LESSON 1
FUNDAMENTAL ASPECTS OF CHEMICAL AGENTS
Critical Task: 031-506-2002
OVERVIEW
LESSON DESCRIPTION:
In this lesson you will learn the description of fundamental aspects of chemical agents.
TERMINAL LEARNING OBJECTIVE:
| ACTION: | Describe fundamental aspects of chemical agents. |
| CONDITION: | Given information and illustrations about chemical agent terms, properties, classification, duration of effectiveness, and markings for chemical munitions. |
| STANDARD: | Demonstrate competency of the task skills and knowledge by responding to the multiple-choice test covering chemical agent terms, properties, classification, duration of effectiveness, and markings for chemical munitions. |
| REFERENCES: | FM 3-6, FM 3-8, FM 3-9, FM 3-10 and STP 3-54B2-SM. |
INTRODUCTION
An aggressor's perception of United States unpreparedness for chemical warfare may lead to testing this perception in combat. If this occurs, the skills and dedication of soldiers, staffs, and commanders will be severely tried by an enemy possessing an overwhelming numerical superiority. Chemical agents may be employed by any force to develop additional combat power. Chemical agents may, if properly employed, do much toward neutralizing any numerical advantage the enemy may have, reduce the effectiveness of combat formations, disrupt rear area operations and troop movements, restrict the use of key terrain and reduce the combat efficiency of troops. Chemical agents give commanders options that vary from mild incapacitation, lasting a few hours, to serious illness and injury requiring months of treatment and convalescence, or death. These effects, depending upon the agent selected, may be produced immediately, in a few minutes to an hour, or they may be delayed for several hours. At the same time, chemical agents may be used in combination with other agents or with conventional weapons, disguising and/or complementing the effects of one or both systems.
As a prerequisite for understanding chemical agents, you must have a working knowledge of the terms used in describing chemical agents. The more commonly used terms are explained as they apply to military chemistry and chemical agents. The following is a good reference to enhance understanding of the terms used in the subcourse.
1. Aerosol. A liquid or solid, composed of finely divided particles, suspended in a gaseous medium. Examples of common aerosols are mist, fog, and smoke.
3. Chemical Agent. A chemical compound which, through its chemical properties, produces lethal or damaging effects on man. Excluded from consideration are riot control agents, chemical herbicides, and smoke and flame materials.
4. Chemical Agent Casualty. A person who has been affected sufficiently by a chemical agent to prevent or seriously degrade the ability to carry out the mission.
5. Chemical Agent Symbol. The US Army code designation of any chemical agent. This is a combination of one to three letters or letter/number combinations; it should not be confused with the chemical formula.
6. Chemical Compounds. Chemical mixtures which are not intended to produce lethal or damaging effects on human beings. Included in this group are riot control agents, herbicides, and smoke and flame materials.
7. Chemical Contamination. The presence of a chemical agent on a person, object or area. Contamination density of a chemical agent is usually expressed either in milligrams or grams per square meter (mg/m2, g/m2 ) or in pounds per hectare (lb/ha). A hectare is 10,000 square meters.
8. Chemical Weapons System. An integrated relationship of chemical agents, munitions, or spraying devices and their mode of delivery to the target.
9. Concentration. The amount of a chemical agent present in a unit volume of air. Usually expressed in milligrams per cubic meter (mg/m3) of air.
10. Decontaminating Material. Any substance used to chemically destroy, physically remove, seal, or otherwise make a chemical agent harmless.
11. Detection. The determination of the presence of a chemical agent.
12. Dosage (Ct). The concentration of a chemical agent in the atmosphere (C) multiplied by the time (t) the concentration remains, expressed as mg-min/m3 or the cumulative exposure equivalent to the concentration of chemical agents to which and individual is exposed, integrated over the time of exposure. The dosage received by a person depends upon how long the person is exposed to the concentration. That is, the respiratory dosage in mg-min/m3 is equal to the time in minutes an individual is unmasked in an agent cloud multiplied by the concentration of the cloud. The skin dosage is equal to the time of exposure in minutes of an individual's unprotected skin multiplied by the concentration of the agent cloud. (This is generally understood as being the effect upon the whole body.) The physiological effectiveness of skin and respiratory aerosol dosages are influenced by particle size as well as time and concentration, since retention by the lungs and impingement upon the skin are functions of particle size. They are usually expressed in mg-min/m3 for a particle size.
13. Liquid Dosage. The weight of liquid agent received by a person on the skin is usually expressed as dosage in milligrams of contaminant per kilogram (kg) of body weight (mg/kg). This is equivalent to parts per million.
14. Restrictions. Actually, an individual may show signs and symptoms after exposure to a chemical agent which are less or more than expected for a given dosage (Ct), depending upon some of the following variables:
a. How long the breath was held during short exposure.
b. Speed with which mask was donned.
c. Ability to fit mask and mask leakage factors.
d. Whether the chemical agent was also absorbed through the skin.
e. Whether the chemical agent stimulated the rate of breathing.
f. Rate and depth of breathing of the individual at time of exposure.
g. Amount of physical exertion of the individual at time of exposure.
h. Rate of detoxification, especially if exposure was long. For tabulation purposes, such variables are ignored, and the Ct values are assumed to measure the amount of chemical agent received by an individual breathing at a normal rate in a temperature climate with average humidity. These values provide a basis of comparison for the chemical agent.
15. Harassing Concentration. A concentration of a chemical agent which requires masking or other protective measures. Such concentrations may be insufficient to kill, but sufficient to interfere with normal operations.
16. Identification. Can be subdivided into two levels of identification as follows:
a. Definitive identification is the determination of the exact identity of a compound through the establishment of a group of unique characteristics.
b. Classification is the determination that a compound is a member of a class of substances without knowledge of the exact identity of the compound.
17. Lethal Chemical Agent. An agent that may be used effectively in field concentrations to produce death.
18. Oxime. 2-PAM Chloride (trade name Protopam Chloride or Pralidoxime Chloride) used in treatment of nerve agent poisoning by some, but not all, cholinesterase inhibitors (nerve agents). Unlike Atropine, it acts by reactivating the inhibited enzyme of the skeletal muscles as well as the parasympathetic (glands and intestinal tract) sites, and therefore relieves the skeletal neuromuscular block which causes the paralysis associated with the nerve agents.
19. Persistency. An expression of the duration of effectiveness of a chemical agent. This is dependent on physical and chemical properties of the agent, weather, methods of dissemination, and conditions of terrain. Persistent and Nonpersistent should not be used to denote classes of chemical agents.
20. Physostigmine. An alkaloid from Physostigma venonosum. Physostigmine salicylate is used to relieve symptoms of BZ and other glycollate casualties.
21. Toxicity. The property possessed by a material which enables it to injure the physiological mechanism of at organism by chemical means, with the maximum effect being incapacitation or death.
23. Training Agent. An agent authorized for use in training to enhance proficiency for operating in a chemical environment.
24. Vesicant Agent. An agent which acts on the eyes and lungs and blisters the skin.
25. Warning. The timely dissemination of the information that a chemical agent is present or anticipated.
26. Monitoring. The continued or periodic act of seeking to determine whether a chemical agent is in the area.
27. Survey. The directed effort to determine the location and nature of the chemical agent in an area.
28. On-target Attack. Chemical agents are delivered directly into the target area where a position is the target for a direct attack by one or more chemical agents delivered either by air or ground means.
29. Off-target Attack. Residual chemical agent clouds drift onto positions or where personnel moving across country encounter toxic clouds or surface contamination.
30. Median Lethal Dosage (LCt50). The LCt50 of a chemical agent is the dosage (vapor concentration of the agent multiplied by the time exposure) that is lethal to 50 percent of exposed unprotected personnel at some given breathing rate. The unit used to express LCt50 is mg-min/m3.
31. Median Incapacitating Dosage (ICt50) The ICt50 of a chemical agent is the amount of inhale vapor that is sufficient to disable 50 percent of expressed unprotected personnel. The unit to express ICt50 is mg-min/m3.
PART B - CHEMICAL AGENT REQUIREMENTS
A discussion of chemical agents would be incomplete without an understanding of what makes a substance a chemical agent and the features desired in a chemical agent.
1. Chemical Agent Requirements. The following are the requirements of a chemical agent:
- It must possess toxicity. Through its chemical properties, it will produce lethal and damaging effects on man, animal or plant.
- It must also be capable of accomplishing the mission for which it is employed.
- It must be stable or capable of being stabilized during the period of time between its production and use.
- It must be procurable from available raw materials in the quantity required for effective military use.
- It must be capable of being disseminated from a device practicable for field use in sufficient concentration to produce the desired effect on the target.
- It must be capable of being handled and transported, provided proper precautions are observed.
2. Desirable Features. The following are desirable additional features of a chemical agent:
- It should have little or no corrosive action on the munition or container during storage.
- It should possess such inherent properties that complete protection from the chemical agent is difficult for enemy personnel. If possible, the agent should be capable of minimizing the effectiveness of the protective equipment of potential enemies.
- The agent's mechanism of action, protective measures, and method of treatment should be known.
- It should be difficult to detect by ordinary methods prior to the time of onset of physiological and/or psychological effects. Colorless, odorless, and nonirritating toxic chemical agents are desirable.
3. Classification. Once you understand the features of a chemical agent, the next step is classifying chemical agents and miscellaneous related compounds. Chemical agents and chemical compounds are classified according to: physical state (including degree of volatility), use, and physiological action. Persistent and nonpersistent are terms used to describe the tactical use of chemical agents and should not be used as terms to technically classify them.
a. Physical State. Chemical agents and chemical compounds may exist as solids, liquids, or gases. To a certain extent the state in which an agent normally exists determines its use, duration of effectiveness, physiological action, and the type of munition used for its dissemination.
b. Chemical Agent Use. Chemical agents may be grouped according to use as follows:
(1) Toxic Chemical Agents. Agents capable of producing incapacitation, serious injury, or death when used in field concentrations.
(2) Incapacitating Agents. Agents that produce physiological or mental effects, or both that may persist for hours or days after exposure, rendering individuals incapable of concerted effort in the performance of their assigned duties. Complete recovery of incapacitating agent casualties is expected without medical treatment. (See Table 2-1.)
c. Chemical Compound Use. Chemical compounds may be grouped according to use as follows:
(1) Training Agents and Compounds. Authorized for training.
(2) Screening and Signaling Smokes. Screening smokes are compounds that produce an obscuring smoke when burned hydrolyzed, or atomized; they are used to limit observation and to reduce the effectiveness of aimed fire. Signaling smokes are similar to screening smokes, except that signaling smokes generally are colored and are used for visual communication. The standard colors are green, red, violet and yellow.
d. Physiological Action. Physiological actions of chemical agents are described below.
(2) Nerve Agents. Chemical agents which, when absorbed into the body by inhalation, ingestion, or through the skin, affect the body functions by reacting with an enzyme (cholinesterase) throughout the body, permitting accumulation of a stimulator (acetylcholine). The major effects are those on the voluntary nervous system, e.g., muscle stimulation with uncoordinated contractions; followed by fatigue and eventual paralysis; those on the parasympathetic nervous system, e.g., pinpointed pupils; bronchial constriction; nausea, vomiting, and diarrhea; secretion of the glands of the nose, mouth, bronchi, and gastrointestinal system; and those on the central nervous system, e.g., disturbances in thought, convulsions, coma, and lethal depression of the vital centers of the brain.
(4) Vomiting Agents. Compounds causing vomiting may also cause coughing, sneezing, pain in the nose and throat, nasal discharge, tears, as well as headache often following.
(5) Blister Agents. Chemical agents that are readily absorbed by both exterior and interior parts of the body, causing inflammation, blisters, and general destruction of tissues. Besides affecting the skin, the agent vapors attack the respiratory tract with the effects usually more severe in the upper tract. Eyes are very susceptible to blister agents.
(6) Tear Agents. Compounds causing a large flow of tears and intense, although temporary, eye pain when used in normal field concentrations. The tear agent CS is very irritating to the respiratory tract mucosa, causing the sensation of difficulty in respiration. In high concentrations, tear compounds are irritating to the skin and cause a temporary burning and itching sensation. High concentrations can also cause burns, nausea, and vomiting.
4. Duration of Effectiveness of Chemical Agents. Factors that determine the duration of time a chemical agent exists at the point of dissemination are:
a. Physical Properties of the Agent. Volatility is one physical property that is especially important in determining the duration of effectiveness of an agent. Viscosity is another important property.
b. Weather Conditions. Temperature, temperature gradient, wind speed, and precipitation are the most important weather factors in determining duration of effectiveness.
c. Methods of Dissemination. The state of physical division greatly influences the effectiveness of agents which are normally liquid or solid. In explosive munitions, the degree of division is dependent upon the amount and type of burster charge and upon the fuzing of the munition (air or ground burst). Nonexploding types of munition, such as aerosol generators and spray tanks, are devices for varying the degree of dispersion and thus influencing the duration of effectiveness of chemical agents.
d. Conditions of Terrain or Target. Vegetation, soil, and buildings play an important part in the duration of effectiveness of a chemical agent at the point of release.
PART C - CHEMICAL MUNITIONS MARKINGS
- Current stockpiles of chemical and related munitions contain a high percentage of munitions manufactured prior to January 1961, as well as those manufactured since.
- Personnel engaged in operations in former training and range areas may encounter munitions marked using each system.
2. A working knowledge of each system is necessary to correctly identify munitions and therefore determine the associated hazards. The Five-Element Marking System (Old), prior to January 1961, the Standard Color Coding System (New), after January 1961, and the Revised Color Coding System (1976) are described in the following paragraphs.
a. Five-element Marking System (Old). All chemical munitions manufactured before January 1961 follow the Five-Element Marking System. According to this system, all chemical munitions are marked with a gray background. One band around the munition indicates a nonpersistent effect agent and two bands indicate a persistent effect agent. Green marking on the gray background signifies toxic chemical agents and red marking signifies irritant agents. A descriptive word such as gas indicates the general nature of the agent. A chemical agent symbol (GB, VX, HD) indicates the exact filling. Additional information on chemical munitions is given in the following technical manuals: TM 9-1901-1, TM 9-1300-202, TM 9-1325-200, and TM 43-0001-26-1. The Five-Element Marking System of marking chemical munitions at the present is shown in Figure 1-1.
b. Standard Color Coding System (New). The Standard Color Coding System of marking chemical munitions at the present is shown in Figure 1-2.
c. Revised Color Coding System (1976). Munitions manufactured after 1976 are marked according to the Revised Color Coding System (1976) shown in Figure 1-3.
All chemical munitions manufactured prior to January 1961 will retain their original color code markings. |
3. Chemical Compounds. Chemical compounds, to include toxic chemical agents (casualty agents) and incapacitating agents, are indicated by a gray background with appropriate bands to indicate the persistency of the filling. The presence of a high or low explosive charge is indicated by a yellow or brown band, respectively, in addition to the appropriate chemical substance markings.
a. Toxic Chemical Agents. Gray background with green bands; one band for nonpersistent agents, two bands for persistent agents, and three for nerve agents.
b. Incapacitating Agents. Gray background with red bands; one band for nonpersistent agents and two bands for persistent agents.
Figure 1-1. Five-Element Marking System (Old)
Figure 1-2. Standard Color Coding System (New)
Figure 1-3. Revised Color Coding System (1976)
GO TO:
