name for what is commonly referred to as "napalm". Thickened fuel was a combination of ordinary military grade gasoline (MoGas) and a powered thickening agent. The exact composition of this thickening agent was classified in 1967, but it is known that one of the components was an extract made from palm tree resin. The thickener caused the ignited fuel to stick to objects, including people. It produced a burn much worse that ordinary gasoline or a wood fire would produce. The extent of the resulting burn was deeper than burns caused by other sources. Personally, I believe flame weapons are much more hideous that any of the lethal chemical agents.

If I had a choice between being exposed to ignited thickened fuel or nerve agent, I would pick nerve agent. Death from asphyxiation in under 60 seconds is preferable in my mind to an agonizing, protracted death from thickened fuel-induced third degree burns over 90 percent of the body.

Thickened fuel could be dispensed in several ways. The most well known is the "napalm" canister which contains a small explosive charge which ignites the thickened fuel upon impact with the ground. Another well known dispenser was the PFT, or Portble Flame Thrower. This was a man-packed weapon with three tanks. Two tanks contained thickened fuel, while the third tank contained compressed air. The compressed air provided the propellant to put the fuel on target. An igniter in the muzzle of the weapon could be turned on or off to allow active flaming, or dispersal of unignited fuel. The latter technique was used against tunnel complexes in order to produce a buildup of unburned fuel which would descend into the lower reaches of a tunnel before being ignited.

There were two versions of the mechanized flame thrower. The more commonly known version was a modified M-113 armored personnel carrier which had a large fuel tank installed in the cargo compartment. The caliber 50 machine gun was usually replaced by the flame gun in the commander's cupolo. This vehicle was often referred to as a "Zippo Track". The other mechanized version was mounted in an M-48A3 tank. The flame gun was inserted into the bore of the 90mm gun-cannon and fired that way.

Thickened fuel was also used in defensive devices such as the flame trench and the flame fougasse. The former was a trench dug to a depth of 1 to 2 feet and filled with thickened fuel after a layer of det-chord and a number of 2-1/2 pound blocks of C-4 had been placed in the trench. The det-chord was connected to the charger from a claymore mine. The flame fougasse was a 55-gallon drum into which a single block of C-4 was placed in the bottom wrapped with det-chord. The det-chord was then wrapped around the top of the drum, just below the lid, and than connected to a claymore charger. The drum was filled with thickened fuel. When detonated, the device threw burning fuel about 50 meters at an attacking enemy. These were used extensively at fixed installations in Vietnam, especially small, isolated facilities such as pump stations.

Non-lethal Agents

Non-lethal agents included Riot Control Agents (tear gas), incapacitating agents, and vomiting agents. The purpose of this class of agent is to incapacitate the enemy and make it difficult for the enemy to carry out his mission. There were three types of agent in use in 1967.

Riot Control Agents
Two types of tear gas were in use by the military between 1966 and 1970: CS and CN. Of the two, CS was the more powerful. Although non-lethal by design, these agents could prove lethal depending on the physical condition of those exposed, and the environment in which the agent was used. For example, CS pumped into a tunnel could asphyxiate the occupants if enough agent was used and the occupants did not have protective masks.

Every soldier in the U.S. Army is exposed to CS during basic combat training. Further, CS was employed on a regular basis in training exercises in West Germany. The agent was used to simulate a lethal chemical agent attack, and practically every soldier who served in a line outfit was exposed repeatedly. The symptoms of CS exposure are unmistakable to anyone who has been exposed.

Incapacitating Agents
The U.S. inventory during 1966-1970 included one incapacitating agent which was referred to as BZ. This agent was designed to render an enemy unable to fight. It produced various symptoms which included, in some subjects, a tendency to fall asleep. It was therefore nicknamed "sleeping agent". The exact composition of this agent was not well known.

Vomiting Agents
DM was the nomenclature used to describe a vomiting agent. The sole purpose of a vomiting agent was to make it difficult for an individual to wear a protective mask. The vomiting agent was designed to be employed just prior to the use of a lethal chemical agent. The purpose was to produce an effect that would force the enemy soldier to remove his mask. With his mask removed, he became vulnerable to inhalation of the lethal agent.

Lethal War Agents

These agents are designed to kill and incapacitate. They are broadly broken down into four main categories. Blood Agents, Nerve Agents, Blister Agents, and Respiratory Agents.

Blood Agents
Blood agents are designed to interfere with the hemoglobin's ability to carry oxygen. They cause asphxiation. The primary blood agent was Cyanide vapor.

Blister Agents
Blister Agents are designed to cause casualties and not necessarily kill, although in high concentrations, or if inhaled, they can cause death. Blister agents contain powerful irritants which cause large, fluid filled blisters on exposed skin. These blisters break, making the exposed individual susceptable to infections, causing casualties. If inhaled, these agents cause blistering of the alveoli in the lungs. Mucous is secreted which, if exposure is severe enough, can cause the lungs to fill with mucous, causing death by dry land drowning. The primary blister agent was mustard vapor. Mustard agent is a highly persistent agent (see below). There are areas of France that are still contaminated by Mustard Agent that was sprayed by the Germans during World War One.

At the CBR NCO Course in Vilseck, Germany, all students were exposed to a diluted form of blister agent in the following exercise. While masked, each student had one drop of blister agent placed on each of three areas on the inside left forearm. One area had been prepared by applying the gray ointment contained in the tube from the M-17 Protective Mask carrying case. The remaining two areas were unprotected. One of these areas was then decontaminated using the gray ointment and the "pinch-blot" method of personal decontamination. The third area was left untreated. The next morning the results could be examined. Most men had only one fluid-filled blister about the size of a nickel. Some had two blisters indicating that their decontamination technique needed work. A few had three, indicating that they had not followed instructions with respect to preapplying the ointment. The blisters were painless and disappeared within two-three days if not broken. If broken and treated with ordinary antiseptic and covered with a bandaid there were no complications.

Respiratory Agents
Phosgene vapor was the primary respiratory agent. It caused severe buring of the alveoli in the lungs, reducing or eliminating the lungs ability to transfer oxygen to the blood stream. Mucous secreted by the body in response to these burns also caused dry land drowning.

Nerve Agents
Nerve Agents were divided into several classes, based on their volitility (also known as "persistence"), and their method of entry into the body. The categories were therefore persistent, non-persistent, percutaneous acting, and non-percutaneous acting.

Non-persistent agents are highly volitile, meaning that they evaporated relatively quickly. The specific mixture of the agent was dependent on the method used to deploy it. Examples of non-persistent agents were GA, GB, and GD. A non-persistent agent will not readily evaporate when used in a high-humidity environment, such as tropical rain forest or jungle. Nor will they readily evaporate when temperatures are low. This restricts their use in situations where friendly forces must occupy an intended objective.

Persistent agents have a very low volitility. They do not readily evaporate. They are designed for defensive use, and to deny use of specific areas to the enemy for long periods. Persistent agents are characterized by the oily nature of the dispersal medium. The only persistent agent in the U.S. arsenal between 1966 and 1970 was VX.

A non-percutaneous acting agent had to be breathed in order to enter the body. However, if an individual was exposed to sufficiently high concentrations of the agent, or if the exposed individual had open cuts or wounds, the agent could be absorbed in quantities sufficient to be lethal. However, tactical doctrine in 1967 maintained that the M-17 protective mask was sufficient protection from a non-percutaneous nerve agent, assuming the filters were relatively new.

All nerve agents are classifed as anticholinesterase agents. The term "nerve agent" is somewhat misleading in that the agent does not physically affect nerves per se. Instead the agent interfers with the central nervous system's ability to control muscle movement.

An Anticholinesterase agent attacks the enzymes that control messages between neural synapses and muscles. Acetylcholine is an enzyme which initiates muscle movement. Cholinesterase is an enzyme which is a solvent for acetylcholine, that is it dissolves it, causing an initiated muscle movement to cease. By attacking the enzyme Cholinesterase, the agent literally causes the muscles to work themselves to death. Since the diaphragm is the muscle controlling respiration, an individual usually dies of asphyxiation after exposure to the agent.

Further, the agent is not a gas, but rather a vapor. This is an important difference. If it were a gas (such as carbon monoxide) the M-17 Protective Mask issued to troops would not inhibit inhalation, since the M-17 allows gases (such as oxygen, which humans require to sustain life) through its filters. The M-17 Protective mask is designed to block airborne vapors.

A large number of household and garden pesticides contain an anticholinesterase agent.

Types of Nerve Agent

GA or "Tabun" was developed by the Soviet Union. It was classified as a non-persistent, non-percutaneous acting agent.

GB or "Sarin" was developed by the German firm I.G. Farben Fabrik in 1939. Sarin was an outgrowth of the company's research into pesticides. It was classified as a non-persistent, non-percutaneous acting agent.

GD, or "Soman" was classified as a non-persistent, non-percutaneous acting agent.

VX was classified as a persistent, percutaneous acting agent. VX was the most deadly of all the chemical agents.

Tactical Use

The following discussion assumes that the Rules Of Engagement specifically authorize the unit commander to use lethal battlefield chemical agents.

Lethal chemical agents are indescriminant. They kill friend and foe alike if used inappropriately. Extreme care must be exercised before the decision to employ these agents is made. Prior planning is essential to avoid casualties among friendly forces. All units in or near the area of intended use must be advised of the time, place, and type of agent to be employed well prior to the intended time of use.

There are a variety of factors that govern the tactical offensive use of lethal chemical agents. These include the Rules Of Engagement (ROE), temperature, humidity, wind speed and direction, terrain, the tactical situation, status of friendly forces' chemical defenses, status of enemy forces' chemical defenses, mission, time of day, potential negative impact on operations of friendly forces, and potential for enemy reaction.

All of these factors are important to the commander in the decision to employ lethal chemical agents on the battlefield. However the single most important factors are status of friendly forces' chemical defenses, and potential negative impact on operations of friendly forces.

Use of lethal or even non-lethal battlefield chemical agents in a situation where friendly forces do not have adequate training and equipment to protect themselves against these agents is obviously contraindicated. In this situation use of these agents would cause just as many, if not more, friendly casualties as enemy casualties.

The potential for negative impacts on operations of friendly forces includes the requirement that friendly forces must operate in protective masks. This tremendously reduces vision, as well as the ability to communicate over radios, and the ability to eat food and drink water. It also includes the contamination of equipment. Much effort would need to be expended in order to decontaminate equipment such as aircraft, armored fighting vehicles, personal weapons and equipment, and fixed fortifications and terrain, in order to prevent friendly forces from becoming casualties long after the initial use of the agent.

The denial of the use of territory is another potentially negative impact. Lethal chemical agents should not be employed in areas that are likely to be occupied immediately by friendly forces. The offensive use of these agents should not be directed at choke-points, since their use would reduce the mobility of friendly forces.

Defense Against Chemical Agents

The primary defense against chemical agents from 1966 onward was the M-17 protective mask. This mask was issued to all troops except armor crewmen and aircraft crewmen (who had a different type of mask which allowed them to plug into radios and the vehicle or aircraft filtration system). The M-17 protective mask was designed to protect the wearer against inhalation of airborne vapors. It utlizes two disposable, activated-charcoal, particulate filtering-membrane filters. These filters needed to be replaced after exposure to certain types of agent. The activated charcoal became saturated with agent after a certain level of exposure and ceased to function. Replacing the two filters was a tedious and time consuming process, and could not be accomplished while under a chemical attack.

Additional protection was provided by soaking fatigue clothing in a parafin-wax-based liquid. This reduced the permeability of the clothing but was considered a short term measure since the wax cracked at the elbows and knees. Also, this measure reduced the mobility of the soldier and was extrememly hazardous in hot climates due to the fact that it prevented the exhaust of sweat and retained body heat.

A third type of protection was the type of rubberized suit with self-contained breathing aparatus worn by workers in chemical factories. However this suit was completely unsuitable for combat use and none were issued to field units. These suits had all the liabilities of the parafin-dipped clothing.

Every M-17 protective mask, in every theater, was issued with three atropine autoinjectors, a tube of ointment designed to neutralize Mustard Agent, and a small supply of cotton patches designed to be used with the ointment in what was called the "pinch-blot method" for removing blister agents. These items were all stored in a pouch on the outside of the M-17 protective mask carrying case. Atropine was a routine item. The reason for this is fairly straightforward: since no advanced warning could be expected of an enemy chemical attack, the soldier had to be equipped with all of the available antidotes all the time. This was true for units in South Korea, West Germany, and Vietnam. While it is possible that units in the Continental United States (CONUS) would have removed these autoinjectors to prevent loss or inappropriate use, they were required by regulation in every theater where the potential for a surprise chemical attack existed.

The atropine autoinjectors were the main antidote for nerve agent exposure. If injected immediately, and assuming no reexposure occured, atropine was highly effective in countering the effects of nerve agent in most individuals. However, depending on the degree of exposure and the time elapsed between exposure and injection, the atropine may not be effective.

If injected outside the presence of an anticholinesterase agent, atropine produced an extremely dry, sticky mouth, but was otherwise harmless. It was very similar in effect to an antihistamine.

Steps to take if the presence of chemical agents is suspected:

1. Stop breathing
2. Mask
3. Give the alert "Gas! Gas! Gas!" outloud and over the radio.
4. Take the appropriate measures (e.g., inject atropine) for the agent suspected.
5. Send a ToxRep to higher headquarters as soon as possible. At a minimum, make sure to give the grid coordinates of suspected use, the type of agent (known or suspected), and the number of friendly casualties.
6. Continue the mission.
7. Remain masked until given the all clear by a superior officer.

When in doubt, mask!

Every U.S. Army soldier was required to be able to mask in ten seconds. In the presence of a lethal chemical agent, a soldier who took more than ten seconds to mask was a casualty, and probably dead. The saying in school was:

"The are two types of people on the battlefield: the quick, and the dead."


Decontaminating personnel and equipment is an arduous, time-consuming task that is essential if friendly casualties are to be avoided. Various slurry mixtures are provided to units as low as the company level and usually travel with the battalion trains. These slurry mixtures must be applied to vehicles and equipment and must then be washed off with copious amounts of water.

Any equipment that would be damaged by exposure to the slurry or water must be buried, preferably in a deep trench. This trench must be clearly marked using the NATO toxic agent markers. The eight-digit grid coordinates of this site must be recorded and transmitted to higher headquarters so that trained chemical decontamination personnel can, when the tactical situation permits, recover and properly destroy the contaminated equipment. Make no attempt to burn this equipment, even with thermite grenades, since it is possible that some unburned agent may be released and possibly cause friendly casualties.

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Creation Date: Saturday, July 4, 1998
Last Modified: Saturday, July 4, 1998
Copyright © Ray Smith, 1998