Discussion 6
Chemical Agents and Explosives
A. History of Chemical Weapons
Chemical hazards may be divided into two broad categories, that is, those from
dedicated chemical weapons agents and those from toxic industrial chemicals. Both have
the capacity to inflict injury and kill biota, and both occur in massive quantities
worldwide. The two categories differ in many ways; for example, toxic industrial
chemicals tend to be commercially available, whereas chemical weapons are kept under
heavy guard and are considered hardened targets. Due to the possibility of chemical agent
use in future military conflicts and/or terrorist attacks, response agencies (police, fire,
emergency medical services) as well as military personnel must possess accurate
knowledge of these agents, their effects, and the appropriate methods for treating
casualties.
Nations have waged war via chemical means for millennia. Archeological
evidence from civilizations in Egypt, Babylon, India, China, and elsewhere has revealed
the application of chemical warfare in ancient and classical times. With each new armed
confrontation between warring parties, weapons have evolved to become more innovative
and lethal than were previously Chemical warfare appears to have been highly developed
by the ancient Chinese. Some historians have proposed that the development of chemical
weapons originated from the fumigation of Chinese dwellings to eliminate fleas, which
was practiced as far back as the seventh century b.c.e.
Early Chinese writings contain hundreds of recipes for the production of
poisonous or irritating smokes for use in war along with accounts of their success. The
use of arsenic trioxide smoke is mentioned in early Chinese manuscripts. Accounts from
the Mohist sect in China (fourth century b.c.e.) describe the use of ox-hide bellows to
pump smoke from burning balls of mustard and other toxic plants into tunnels under
construction by a besieging army. One of the first known riot control agents involved the
use of finely divided lime dispersed into the air to suppress a peasant revolt in c.e. 178.
The use of irritating five-league fog, formed from a slow-burning black powder to which
varied ingredients, including wolf excrement, was added to produce an irritating smoke,
is recorded. Much later, the use of poisonous gas by the Mongol army in 1241 is noted at
the Battle of Legnica (in Silesia, southern Europe). Weapons delivery systems were also
described in artillery manuals of the ancient Chinese military. During the Jurchen siege of
Xiangyang from 1206 to 1207, defenders of the Song dynasty prepared baked mud balls
filled with noxious substances to be launched9by catapults (Figure 2.1; Meng, 2005). The
rationale for this design was twofold: the first was to release a spray of poisoned shrapnel
on impact so as to inflict widespread damage, and the second was to deny the attacking
Jurchens the opportunity to reuse the weapons by throwing them back over the city walls.
The first pharaoh, Menes, cultivated, studied, and collected poisons from plants,
animals, and minerals in 3000 b.c.e. Egyptians also studied the lethal effects of
hydrocyanic acid (Osius, 1957). During the First Sacred War in 590 b.c.e., Athens and
Sicyon plotted to lay siege to the city of Kirrha in retaliation for the harassment of
pilgrims to the Oracle of Apollo at Delphi. Solon, the sage of Athens, had the main water
supply to Kirrha poisoned with hellebore roots, causing diarrhea that led to the defeat of
the besieged city (Hilmas et al., 2008). In 423 b.c.e., during the Peloponnesian War
between Athens and Sparta, Spartan forces besieging an Athenian walled fort ignited a
mixture of wood, tar, and sulfur and directed the smoke through a hollowed-out beam
into the fort. The intent was for the noxious smoke to incapacitate the Athenians, thus
rendering them susceptible to the Spartan assault that followed (the Spartans eventually
took the fort). Also during that war, sulfur-containing substances were ignited and the
gases were carried by the wind onto the besieged Spartan city of Sphacteria by
Demosthenes. During the assault on Ambracia in Epirus in 187 b.c.e., the Roman army
used choking smoke and caustic ash as a siege weapon.
The Romans are also known to have practiced chemical warfare against enemy’s
crops. One famous, although still-debated, event followed the defeat of Carthage in the
Third Punic War (146 b.c.e.), where all farm fields in and around Carthage were sown
with salt to prevent resettlement. The use of irritating or caustic compounds is
documented in numerous ancient military writings. Sand was heated to the point of being
red-hot and hurled at the enemy (it often penetrated chinks in armor). Quicklime (calcium
oxide) was found to be an effective lachrymatory (tear generating) material and skin
irritant, and is described by Quintus Curtius in the first century c.e. (Partington, 1960).
Later, during the thirteenth century, pots filled with lime and caustic potash were hung
from the rigging of ships to be thrown into the eyes of the enemy. The Greek weapon
Kovía (dust) included quicklime and incense that had been distilled from resinous wood
(Partington, 1960). Some of the ancients associated Kovía with sulfides of arsenic.
Probably the most common use of chemicals in war during ancient times was via flame
weapons. A primitive flamethrower was used as early as the fifth century b.c.e. By the
fourth century b.c.e., a number of recipes existed for producing incendiary compositions,
such as that provided by Aineias in his On the Defense of Fortified Positions, where a
mixture of pitch, sulfur, granulated frankincense, and pine sawdust in packages were set
aflame (Langford, 2004). One benefit of the mixture, according to Aineias, is the
difficulty of extinguishing it. The sulfur would also produce toxic fumes. According to
historical documents, a major interest in the use of additives in flaming mixtures was
related to their value in producing a hotter flame; for example, salt had been added
because it was thought to produce a hotter flame, rather than for the production of an
irritating smoke.
The most famous incendiary composition of the ancients was the so-called Greek
fire of the Byzantine Empire. This secret weapon of the Eastern Roman Emperors is said
to have been invented by a Syrian engineer in 673 c.e. This mysterious material had the
amazing property of burning on contact with water. The liquid fire was hurled onto
enemy ships from spray devices and burst into flames on contact. As the mixture was
reputed to be inextinguishable and burned even on water, it caused panic and dread
among enemies. Using Greek fire against enemy ships, the Byzantines were able to rout
the Arab fleet at the battle of Kyzikos in 678 c.e. During the Renaissance, developments
in chemical warfare continued, even with Leonardo da Vinci as a proponent of the
technology.
It is unknown whether this powder was actually used in warfare. Da Vinci was
also one of the early designers of chemically protective clothing. His notes include a
description of a protective mask that shields the eyes, nose, and mouth of the user from
dust and smoke. This mask was found to be a more effective protection against his toxic
powders than a damp cloth, which had originally been proposed (CBWinfo.com, 2005a).
Warring armies enhanced their capabilities by filling incendiary shells, termed carcasses
or stinkpots, with noxious substances and firing them at enemy lines. Contents included
sulfur, tallow, rosin, turpentine, saltpeter, and antimony. The primary function of these
projectiles was to start fires; however, it was observed that hurling carcasses could at
least distract the enemy as a result of the fumes. A variety of fills were developed to
maximize the effects of the smoke. Gunners of the Imperial Artillery were reputed to
have extensively used toxic fills during the Thirty Years’ War. The experience with
noxious smokes would lead to further experimentation in the ensuing years. During his
siege of the city of Groningen in 1672, the Bishop of Munster, Christoph Bernhard van
Galen, gained the nickname Bommen Berend (or Bombing Berend) because of his
extensive use of artillery. He used various explosive and incendiary devices packed with
belladonna, intended to produce toxic fumes. These weapons did not alter the course of
the battle, however, in part because wind direction was not considered.
During the U.S. Civil War, a New York schoolteacher proposed the use of
chlorine gas as an offensive weapon against Confederate forces, delivered by filling
artillery shells with 2 to 3 quarts of liquid chlorine, which could release giant clouds of
toxic chlorine gas. Apparently, his plan was never seriously considered. In 1874, the
Brussels Convention on the Law and Customs of War was adopted. The Convention
prohibited the use of poison or poisoned weapons and the use of arms or material to cause
unnecessary suffering. In 1899, an international peace conference held in The Hague led
to the signing of an agreement that prohibited the use of projectiles filled with
asphyxiating or poison gas. The proposal was passed, with a single dissenting vote from
the United States. The Americans argued that “the inventiveness of Americans should not
be restricted in the development of new weapons.”
World War I became known as the chemists’ war, for the deadly gases it
introduced to combat (Jacobs, 2013). It is commonly believed that the German army was
the first nation to use poison gas during World War I; however, gas was initially
deployed by the French. In August 1914, the first month of the war, the French fired 26-
mm tear gas grenades containing xylyl bromide against the Germans. The grenades were
considered to be of little military worth; regardless, however, the French continued to
consider the use of lachrymating (i.e., causing the eyes to tear) agents against the
Germans (Smart, 1997). Newspapers reported that France had developed a liquid
explosive, turpinite, which released toxic fumes. After a French bombardment had
asphyxiated soldiers, Germany blamed the deaths on turpinite. The German troops later
uncovered a French document describing chloroacetone cartridges and grenades, and
instructions regarding their use. This evidence convinced the German High Command
that Germany was justified in using poison gas.
Fritz Haber of the Kaiser Wilhelm Institute of Physics is credited with the idea of
releasing toxic gas late in 1914. Due to shortages of artillery shells, Haber reasoned that a
chemical gas cloud could overcome the enemy’s trenches and earthworks (Figure 2.2).
Furthermore, gas released from storage cylinders would cover a much broader area than
would gas dispersed from artillery shells. Haber suggested chlorine as a weapon because
it was abundant in German industries (Smart, 1997). Chlorine gas was released on
battlefields near Ypres, Belgium, on April 22, 1915. Immediately upon inhalation, it
brought on choking attacks and severe damage to victims’ respiratory tracts, skin, and
mucous membranes. The Germans’ use of chlorine triggered immediate widespread
condemnation, and Germany was criticized for abrogating The Hague Conventions of
1899. Germany justified its actions by stating that The Hague Conventions addressed
only projectiles that diffused asphyxiating or hazardous gases, and did not address gases
released by cylinders (Figure 2.3). The Germans added that France broke the poison gas
conventions first.
The British Army went on to use poison gas with enthusiasm and mounted more
gas attacks than any other adversary. At this point in the war, delivery methods for
chemical agents were either by cylinder emplacements or artillery shells. Delivery by
cylinders was common initially because they were refillable and, in the case of Germany,
large-scale gas shell production capabilities were lacking. Once artillery shells were
developed that could be filled with chemical agents, properly sealed, and follow a steady
flight path, the Germans stopped using cylinder-based attacks and relied solely on
artillery shells. Chlorine was not terribly efficient as a weapon; it produced a distinct
greenish cloud and an obvious odor, making it easy to detect. Enemy soldiers in the
trenches might have sufficient warning of its arrival, and thus time to don protective gear.
Chlorine was watersoluble, so the simple act of soaking a cotton cloth with water or a
solution of bicarbonate of soda (urine was also recommended) and covering the face was
sufficient to protect many soldiers. A more discrete weapon was therefore needed on the
battlefield.
Germany introduced sulfur mustards (commonly known as mustard gas) against
the Russians at Riga in September 1917. It was used by the Germans against Canadian
soldiers in 1917 and later against the French. At that time, mustard gas was termed
Yperite, which is derived from its use near the Belgian city of Ypres. Delivered in
artillery shells, mustard gas was dispersed as an aerosol mixed with other chemicals,
giving it a characteristic yellow-brown color and distinctive odor. The gas caused severe
blisters both internally and externally, usually hours after being exposed (Figure 2.5). The
British eventually developed a mustard gas weapon, first using it in September 1918
during the breaking of the Hindenburg Line. Personal protection against mustard gas was
less effective than against either chlorine or phosgene gas. A simple gas mask did not
protect against skin absorption. In only a very small percentage of cases was mustard gas
lethal to troops. Its primary military use was as an incapacitating agent. The gas was later
used as a so-called area denial weapon, that is, it was disseminated over a village or
airstrip to prevent access by the enemy.
By 1918 the use of poison gas had become widespread, particularly on the
Western Front. If the war had continued into 1919 both sides had planned on inserting
poison gases into 30%–50% of all manufactured shells (Firstworldwar.com, 2007). Other
types of gases produced for the war included bromine and chloropicrin. The French army
occasionally made use of a nerve gas obtained from prussic acid. However, the most
widely used gases continued to be chlorine, phosgene, and mustard gas
(FirstWorldwar.com, 2007). Of all chemical warfare agents used, chlorine, phosgene,
diphosgene, chloropicrin, hydrogen cyanide, cyanogen chloride, and mustard were
produced and used in largest quantities. As the war continued, many other toxins were
tested for utility as chemical warfare agents.
During World War I, approximately 190,000 tons of toxic chemicals including
chlorine, phosgene, and mustard gas were deployed against both soldiers and civilians,
resulting in more than 100,000 deaths and more than 1 million casualties. The German
army was the heaviest user of gas during the war. Historians estimate that German use
reached 68,000 tons; the French used 36,000 tons; and the British 25,000. By 1918,
combatants had become much better prepared to respond to gas attacks. Filter respirators
(using charcoal or antidote chemicals) were available and proved effective; however, use
of such gear in trenches was cumbersome. Fritz Haber (Figure 2.6), a German chemist
and zealous proponent of chemical weaponry, likened chemical warfare to an intellectual
challenge, telling industrialist Carl9Duisberg that9 “gas weapons and gas defense turn
warfare into a chess match”.
Regardless, however, poison gas did not prove itself as the weapon to turn the tide
of the war. With the Armistice, the horrors of chemical warfare prompted the banning of
chemical weapons in war. This commitment resulted in the signing, by 16 nations, of the
1925 Geneva Protocol for the Prohibition of the Use of Asphyxiating, Poisonous or Other
Gases, and Bacteriological Methods of Warfare. The United States did not sign the
Protocol until 1975. The Geneva Protocol does not, incidentally, prohibit the
development, production, or possession of chemical weapons, only its use on the
battlefield. Many nations signing the Geneva Protocol included the caveat that they had
the right to retaliate with chemical weapons should they be attacked in such a way.
After World War I, a number of isolated incidents were documented in which
mustard gas was used against both military personnel and civilian populations. During
this period, the United States and many European nations attempted to establish new
colonial possessions; in other cases, they were faced with holding on to increasingly
restless colonies. During the interwar period, chemical agents were sometimes used to
repress populations and quash rebellions. In 1920, the Arab and Kurdish populations of
Mesopotamia revolted against British occupation. With time and with rising British
casualties, the British resorted to increasingly repressive measures. Colonial Secretary
Winston Churchill argued for the use of mustard gas on the Mesopotamian resistors.
Churchill believed that chemical weapons could be inexpensively used against the
Mesopotamian tribes.
Chemical agents were not used by either the Allies or Axis Powers during World
War II. Hitler is known to have been a victim of a sulfur mustard attack during World
War I and was therefore opposed to its use by Germany. In addition, Germany decided
not to use the newly discovered nerve agents, fearing a devastating Allied retaliation with
those same highly toxic agents. Civilians and prisoners of both the Germans and Japanese
were victims of chemical weapons during the war. Mustard gas was intentionally used in
so-called medical experiments on prisoners, presumably to obtain data on its effects and
possible treatment. The Germans conducted experiments at both the Sachsenhausen and
Natzweiler concentration camps to investigate mustard gas injuries. The Japanese
subjected Chinese prisoners and civilians to experiments with sulfur mustards as well.
The Allies also carried out experiments with mustard gas, but on volunteers. The Allied
experiments were not conducted to the point of death of the experimental subjects, as had
occurred in the German and Japanese experiments. The Allied experiments were also
better designed and led to improvements in protective gear and treatment methods.
After World War II, several countries were accused of or documented using
chemical weapons. Between 1963 and 1967, the United Arab Republic (Egypt)
intervened in the Yemeni Civil War, aiding the armies fighting royalist forces. Egypt was
accused of using sulfur mustard during the conflict. Other chemicals such as phosgene
were also reported to have been used. Iraq began conducting research in chemical
weapons development and deployment in the 1970s. Iraq used mustard gas during its war
with Iran (1982–1988), with the first confirmed use in August 1983 near Haj Umran.
Over the following months, both the physical and psychological effects of mustard on the
Iranians were obvious; several thousand fatalities due to mustard were claimed; however,
the exact numbers are under debate. In an attempt to establish whether chemical warfare
agents had been used during the war, three United Nations (UN) missions (in 1984, 1986,
and 1987) conducted field inspections, clinical examination of casualties, and laboratory
analyses of chemical ammunition.
The countries participating in BWC negotiations further committed themselves to
negotiate a treaty to ban the use and production of chemical weapons. In 1980, an ad hoc
working group on chemical weapons was established at the Committee on Disarmament.
This group received a formal mandate to negotiate the text of a Convention banning
chemical weapons. The treaty was designed to include a verification protocol to ensure
the compliance by nations with the treaty’s provisions. Negotiations on a chemical
weapons treaty continued from 1980 to 1992. The text of the treaty was adopted by the
Conference on Disarmament in Geneva on September 3, 1992, and became known as the
Convention on the Prohibition of Development, Production, Stockpiling, and Use of
Chemical Weapons and on Their Destruction (Chemical Weapons Convention [CWC]).
The CWC was the first disarmament agreement negotiated with the ultimate goal of the
elimination of an entire category of weapons of mass destruction under international
control.
In 1995, Aum Shinrikyo, a religious sect based in Japan, released sarin in the
Tokyo Metro system, killing 11. The attack was directed against trains passing through
Kasumigaseki and Nagatacho, home to the Japanese government. Approximately 6000
persons were exposed. A total of 3227 went to the hospital (see Box 2.3). In 2005,
Scotland Yard claimed to have thwarted an al-Qaeda sarin gas attack on the British
Parliament. The plot to release nerve gas on the House of Commons was devised the
previous year and uncovered through decoded e-mails on computers seized from terror
suspects in Britain and Pakistan. Police and the secret service identified a six-person al-
Qaeda cell that carried out extensive research and videotaped reconnaissance missions in
preparation for the attack.
B. Chemical Weapons Types
Nerve agents (also known as nerve gases, although these chemicals are liquid at
room temperature) comprise a class of phosphorus-containing organic chemicals that
inhibit the acetylcholinesterase enzyme in mammals and which are used both as
insecticides and weapons (Table 2.1). These extremely toxic agents are classified as G-
series or V-series. The G-agents (named for the German scientists who discovered them)
tend to volatilize and dissipate relatively quickly; therefore, G-agents are considered to be
nonpersistent chemical weapons. In contrast, all V-agents are persistent, that is, they do
not readily degrade biologically or chemically, nor do they readily volatilize.
In 1935, the Nazi government passed a decree that required all inventions of
possible military significance to be reported to the Ministry of War, so in May 1937
Schrader provided a sample of tabun to the Army Weapons Office in Berlin and gave a
demonstration, after which all of Schrader’s nerve agent research became classified. A
facility for largescale manufacture of tabun began production in 1942. About 12,500 tons
were manufactured before the plant was overrun by advancing Soviet forces. Large
volumes of the agent were dumped into the sea. Much of our basic knowledge about the
clinical effects of nerve agents is the result of research performed in the decades after
World War II. Poisoning by a nerve agent leads to miosis, profuse salivation,
convulsions, involuntary urination and defecation, and eventual death by asphyxiation
due to loss of control over respiratory muscles. Nerve agents can be absorbed through the
skin; therefore, those individuals likely to be exposed to such agents must wear a Level A
suit in addition to a supplied air respirator (e.g., self-contained breathing apparatus, or in-
line respirator).
Tabun (military abbreviation: GA) is an extremely toxic nerve agent that is a clear
to brown, tasteless liquid with a faint fruity odor. Tabun is a member of a class of
phosphoruscontaining organic chemicals (organophosphates) and is classified as a
weapon of mass destruction by the UN; its production is strictly monitored, and
stockpiling is prohibited by the CWC of 1993. Tabun, along with GB (sarin), GD
(soman), and GF (cyclosarin) comprise the so-called G-series nerve agents. Tabun is
volatile and evaporates readily at ambient temperatures; it is, however, less volatile than
sarin or soman. Tabun is much easier to produce than the other G-series weapons, and the
procedures are rather widely understood; because of these factors, countries that are
developing nerve agent capability but which lack advanced industrial technology often
start by producing GA. During the Iran–Iraq War, Iraq used large quantities of chemical
weapons against Iran’s ground forces. Although the most commonly used agents were
mustard gas and sarin, tabun and cyclosarin were also used.
Sarin is a colorless, odorless liquid at room temperature. The compound has a
structure and mechanism of action similar to that of tabun and some commonly used
insecticides. The chemical structure of sarin is shown in Figure 2.10. Sarin, along with
the other G-series and V-series agents, is classified as a weapon of mass destruction by
the UN; stockpiling is prohibited by the CWC of 1993. Sarin was discovered by Gerhard
Schrader and his associates in 1938; it was code-named T-144 and Trilon-46. It is the
most toxic of the so-called G-agents created by German scientists and more than 10 times
as potent as tabun. At room temperature, the low vapor pressure of sarin (2.9 mm Hg at
25°C) makes it relatively ineffective as a weapon to be inhaled. It is made more persistent
by the addition of certain petroleum products.
The V-series of nerve agents (where V stands for venomous) is another class of
phosphoruscontaining organic chemicals that inhibit the acetyl cholinesterase enzyme in
mammals, essentially inhibiting nerve function and/or causing paralysis and ultimately
death. The structure and mode of action of the V-agents are similar to those of the
organophosphate insecticides; like the G-series agents, several of the V-agents were
derived from early insecticide formulations. The V-series of nerve agents includes VE,
VG, VM, and VX. All the V-agents are persistent, that is, they do not readily degrade via
biological or chemical means, nor do they readily volatilize (see Figure 2.8). These
agents are therefore considered more hazardous than the G-series agents such as GB
(sarin) and GA (tabun), which dissipate quickly and incur only short-term effects.
The V-series nerve agents were originally studied by Dr. Ranajit Ghosh, a chemist
at the British firm Imperial Chemical Industries (Croddy and Wirtz, 2005). Dr. Ghosh
determined that the V-agents were extremely effective insecticides; however, they were
considered too toxic for conventional use. In 1952, the British military took a strong
interest in the new formulation and studied it in Porton Down, U.K. Several newly
formulated and chemically similar compounds became the V class of nerve agents. VX
was not considered the U.K.’s optimal chemical agent, however; sarin was the weapon of
choice. In 1956, the United Kingdom unilaterally renounced the use of both chemical and
biological weapons, and in 1958 the British government traded their research on VX
technology with the United States in exchange for information on nuclear weapons. By
1961, the United States went into large-scale production and weaponizing of VX, placing
it in rockets, howitzer shells, and landmines.
VX breaks down slowly in the body; therefore, repeated exposures to VX or other
nerve agents impart a cumulative effect. Symptoms appear within seconds after exposure
to the vapor and from minutes to hours after exposure to the liquid. The effects are often
fatal. It is possible that any VX liquid on the skin, unless washed off immediately, will be
lethal (U.S. CDC, 2006a). Full body protection, including the use of securely fitting
respirator masks, is essential to avoid exposure in the event of a VX release. In the event
of VX exposure, primary consideration should be given to removal of the liquid agent
from the skin before removal of the individual to an uncontaminated area. After removal
from the contaminated location, the victim must be decontaminated by washing the
affected areas with dilute household bleach and flushing with extensive clean water.
After decontamination, clothing is removed and skin contamination washed away. If
possible, decontamination should be completed before the victim is provided with
extensive medical treatment.
Before the CWC of 1997, chemical agent disposal practices included the U.S.
Army’s CHASE (Cut Holes And Sink ’Em) program, initiated in 1964, in which old
ships were loaded with chemical weapons stockpiles and then sunk. CHASE 8 was
conducted on June 15, 1967, in which the S.S. Cpl. Eric G. Gibson was filled with 7380
VX rockets and scuttled in 7200 ft of water off the coast of Atlantic City, New Jersey
(DailyPress.com, 2005). The long-term environmental impacts of exposing VX to
seawater and marine life are unknown. Since 1990, workers and robots at plants in six
states and at Johnston Atoll in the South Pacific have systematically destroyed millions of
pounds of liquid VX, as well as sarin and mustard agent in a variety of containers and
weapons. The remaining American VX stockpile will be eliminated in two facilities in
Kentucky and Colorado (Gustafson, 2013). The VX is hydrolyzed to less toxic by-
products using concentrated caustic solution and rendered nontoxic. In other locations
such as at Johnston Atoll, VX stockpiles were destroyed by high-temperature
incineration.
The typical mechanism of agent toxicity is a reaction with linings of the lungs,
causing perforations where water leaks into the air sacs. The result is delayed pulmonary
edema (fluid buildup in the lungs). Severe adverse effects may not become apparent until
many hours after exposure. If pulmonary edema occurs within about 4 h of exposure, the
victim will likely die despite all medical efforts. Medical management includes admission
to the hospital with bed rest, administration of supplemental oxygen, and intubation (i.e.,
insertion of a tube into an orifice of the body).
Chlorine gas can be pressurized and cooled to convert it to liquid form to facilitate
shipping and storage. When liquid chlorine is released, it converts quickly to a gas that
remains close to the ground (vapor density = 2.5; air = 1.0) and spreads rapidly. The
degree of poisoning caused by chlorine depends on the location of exposure, the quantity
a victim is exposed to, and the duration of exposure. Chlorine gas is highly corrosive
when it contacts moist tissues such as the eyes, skin, and upper respiratory tract; acids are
produced that inflame and damage tissues. Chlorine is highly water-soluble; on contact
with H2O, it forms hypochlorous acid (HClO) and hydrochloric acid (HCl); the unstable
HClO readily decomposes, forming free radicals. As a consequence of these reactions,
water greatly enhances the oxidizing and corrosive effects of chlorine.
Chloropicrin was initially synthesized in 1848 by John Stenhouse, a Scottish
chemist. It was first used as a chemical weapon by Russia during World War I and was
eventually delivered in artillery shells and cylinders by both sides. During the war,
chloropicrin was often released in combination with other agents because chloropicrin
often broke through gas mask filters, making soldiers vulnerable to other gases. After
World War I the importance of chloropicrin as a weapon declined. Due to its strong odor
and having only onefourth the toxicity of phosgene, chloropicrin did not receive the same
attention as other, more potent chemical weapons agents..
Sulfur mustards are a class of cytotoxic vesicant chemical warfare agents that
form large, painful, liquid-filled blisters on exposed skin. At room temperature, most
sulfur mustards are colorless, odorless, and viscous liquids. Some are yellow-brown in
color and have an odor resembling mustard, garlic, or horseradish (hence the name of this
weapon). Sulfur mustard vapor is heavier than air (vapor density = 5.5; air = 1), so it will
settle in low-lying areas. Sulfur mustard has been in existence for almost two centuries; it
is believed to have been first synthesized by Depretz in 1822, by Richie in 1854, and
again in 1859 by Guthrie, who reported in the Quarterly Journal of the Chemical Society
that blisters formed if the liquid was allowed to contact the skin. These early synthesis
reactions resulted in the discovery of related vesicant compounds. By 1886, synthesis
reactions allowed for the production of high yields of relatively pure sulfur mustard.
The effects of sulfur mustard attacks on the Allies were devastating; in the first
week of German use of the agent, the British suffered more than 2900 casualties. Before
the use of mustard gas, medical units had treated about 350 gas casualties per week. In
the first 39weeks of German use of mustard gas, the British reported 14,296 gas casualties
(CBWinfo .com, 2005b). Sulfur mustard soon became a prominent battlefield weapon. It
became the primary chemical agent used by the Germans, as they discovered both its
physical as well as its psychological effects. PPE was very crude and in short supply
during the Great War. Some troops were equipped with oilcloth uniforms that could
provide limited protection. Many troops had to settle for simple protection such as a
mixture of zinc stearate and vegetable oil that was rubbed over the body. This lotion
would have to be removed as soon as possible after an attack, as it would absorb mustard
gas and eventually allow it to reach the skin.
In addition to its vesicant properties, sulfur mustard is also carcinogenic and
mutagenic. Several mechanisms are suggested for the damage caused by mustard agents;
one involves the bonding of the sulfur mustard molecule to the bases in DNA. The
bonding may result in breakages of DNA strands followed by the formation of new
bridges between the strands. Such bridges prevent DNA from functioning normally
during cell division and may lead to cell death. Damage to DNA may also cause
mutations and disturb natural DNA repair mechanisms. Such damage to DNA may be
responsible for the increased frequency of cancer observed after exposure to sulfur
mustard.
Although no antidote exists for sulfur mustard, exposure is usually not fatal (U.S.
CDC, 2006b). There is no treatment or antidote that can ameliorate injury from mustard
agent. Instead, efforts are made to treat the symptoms. The most important measure is to
rapidly and thoroughly decontaminate the patient and thereby prevent further exposure.
Clothing must be removed, and the skin decontaminated with a suitable solution and
washed with soap and water. If the hair is contaminated it must be shaved off. Eyes are
rinsed with water or a physiological salt solution for at least 5 min (OPCW, n.d.). It is
essential to control infections using antibiotics. Pain can be eased by administration of
local anesthetics. After skin injuries have healed, it may be necessary to apply plastic
surgery. Lung injuries are treated with bronchodilatory treatment. Medicine to relieve
coughing and also cortisone preparations may be used. Eye injuries are treated locally
with painkillers and with antibiotics if required.
Lewisite is named after the U.S. chemist Winford Lewis (1878–1943), who in
1918 discovered a graduate thesis describing its synthesis and went on to formulate a
battlefield weapon. The methods in the original thesis called for the reaction of arsenic
trichloride with acetylene in the presence of mercuric chloride in HCl. German scientists
are believed to have studied this compound earlier (Buscher and Conway, 1944; Prentiss,
1937). After World War I, the U.S. military became interested in lewisite; however, field
trials during World War II demonstrated that casualty effects were not consistent under
high humidity due to its high rate of hydrolysis. In addition, its distinct odor and ability to
cause lachrymation induced troops to don protective gear and avoid contaminated areas.
The United States produced about 20,000 tons of lewisite. It was replaced by sulfur
mustard and ultimately declared obsolete by the 1950s. Stockpiles of lewisite were
neutralized by oxidation with chlorine and disposed into the Gulf of Mexico.
C. Definition of Explosives
In modern societies, the risk of explosive incidents is significant. Beyond military
applications, numerous businesses manufacture, transport, and use low and high
explosives in daily operations (i.e., mining and demolition). In addition, explosives
continue to be the weapon of choice for terrorists worldwide—of all the weapons of mass
destruction (WMDs) (chemical, biological, radiological, nuclear, explosive) reportedly
used, the most commonly used, by far, are explosive devices. Emergency responders
encounter explosives in a variety of applications. Military and commercial explosives
may be adapted for improvised bombs. In addition, many powerful explosives can be
home-made from simple ingredients. The hazards of explosive weapons are underscored
by their relative ease of manufacture; information on bomb making is available in library
books and in bomb training manuals available at many gun shows. In addition, detailed
bomb-making instructions are available on the Internet.
An explosive device is any device designed to explode, with concomitant release
of a blast wave, gases, light, heat, and sound. A nuclear detonation occurs within the
nucleus of an atom as a result of either fission or fusion processes (see Chapter 5).
Fission occurs when the nucleus of an atom is split, resulting in the release of massive
quantities of energy. Nuclear fusion occurs when light nuclei (e.g., hydrogen or
deuterium atoms) are fused, forming a heavier element with the generation of substantial
energy. Both reactions have been intensively studied and adapted for use in nuclear
weapons. Fission devices were dropped on Hiroshima and Nagasaki, Japan, in 1945.
Fusion devices have never been used in warfare. In a mechanical explosion, the internal
pressure of a vessel is greater than its ability to withstand the pressure. An example is the
bursting of a boiler. A chemical explosion results from the ignition of an energetic
(reactive) substance. A chemical disintegration occurs, along with the production of light,
heat, and shock wave.
While chemical reactions do indeed involve changes in the electron configuration
of atoms and molecules, explosions typically occur as a result of rapid and violent
chemical reactions that release large amounts of energy in a short period of time. These
reactions can take place within the electron cloud of an element, but the explosion itself is
not directly caused by changes in the electron configuration. Explosions are often the
result of exothermic reactions, where chemical bonds are broken and new bonds are
formed, releasing energy in the form of heat, light, and pressure. This sudden release of
energy generates a shockwave that propagates outward from the site of the explosion,
causing damage to surrounding materials and structures. In some cases, explosions may
involve combustion reactions, where a fuel (such as gasoline or gunpowder) reacts with
an oxidizer (such as oxygen) to produce heat, light, and gases such as carbon dioxide and
water vapor. The rapid expansion of these gases creates a sudden increase in pressure,
resulting in an explosive release of energy.
Other types of explosions may involve the rapid decomposition of unstable
compounds or the detonation of high-energy materials such as explosives or propellants.
In these cases, the release of energy is often triggered by an external stimulus such as
heat, shock, or friction, initiating a chain reaction that leads to a rapid and violent
expansion of gases. While chemical reactions do occur within the electron cloud of an
element, it is the rapid release of energy during certain types of reactions that leads to
explosions. Understanding the underlying chemical processes involved in explosions is
crucial for developing safety measures and mitigating the risks associated with hazardous
materials and environments.
D. History of Explosives Development
Among the first of all energetic (explosive) materials ever developed and tested
was black powder. Historians, however, still differ regarding its origins; the Chinese,
Hindus, and Arabs have all been credited with its discovery. In 1200 c.e., Arabian Abd
Allah recorded the use of saltpeter as a key ingredient of black powder. In 1249, Roger
Bacon, an English monk, documented a formula for black powder that included saltpeter,
charcoal, and sulfur. Early in its development, black powder was found to be useful for
both military and work purposes. The Chinese and Europeans became aware of the
benefits of black powder at about the same time. By 1232, the Chinese developed rockets
and a weapon they called heaven-shaking thunder crash bomb, an iron bomb attached to a
chain that could be lowered from city walls to explode among attacking forces (Langford,
2004; Meng, 2005). The earliest mention of black powder on military supply lists was in
1326.
By the nineteenth century, modern energetic materials technology had arrived.
New explosives were discovered, replacing the black powder mixtures that had been so
popular for centuries for weapons and blasting. New energetic materials influenced the
design and performance of weapons; concomitantly, the invention of new weapons
prompted the search for more effective and less expensive explosives. In 1800, Edward
Howard, an English chemist, discovered mercury fulminate, a highly sensitive and
powerful explosive. In 1807, the use of mercury fulminate as an explosive primer was
patented by the Scot Alexander Forsyth. In 1825, Rev. Dr. Clayton in England isolated
benzene, creosote, and naphthalene from coal tar. These products were later incorporated
into explosives such as trinitrobenzene and nitronaphthalene. The application of a flame
directly to explosive solids (e.g., in mining) was a highly dangerous activity. In 1831, the
safety fuse was invented by British engineer William Bickford. The so-called Bickford
fuse contained a core of black powder tightly wrapped in jute yarn. The fuse was
designed to ensure accurate and consistent burning time. The Bickford safety fuse was
later made waterproof by applying a coat of asphalt covered with textile.
Nitrostarch was discovered in 1833 by Henri Braconnot, a French chemist, while
dissolving starch in concentrated nitric acid (Labrude and Becq, 2003). In 1845,
guncotton (later termed nitrocellulose) was formulated by Christian Schoenbein, a
German chemist at the University of Basel, Switzerland, by treating cotton with a nitric
acid–sulfuric acid mixture. Schoenbein demonstrated that nitrocellulose was up to four
times as powerful as black powder for blasting. During early efforts to manufacture
guncotton, serious accidental explosions occurred, which delayed its general use as an
explosive. Eventually, however, guncotton became universally accepted for use in
blasting. Nitroglycerin, an ester of glycerin and nitric acid, was invented by Asconio
Sobrero, an Italian chemist, in 1846. Nitroglycerin was found to be extremely sensitive to
even slight shocks, so its commercial use was delayed. This promising explosive was
eventually used on a large scale with the invention of dynamite, blasting gelatin, and
smokeless powder. Nitroglycerin production facilities were designed for commercial
application by Alfred Nobel, a Swedish chemist (Figure 6.1). In 1862, the first plant was
constructed at Heleneborg, Sweden.
In 1863, trinitrotoluene (TNT) was prepared by J. Willibrand, a German scientist.
TNT had been used for many years in the dye industry; however, it was not used as an
explosive until 1904. Thereafter, TNT became one of the most commonly used high
explosives. Two years later, nitrocellulose was purified by Sir Frederick Abel, an English
chemist. Abel pulped, washed, and compressed nitrocellulose into blocks, sheets, disks,
and cylinders. These forms were found to be useful for rock blasting. In 1866, dynamite
was invented by Alfred Nobel by absorbing nitroglycerin (75%) in kieselguhr
(diatomaceous earth) (25%). Kieselguhr, an inactive ingredient, stabilized the
nitroglycerin and made dynamite a much safer explosive to handle. Dynamites with an
active base were soon patented by Nobel. In these new formulations, nitroglycerin was
mixed with combustibles (sawdust, charcoal, starch, etc.), and oxidizers (sodium nitrate
or potassium nitrate). By 1884, ammonium nitrate became widely used in dynamite
formulations. These additives resulted in a more efficient explosive than earlier dynamite
recipes. In 1868, Nobel went on to invent the blasting cap, a device used to initiate larger
explosives. Nobel’s cap consisted of mercury fulminate in a copper tube. The cap was
crimped to one end of a safety fuse and then inserted into the dynamite casing.
In the early twentieth century, antifreeze for dynamite was researched extensively
in many countries, in part as a result of a disastrous explosion during defrosting dynamite
in Germany. Sigurd Nauckhoff of Sweden published his work on dynamite antifreeze in
1905, listing requirements for a satisfactory formulation (Fordham, 1980). In the same
year, nitrostarch was produced in a stable form. Nitrostarch is similar to nitrocellulose but
is lower in strength. Nitrostarch does not cause negative health effects from skin contact
as do TNT, nitroglycerin, and dynamite. Early in the new century, substantial strides
were made in development of detonating cord and blasting caps. In 1908, a detonating
cord containing TNT instead of black powder was patented in France. This cord had a
detonation velocity of 48809 m/s (or 16,0009ft/s). In 1914, lead styphnate
(trinitroresorcinol), an initiating explosive, was first prepared by E.9von Herz of
Germany. Russian Col. A. Solonina was the first to propose using lead styphnate in
detonators. Ammonium picrate (Dunnite or Explosive D) was standardized in the United
States as a bursting charge for armor-piercing shells. These projectiles could be fired
through 12 in of armor plate, and could be detonated by an insensitive primer.
At the outbreak of war in the summer of 1914, the German General Staff had
planned to fight a conflict fueled predominantly by high explosives. The Germans rapidly
converted their chemical industrial facilities to production of synthetic ammonia, nitric
acid, and sulfuric acid, all required for the manufacture of explosives and chemical
warfare agents. The key to German explosives production was the Haber process for
producing ammonia from atmospheric nitrogen. Using the Haber process, Germany
became independent of foreign nations for its supply of ammonia and nitric acid. Smoke
munitions were used on land and sea by the belligerent powers in World War I. In July
1915, the British used smoke pots, vessels filled with pitch, tallow, black powder, and
potassium nitrate. The first large-scale smoke operation occurred on September 20, 1915,
when the Canadians fired several thousand smoke shells from trench mortars during the
attack against Messines Ridge (Belgium) in mid-1917.
During the period between the two world wars, the U.S. Army invested
significant funding and resources toward the development of ammunition and weaponry.
During these two decades RDX, PETN, ethylenedinitramine (EDNA), lead styphnate,
and lead azide were formulated as military explosives. The development of processes for
producing toluene from petroleum greatly enhanced the availability of TNT, and
permitted the manufacture of powerful and castable explosives such as composition B
and pentolite (U.S. Department of the Army, 1990). During World War I, the supply of
toluene was quite limited—it was derived primarily from coal as a by-product of coke
ovens, and some was extracted from natural gas.
When World War II began in September 1939, the standard United States charge
for highexplosive bombs was TNT. Early in the war, however, other fillings were used,
such as RDX, an explosive known for its great power and brisance but generally
considered too sensitive. The British developed a method of using beeswax to desensitize
the RDX, and used this explosive with success in the 2-ton blockbuster bombs dropped
on Berlin in April 1941. The most sensitive of all high explosives was PETN, which was
even more readily detonated than RDX. PETN was therefore, diluted with TNT to
desensitize it. The new composition, named pentolite, has been extensively used in
detonators, bazooka rockets, rifle grenades, boosting devices, and in the shaped charges
of antitank shells.
The development of napalm (nap for naphthenic acids; palm for the coconut fatty
acids that comprised the thickener) by the United States in 1941 made use of gasoline in
flame weapons. This gelled mixture made it possible for aircraft to deliver firebombs
over difficult areas. Napalm proved to be one of the most effective aerial incendiary
agents in the war. On the evening of March 9, 1945, more than 300 B-29 bombers flew
over Tokyo, dropping about 2000 tons of incendiaries, mostly clusters of M69 6-lb
bomblets. The M69 was a tube that contained a black powder propellant charge that
ignited and ejected the napalm filling from the tube (U.S. Department of the Army,
1990). Aerial photos indicated 16 mi2 had been destroyed by fire. Records examined
after the war showed that more than 250,000 buildings in Tokyo were destroyed in this
raid. More than 100,000 tons of incendiaries were dropped on the cities of Japan during
World War II. Most were M69 bomb clusters. In 1992, in the aftermath of the Gulf War,
explosives were used to extinguish most of the 700 Kuwaiti oil well fires that had been
set by Saddam Hussein’s retreating troops. One method involved the placement of high
explosives in augered shafts at inclined angles to the well pipe. The explosives removed
soil and rock to create a ramp for access to the well pipe and also to crimp the well pipe.
Two bombs may be physically placed such that they straddle the well.
E. Characteristics and Classification of Explosives
Explosives are classified as low or high explosives based upon rate of
decomposition. Low explosives burn rapidly (or deflagrate), whereas high explosives
detonate (Box 6.1). This classification depends, in part, on how the materials are
packaged and used. One of the most important properties involved in rating an explosive
is detonation velocity, a value designated for both confined and unconfined conditions.
Detonation velocity is the speed at which the detonation wave travels through the
explosive. This property is usually measured in an unconfined column of explosive 1¼
inch (3.2 cm) in diameter. Detonation velocity is a function of chemical composition of
the explosive, density, particle size, charge diameter, and degree of confinement. Factors
that increase detonation velocity include decreased particle size, increased charge (i.e.,
fuel) diameter, and increased confinement. The confined detonation velocity of
commercial explosives varies from about 4000 to 25,000 ft/s.
Propellants are designed to release a gas under controlled conditions to perform
useful work functions. Examples include the deflagration of gunpowder for firing a
projectile (e.g., bullet) out of the barrel of a gun. The key to safe and effective use of
propellants is to maintain a controlled release of gas. When propellants are confined or
when control is lost, explosions may occur. Pyrotechnics are designed to produce light,
smoke, heat, and sound. The pyrotechnics we are most familiar with include fireworks,
which are designed for entertainment. However, pyrotechnics are also important in the
workplace, for example, as ingredients of road flares and other illumination devices.
Whereas propellants or low explosives are designed to produce a controlled
release of energy, high explosives are engineered to detonate with a near-instantaneous
release of energy. High explosives function by detonation; shock and heat waves travel at
speeds greater than 1130 ft/s. Some energetic materials have been measured to attain
speeds of more than 29,000 ft/s. By virtue of their destructive force, high explosives are
used in military ordnance. High explosives are usually initiated by a blasting cap but high
temperatures, shock, or friction may also cause initiation. High explosives are divided
into three classes—primary, secondary, and tertiary— based on their sensitivities to
various stimuli. Primary explosives are the most sensitive and tertiary the least sensitive.
For first responders attempting to identify the safest course of action in a hazardous
situation, understanding sensitivity of an explosive material is critical.
The U.S. military had attempted to use a number of primary explosives for
conventional munitions; however, because of their extreme sensitivity, such use was
abandoned. As a result of their sensitivity, primary explosives are typically used in only
small quantities, for example, in blasting caps (Box 6.2). Primary explosives are therefore
useful in initiating less sensitive, but more powerful secondary explosives in a so-called
firing train. Secondary explosives are markedly less sensitive than primary explosives
and require a significant stimulus (e.g., the energy levels created by another explosion) to
detonate; therefore, secondary explosives are initiated by a primary explosive. Secondary
explosives are most commonly used in bulk quantities.
Tertiary explosives are the most insensitive of high explosives. Most formulations
contain the common salt, ammonium nitrate. Ammonium nitrate fuel oil (ANFO) is a
common tertiary explosive and a very insensitive substance. ANFO is discussed later in
this section. Tertiary explosives require a significant stimulus to cause detonation. A
blasting cap, shock, or small flame will not initiate them. Usually, a quantity of secondary
explosive (a booster), for example, dynamite, is needed for initiation. In military and
commercial explosives as well as in terrorist weapons, a sequence of primary, secondary,
and often tertiary explosives is used for maximum effectiveness. The firing train (also
known as the explosive train) is a specific sequence of steps resulting in progressively
larger explosions. The firing train explosions increase in size until the main charge is
detonated.
A minor stimulus begins the train. The stimulus can be fire, an electric pulse, or
other insult. If the stimulus is a flame, this will ignite a propellant (e.g., black powder
contained within a time fuse). The burning propellant delivers flame to a primary
explosive or detonator contained in a blasting cap. The primary explosive subsequently
detonates, delivering a shock and flame to the secondary explosive. The secondary
explosive or booster subsequently detonates, delivering a significant shock to the tertiary
explosive. The tertiary explosive or main charge then detonates, completing the firing
train. Other possible firing trains, which vary in complexity, can be devised. For example,
for black powder confined within a steel pipe in an IED, only three steps are needed: (1) a
flame ignites a fuse, (2) the fuse ignites the black powder inside the pipe, (3) a DDT, and
an explosion occurs.
F. Commercial and Military Explosives
Military explosives are designed to deliver an enormous quantity of energy very
quickly. This ability also allows them to effectively shatter or cut targets. Many
commercial explosives have the same characteristics as military explosives; however,
numerous commercial explosives are designed to push or heave a target, rather than
shatter. Black powder is composed of 75% potassium nitrate (saltpeter) or sodium nitrate,
10% sulfur, and 15% charcoal, a recipe essentially unchanged since its discovery by
Chinese alchemists in the ninth century. Black powder mixtures range in color from black
to dark brown, and grains range in size from fine powder to large granules (prills). The
burning speed of black powder is controlled by granule size (i.e., surface area)—the
smaller the granules, the more rapid the burn rate.
The burning phenomenon occurs so vigorously that it may resemble an explosion.
Black powder is such a reactive formulation that it should be stored, transported, and
handled as if it were a high explosive. Black powder is indeed classified as a high
explosive under DOT regulations. Packages of granular and compressed black powder
are labeled EXPLOSIVE 1.1D; transport vehicles are placarded EXPLOSIVES 1.1D.
Black powder does not deteriorate with age. Water may temporarily desensitize it;
however, once dry, it regains its original reactive composition. Black powder is
extremely sensitive to friction, flame, impact, shock, and static electricity. This
characteristic makes black powder one of the most dangerous explosives to handle.
Smokeless powder (Figure 6.7) has replaced black powder in many applications. The
term smokeless has been used because its combustion products are mainly gaseous,
compared to more than 50% solid products for black powder.
Nitroglycerin (1,2,3-trinitroxypropane or glycerin trinitrate) is an oily, pale yellow
liquid high explosive (Figure 6.8). For well over a century, nitroglycerin has been a key
ingredient in the manufacture of explosives, specifically dynamite. As early as the 1880s,
nitroglycerin was adapted as a military propellant for use in rifles. Nitroglycerin
continues to be used in military weapons, as a gellatinizer for nitrocellulose, and as an
ingredient in some solid propellants. Nitroglycerin is a popular component of explosives
used in the construction and demolition industries. Nitroglycerin also has medicinal uses;
it has been used for treatment of heart and certain blood-circulation diseases.
Nitroglycerin is one of the most powerful explosives, with blast effects
comparable with those of RDX and PETN (discussed in “PETN” section). Nitroglycerin
is extremely sensitive to shock; even slight physical jarring can cause it to initiate. In
addition, nitroglycerin decomposes over time to even more unstable forms. Nitroglycerin
is, therefore, extremely dangerous to use or even transport. Due to its high degree of
sensitivity (Table 6.1), nitroglycerin is rarely used alone as an explosive. As a result of
numerous catastrophic accidents (Central Pacific, 2005), liquid nitroglycerin has been
widely banned. More stable explosives such as dynamite and related mixtures have been
prepared by mixing nitroglycerin with inert absorbents (diatomaceous earth, sawdust,
etc.)
Dynamite consists of three parts nitroglycerin, one part diatomaceous earth (i.e., a
naturally occurring, chalklike sedimentary rock) and a small amount of sodium
carbonate. This mixture was formulated in 1867 by Alfred Nobel, who was concerned
with the sensitivity and occupational hazards of nitroglycerin. He discovered that
nitroglycerin could be absorbed into a porous material and become much safer to handle
than liquid nitroglycerin alone. As noted above, nitroglycerin is highly shock-sensitive;
however, when adsorbed onto sawdust or diatomaceous earth, it becomes significantly
less sensitive. Today, dynamite is manufactured by absorbing nitroglycerin in a mixture
of sawdust, wood pulp, starch, and similar carbon-rich materials. Calcium carbonate is
added to neutralize the nitric acid that forms by spontaneous decomposition. Ethylene
glycol dinitrate is added as an antifreeze and oxidizers are also typically added. The
mixture is commonly formed into short sticks and wrapped in waxed paper; another
popular configuration is as cast boosters.
By virtue of its enhanced stability over nitroglycerin, dynamite may be
transported and used with less hazard of spontaneous detonation. Dynamite is so
insensitive that a detonating cap is required to initiate it. Regardless, however, dynamite
is considered to be sensitive to heat, shock, and friction and must be handled with
extreme care. Aged dynamite can be quite hazardous. Old dynamite sticks that appear to
be sweating, with salt crystals forming on the outside of the package, dark stains
appearing on the package cover, or liquid collecting at the base of a cartridge, indicate the
presence of nitroglycerin that has leached from the dynamite. Such a scenario is
extremely dangerous and highly susceptible to initiation. Workers engaged in the
production or use of dynamite, or those touching or inhaling fumes from dynamite may
become exposed to vapors of nitroglycerin and/or ethylene glycol dinitrate. Initial
exposure often results in an intense headache and in some cases dizziness, nausea,
palpitations, and decrease in blood pressure. These initial symptoms indicate a shift in
blood volume from the central to the peripheral circulatory system initiated by dilation of
blood vessels.
In 1956, a new blasting agent was developed using a mixture of ammonium
nitrate, aluminum powder, and water. The safety and efficiency of this new agent was
soon apparent, and subsequent research resulted in the development of slurry explosives
and eventually to dry explosive agents. Ammonium nitrate (chemical formula NH4NO3),
is a simple salt and a common commercial fertilizer. Mixed with fuel oil and confined,
this material can be transformed into a powerful high explosive. ANFO has a broad range
of detonation velocities, depending on the reference cited. An approximation for large
quantities of blasting agent is roughly half the detonation velocity of C-4, or about 13,000
ft/s (Global Security, 2008). ANFO blasting agents are among the most common
industrial explosives used in the United States. ANFO has essentially replaced dynamite
for bench blasting during surface mining and quarrying. The most widely used dry
blasting agent is a mixture of ammonium nitrate prills and fuel oil.
Military explosives are not readily available to civilians; however, thefts have
occurred, resulting in their incorporation in improvised bombs. For responders, these
explosives should be handled with the same safety precautions as those used with
commercial explosives. RDX is a nitramine compound (chemical formula 1,3,5-trinitro-
1,3,5-triazine) whose structure is a heterocycle (Figure 6.11). Several explanations exist
for the term RDX, including Royal Demolition Explosive, Research Department
Composition X, and Research Department Explosive (Cocroft, 2000). It is more
commonly known as cyclonite or hexogen. RDX was used widely during World War II
because petroleum was not required as a raw ingredient. Since World War II, RDX has
become the second most widely used high explosive in the military, exceeded only by
TNT. RDX is typically used in mixtures with other explosives, oils, or waxes. It is
considered the most powerful and brisant of the military high explosives (see Box 6.4).
RDX is second in strength to nitroglycerin among common explosive substances. When
compressed to a density of 1.70 g/cm3 , it has a confined detonation velocity of about
27,000 ft/s.
Pure explosive compounds may be used alone as liquids, powders, or solid casts;
however, the majority of explosives require modification to their physical properties. To
alter mechanical as well as other properties, pure explosives are blended with other
explosives and with inert materials. In the context of explosives, the term plastic indicates
a malleable or moldable material, similar to properties of modeling clay (Figure 6.14).
Explosives are mixed with a plastic binder and a plasticizer to keep the material from
hardening. Several plastic explosives have been popular among military engineers and for
commercial (particularly industrial) uses. The most common commercial use of plastic
explosives is for hardening high manganese percentage steel (PA&E, 2006). For the
emergency responder, it should be noted that the ability of plastic explosives to conform
to numerous shapes, while maintaining their destructive capabilities, make them ideal
weapons for IEDs for terrorists.
C-4 (Composition 4) is a plastic explosive primarily used as a demolition charge,
and to cut through steel (Figure 6.14). C-4 is a simple mixture composed of explosives,
plasticizer, and binder. As is common with many plastic explosives, the energetic
ingredient in C-4 is RDX, comprising about 90% of the C-4 by weight. This formulation
also contains about 5% 2-ethylhexyl sebacate (the plasticizer), 2% polyisobutylene (the
binder), and 2% motor oil. C-4 detonates with a blast wave of approximately 8040 m/s
(26,400 ft/s). For successful detonation, C-4 requires the heat generated by the shock of a
special military blasting cap. Commercial blasting caps are typically not powerful enough
to detonate C-4. When molding C-4, cracks may form in the solid mass. These cracks
will prevent the complete detonation of the charge and may result in scattering of a
portion of unused explosive. Such a phenomenon is termed a low-order explosion, that is,
an incomplete detonation. Under such a situation, hazardous material will persist on site,
which may be susceptible to accidental detonation.
Semtex is another popular malleable explosive, with characteristics and uses
similar to those of C-4. Semtex was first manufactured by the Semtin East Bohemian
Chemical Works in the Czech Republic. It is used in commercial blasting, demolition,
and in certain military applications. As with C-4, Semtex can be used to cut through thick
steel. Semtex uses high explosive (PETN mixed with RDX), combined with a binder of a
synthetic styrene–butadiene rubber binder, resulting in a malleable product. Semtex is
brick-orange in color, whereas C-4 is off-white. Semtex has the benefit of being usable
over a greater temperature range than other plastic explosives. The two common varieties
of Semtex are A (for blasting) and H (for hardening).
Cast explosives typically are shaped within cardboard, plastic, or metal
packaging. An example of a cast explosive is dynamite (see Figure 6.9). Cast explosives
are relatively insensitive and normally consist of multiple components. A responder
should never assume that cast explosives only exist with their exterior packaging intact—
such explosives do not require packaging. Unexploded artillery and mortar projectiles
have been stolen from ranges at military bases, cut open, and the cast explosives removed
and used in IEDs. Also known as plastic-bonded explosives (PBX), Detasheet or Flex-x,
sheet explosives consist of a mixture of PETN or RDX, and a plastic polymer such as
polystyrene. By virtue of its flexibility, its major use is as a cutting charge for irregular
surfaces. In sheet explosive, the fine explosive particles are embedded in a rubbery
binder. The combination of explosive and polymer is extruded into rolls, sheets, ribbons,
and cord. The sheets measure between 1 and 8 mm thick and are available in rolls with
inner layers of waxed paper preventing adhesion of the explosives (Figure 6.15). Sheet
explosives for military use are manufactured in olive drab color; however, commercial
sheet explosives may be found in any color.
An emulsion is composed of a mixture of two immiscible liquids, that is, those
that do not normally mix with one another. One liquid is typically oil-based, whereas the
other is water-based. When the appropriate emulsifier is included in the mixture, the two
phases blend well together. Emulsion explosives are prepared as water-in-oil emulsions.
One phase is composed of an oxidizer salt solution (e.g., ammonium nitrate) suspended
as microscopic-sized droplets surrounded by a continuous fuel phase. An emulsifying
agent stabilizes the mixture. As each microcell of the oxidizer is coated with an oily
exterior, the emulsion has excellent water resistance. A bulking agent such as ultrafine air
bubbles may be dispersed throughout the emulsion matrix, which modifies the sensitivity
of the explosive (Zukovich, 2008). Many fuels are incorporated in emulsion explosives,
including water-soluble organics such as glycol and alcohols. Some emulsion explosives
have a high content of aluminum powder that increases the overall explosive force and
imparts a shiny metallic color when the contents are exposed.
G. Effects of an Explosion
The severity of an explosion is a function of the type of explosive (e.g.,
detonation velocity, degree of brisance), the amount of explosive material involved, and
conditions of the explosion (i.e., whether material was confined, proximity to structures).
The first phase of an explosion involves the instantaneous formation of the characteristic
blast (shock) wave. Shock waves can result in widespread damage to the surroundings,
including structures and populations. In the blast phase, the detonation generates gases
under high pressure (up to several thousand psi) and high temperatures (approximately
3000–4000°C). The hot gas expands, forcing out the volume it occupies. A layer of
compressed air (the blast wave), containing most of the energy released by the explosion,
consequently forms in front of this gas volume. The pressure of the blast wave
instantaneously increases to a value well above the ambient atmospheric pressure. This
overpressure can reach as high as hundreds of pounds per square inch. The overpressure
is sufficient to destroy structures and cause severe injuries and death.
The blast wave travels outward like the ripple created by a stone dropped into a
pond. The initial blast of outward pressure is called the positive phase of the blast. The
side-on overpressure rapidly decays as the shock wave expands outward from the
explosion source. When pressure from the positive phase extends outward a partial
vacuum is created at the seat of the blast. This negative pressure is short-lived and is
quickly filled by outside pressure after the blast subsides. Air is rapidly sucked back into
the blast seat. This effect is the so-called negative phase of the explosion, and the refilling
effect is termed implosion. Implosion is the rapid equalizing of the surrounding air
pressure. The negative phase is accompanied by high winds that carry the debris from
long distances back into the original blast area. Implosion may last three times longer
than the initial explosion.
The second phase of an explosion is the fragmentation phase. In this phase, the
container of the exploding material is destroyed. Nearby objects are broken to pieces and
thrown outward in all directions. Many injuries received from an explosion are
fragmentation wounds. The final phase of an explosion is the thermal effect phase. This
phase involves the release of heat generated from the blast. The rate of heat release and
the temperature depend on the explosive material involved, the distance from the blast,
and the detonation velocity. Thermal effects can result in severe skin burns, death, and
damage to materials such as metals, glass, and polymers.
IED is a term used to describe a home-made bomb. Many are made from simple,
readily available materials such as steel or polyvinyl chloride (PVC) pipes, standard
electrical wiring, home-made switches, and consumer batteries (Figure 6.23). The
explosive charge may contain smokeless powder or ANFO, or a more sensitive
ingredient. Some IEDs are derived from military explosives attached to a detonating
mechanism (Figure 6.24). IEDs are triggered by various methods, including remote
control, infrared or magnetic triggers, pressure-sensitive bars, or trip wires. Most IEDs
contain an electric initiator and, therefore, require an electric power source such as a
battery. Most commercially available batteries can power an initiator. Batteries can be cut
and shaped to make detection more difficult. These consist of blasting caps or flame-
producing components such as fuse igniters. Improvised initiators can be easily
constructed. Examples include a modified flash bulb or a hobby fuse. Initiator
constituents can also be improvised; an example is triacetone triperoxide.
Explosives take many forms in IEDs. Some are manufactured using old
munitions, whereas others contain commercial ingredients (e.g., dynamite). Still others
contain simple ingredients purchased from a local gun store (smokeless powder).
Switches are used as either an arming switch or a fuse and can be simple or complex in
design. More than one switch can be included to create redundancy in the system. The
arming switch is a safety for the IED and works by disarming (i.e., electrically
disengaging) the fusing switch. When the arming switch is engaged, the fusing switch
becomes functional. Designs for switches are essentially unlimited so any action by its
intended target or a first responder could result in detonation. Switches designed
specifically for IEDs can appear quite innocent-looking, completely fitting into the local
surroundings.
