An explosive material, also called an explosive, is a reactive
substance that contains a great amount of potential energy that can
produce an explosion if released suddenly, usually accompanied by the
production of light, heat, sound, and pressure. An explosive charge is
a measured quantity of explosive material, which may be composed of a
single ingredient or a combination of two or more.
The potential energy stored in an explosive material may, for example,
chemical energy, such as nitroglycerin or grain dust
pressurized gas, such as a gas cylinder or aerosol can
nuclear energy, such as in the fissile isotopes uranium-235 and
Explosive materials may be categorized by the speed at which they
expand. Materials that detonate (the front of the chemical reaction
moves faster through the material than the speed of sound) are said to
be "high explosives" and materials that deflagrate are said to be "low
explosives". Explosives may also be categorized by their sensitivity.
Sensitive materials that can be initiated by a relatively small amount
of heat or pressure are primary explosives and materials that are
relatively insensitive are secondary or tertiary explosives.
A wide variety of chemicals can explode; a smaller number are
manufactured specifically for the purpose of being used as explosives.
The remainder are too dangerous, sensitive, toxic, expensive,
unstable, or prone to decomposition or degradation over short time
In contrast, some materials are merely combustible or flammable if
they burn without exploding.
The distinction, however, is not razor-sharp. Certain
materials—dusts, powders, gases, or volatile organic liquids—may
be simply combustible or flammable under ordinary conditions, but
become explosive in specific situations or forms, such as dispersed
airborne clouds, or confinement or sudden release.
Properties of explosive materials
4.2 Sensitivity to initiation
4.3 Velocity of detonation
4.5 Power, performance, and strength
Hygroscopicity and water resistance
4.12 Volume of products of explosion
Oxygen balance (OB% or Ω)
4.14 Chemical composition
4.14.1 Chemically pure compounds
4.14.2 Mixture of oxidizer and fuel
4.15 Availability and cost
5 Classification of explosive materials
5.1 By sensitivity
5.1.1 Primary explosive
5.1.2 Secondary explosive
5.1.3 Tertiary explosive
5.2 By velocity
5.2.1 Low explosives
5.2.2 High explosives
5.3 By composition
5.3.1 Priming composition
5.4 By physical form
5.5 Shipping label classifications
United Nations Organization (UNO) Hazard Class and Division
5.5.2 Class 1 Compatibility Group
6.3 United States
6.3.1 State laws
7 List of explosives
7.3 Elements and isotopes
8 See also
10 Further reading
11 External links
See also: History of gunpowder
At its root, the history of chemical explosives lies in the history of
gunpowder. During the Tang Dynasty in the 9th century, Taoist
Chinese alchemists were eagerly trying to find the elixir of
immortality. In the process, they stumbled upon the explosive
invention of gunpowder made from coal, saltpeter, and sulfur in 1044.
Gunpowder was the first form of chemical explosives and by 1161, the
Chinese were using explosives for the first time in warfare.
The Chinese would incorporate explosives fired from bamboo or bronze
tubes known as bamboo fire crackers. The Chinese also used inserted
rats from inside the bamboo fire crackers to fire toward the enemy,
creating great psychological ramifications – scaring enemy soldiers
away and causing cavalry units to go wild.
Though early thermal weapons, such as Greek fire, have existed since
ancient times, the first widely used explosive in warfare and mining
was black powder, invented in 9th century in China by Song Chinese
alchemists. This material was sensitive to water, and it produced
copious amounts of dark smoke. The first useful explosive stronger
than black powder was nitroglycerin, developed in 1847. Since
nitroglycerin is a liquid and highly unstable, it was replaced by
TNT in 1863, smokeless powder, dynamite in 1867 and
gelignite (the latter two being sophisticated stabilized preparations
of nitroglycerin rather than chemical alternatives, both invented by
World War I
World War I saw the adoption of
TNT trinitrotoluene in
World War II
World War II saw an extensive use of new explosives
(see List of explosives used during World War II). In turn, these have
largely been replaced by more powerful explosives such as C-4 and
PETN. However, C-4 and
PETN react with metal and catch fire easily,
yet unlike TNT, C-4 and
PETN are waterproof and malleable.
A video on safety precautions at blast sites
A video describing how to safely handle explosives in mines.
The largest commercial application of explosives is mining. Whether
the mine is on the surface or is buried underground, the detonation or
deflagration of either a high or low explosive in a confined space can
be used to liberate a fairly specific sub-volume of a brittle material
in a much larger volume of the same or similar material. The mining
industry tends to use nitrate-based explosives such as emulsions of
fuel oil and ammonium nitrate solutions, mixtures of ammonium nitrate
prills (fertilizer pellets) and fuel oil (ANFO) and gelatinous
suspensions or slurries of ammonium nitrate and combustible fuels.
In Materials Science and Engineering, explosives are used in cladding.
A thin plate of some material is placed atop a thick layer of a
different material, both layers typically of metal. Atop the thin
layer is placed an explosive. At one end of the layer of explosive,
the explosion is initiated. The two metallic layers are forced
together at high speed and with great force. The explosion spreads
from the initiation site throughout the explosive. Ideally, this
produces a metallurgical bond between the two layers.
As the length of time the shock wave spends at any point is small, we
can see mixing of the two metals and their surface chemistries,
through some fraction of the depth, and they tend to be mixed in some
way. It is possible that some fraction of the surface material from
either layer eventually gets ejected when the end of material is
reached. Hence, the mass of the now "welded" bilayer, may be less than
the sum of the masses of the two initial layers.
There are applications where a shock wave, and electrostatics, can
result in high velocity projectiles.
See also: Explosives engineering
Main article: Explosives safety
Main article: Chemical explosive
The international pictogram for explosive substances
An explosion is a type of spontaneous chemical reaction that, once
initiated, is driven by both a large exothermic change (great release
of heat) and a large positive entropy change (great quantities of
gases are released) in going from reactants to products, thereby
constituting a thermodynamically favorable process in addition to one
that propagates very rapidly. Thus, explosives are substances that
contain a large amount of energy stored in chemical bonds. The
energetic stability of the gaseous products and hence their generation
comes from the formation of strongly bonded species like carbon
monoxide, carbon dioxide, and (di)nitrogen, which contain strong
double and triple bonds having bond strengths of nearly 1 MJ/mole.
Consequently, most commercial explosives are organic compounds
containing -NO2, -ONO2 and -NHNO2 groups that, when detonated, release
gases like the aforementioned (e.g., nitroglycerin, TNT, HMX, PETN,
An explosive is classified as a low or high explosive according to its
rate of combustion: low explosives burn rapidly (or deflagrate), while
high explosives detonate. While these definitions are distinct, the
problem of precisely measuring rapid decomposition makes practical
classification of explosives difficult.
Traditional explosives mechanics is based on the shock-sensitive rapid
oxidation of carbon and hydrogen to carbon dioxide, carbon monoxide
and water in the form of steam. Nitrates typically provide the
required oxygen to burn the carbon and hydrogen fuel. High explosives
tend to have the oxygen, carbon and hydrogen contained in one organic
molecule, and less sensitive explosives like
ANFO are combinations of
fuel (carbon and hydrogen fuel oil) and ammonium nitrate. A sensitizer
such as powdered aluminum may be added to an explosive to increase the
energy of the detonation. Once detonated, the nitrogen portion of the
explosive formulation emerges as nitrogen gas and toxic nitric oxides.
The chemical decomposition of an explosive may take years, days,
hours, or a fraction of a second. The slower processes of
decomposition take place in storage and are of interest only from a
stability standpoint. Of more interest are the other two rapid forms
besides decomposition: deflagration and detonation.
Main article: Deflagration
In deflagration, decomposition of the explosive material is propagated
by a flame front which moves slowly through the explosive material at
speeds less than the speed of sound within the substance (usually
below 1000 m/s)  in contrast to detonation, which occurs at
speeds greater than the speed of sound.
Deflagration is a
characteristic of low explosive material.
Main article: Detonation
This term is used to describe an explosive phenomenon whereby the
decomposition is propagated by an explosive shock wave traversing the
explosive material at speeds greater than the speed of sound within
the substance. The shock front is capable of passing through the
high explosive material at supersonic speeds, typically thousands of
metres per second.
In addition to chemical explosives, there are a number of more exotic
explosive materials, and exotic methods of causing explosions.
Examples include nuclear explosives, and abruptly heating a substance
to a plasma state with a high-intensity laser or electric arc.
Laser- and arc-heating are used in laser detonators,
exploding-bridgewire detonators, and exploding foil initiators, where
a shock wave and then detonation in conventional chemical explosive
material is created by laser- or electric-arc heating.
electric energy are not currently used in practice to generate most of
the required energy, but only to initiate reactions.
Properties of explosive materials
To determine the suitability of an explosive substance for a
particular use, its physical properties must first be known. The
usefulness of an explosive can only be appreciated when the properties
and the factors affecting them are fully understood. Some of the more
important characteristics are listed below:
Main article: Sensitivity (explosives)
Sensitivity refers to the ease with which an explosive can be ignited
or detonated, i.e., the amount and intensity of shock, friction, or
heat that is required. When the term sensitivity is used, care must be
taken to clarify what kind of sensitivity is under discussion. The
relative sensitivity of a given explosive to impact may vary greatly
from its sensitivity to friction or heat. Some of the test methods
used to determine sensitivity relate to:
Impact — Sensitivity is expressed in terms of the distance through
which a standard weight must be dropped onto the material to cause it
Friction — Sensitivity is expressed in terms of what occurs when a
weighted pendulum scrapes across the material (it may snap, crackle,
ignite, and/or explode).
Heat — Sensitivity is expressed in terms of the temperature at which
flashing or explosion of the material occurs.
Specific explosives (usually but not always highly sensitive on one or
more of the three above axes) may be idiosyncratically sensitive to
such factors as pressure drop, acceleration, the presence of sharp
edges or rough surfaces, incompatible materials, or even—in rare
cases—nuclear or electromagnetic radiation. These factors present
special hazards that may rule out any practical utility.
Sensitivity is an important consideration in selecting an explosive
for a particular purpose. The explosive in an armor-piercing
projectile must be relatively insensitive, or the shock of impact
would cause it to detonate before it penetrated to the point desired.
The explosive lenses around nuclear charges are also designed to be
highly insensitive, to minimize the risk of accidental detonation.
Sensitivity to initiation
The index of the capacity of an explosive to be initiated into
detonation in a sustained manner. It is defined by the power of the
detonator which is certain to prime the explosive to a sustained and
continuous detonation. Reference is made to the
that consists of a series of 10 detonators, from n. 1 to n. 10, each
of which corresponds to an increasing charge weight. In practice, most
of the explosives on the market today are sensitive to an n. 8
detonator, where the charge corresponds to 2 grams of mercury
Velocity of detonation
The velocity with which the reaction process propagates in the mass of
the explosive. Most commercial mining explosives have detonation
velocities ranging from 1800 m/s to 8000 m/s. Today,
velocity of detonation can be measured with accuracy. Together with
density it is an important element influencing the yield of the energy
transmitted for both atmospheric over-pressure and ground
acceleration. By definition, a "low explosive," such as black powder,
or smokeless gunpowder has a burn rate of 171–631 m/s. In
contrast, a "high explosive," whether a primary, such as detonating
cord, or a secondary, such as
TNT or C-4 has a significantly higher
Main article: Chemical stability
Stability is the ability of an explosive to be stored without
The following factors affect the stability of an explosive:
Chemical constitution. In the strictest technical sense, the word
"stability" is a thermodynamic term referring to the energy of a
substance relative to a reference state or to some other substance.
However, in the context of explosives, stability commonly refers to
ease of detonation, which is concerned with kinetics (i.e., rate of
decomposition). It is perhaps best, then, to differentiate between the
terms thermodynamically stable and kinetically stable by referring to
the former as "inert." Contrarily, a kinetically unstable substance is
said to be "labile." It is generally recognized that certain groups
like nitro (–NO2), nitrate (–ONO2), and azide (–N3), are
intrinsically labile. Kinetically, there exists a low activation
barrier to the decomposition reaction. Consequently, these compounds
exhibit high sensitivity to flame or mechanical shock. The chemical
bonding in these compounds is characterized as predominantly covalent
and thus they are not thermodynamically stabilized by a high
ionic-lattice energy. Furthermore, they generally have positive
enthalpies of formation and there is little mechanistic hindrance to
internal molecular rearrangement to yield the more thermodynamically
stable (more strongly bonded) decomposition products. For example, in
lead azide, Pb(N3)2, the nitrogen atoms are already bonded to one
another, so decomposition into Pb and N2 is relatively easy.
Temperature of storage. The rate of decomposition of explosives
increases at higher temperatures. All standard military explosives may
be considered to have a high degree of stability at temperatures from
–10 to +35 °C, but each has a high temperature at which its
rate of decomposition rapidly accelerates and stability is reduced. As
a rule of thumb, most explosives become dangerously unstable at
temperatures above 70 °C.
Exposure to sunlight. When exposed to the ultraviolet rays of
sunlight, many explosive compounds containing nitrogen groups rapidly
decompose, affecting their stability.
Electrostatic or spark sensitivity to initiation
is common in a number of explosives. Static or other electrical
discharge may be sufficient to cause a reaction, even detonation,
under some circumstances. As a result, safe handling of explosives and
pyrotechnics usually requires proper electrical grounding of the
Power, performance, and strength
Power (physics) and Strength (explosive)
The term power or performance as applied to an explosive refers to its
ability to do work. In practice it is defined as the explosive's
ability to accomplish what is intended in the way of energy delivery
(i.e., fragment projection, air blast, high-velocity jet, underwater
shock and bubble energy, etc.).
Explosive power or performance is
evaluated by a tailored series of tests to assess the material for its
intended use. Of the tests listed below, cylinder expansion and
air-blast tests are common to most testing programs, and the others
support specific applications.
Cylinder expansion test. A standard amount of explosive is loaded into
a long hollow cylinder, usually of copper, and detonated at one end.
Data is collected concerning the rate of radial expansion of the
cylinder and the maximum cylinder wall velocity. This also establishes
the Gurney energy or 2E.
Cylinder fragmentation. A standard steel cylinder is loaded with
explosive and detonated in a sawdust pit. The fragments are collected
and the size distribution analyzed.
Detonation pressure (Chapman–Jouguet condition).
data derived from measurements of shock waves transmitted into water
by the detonation of cylindrical explosive charges of a standard size.
Determination of critical diameter. This test establishes the minimum
physical size a charge of a specific explosive must be to sustain its
own detonation wave. The procedure involves the detonation of a series
of charges of different diameters until difficulty in detonation wave
propagation is observed.
Massive-diameter detonation velocity.
Detonation velocity is dependent
on loading density (c), charge diameter, and grain size. The
hydrodynamic theory of detonation used in predicting explosive
phenomena does not include the diameter of the charge, and therefore a
detonation velocity, for a massive diameter. This procedure requires
the firing of a series of charges of the same density and physical
structure, but different diameters, and the extrapolation of the
resulting detonation velocities to predict the detonation velocity of
a charge of a massive diameter.
Pressure versus scaled distance. A charge of a specific size is
detonated and its pressure effects measured at a standard distance.
The values obtained are compared with those for TNT.
Impulse versus scaled distance. A charge of a specific size is
detonated and its impulse (the area under the pressure-time curve)
measured as a function of distance. The results are tabulated and
Relative bubble energy (RBE). A 5 to 50 kg charge is detonated in
water and piezoelectric gauges measure peak pressure, time constant,
impulse, and energy.
The RBE may be defined as Kx 3
RBE = Ks
where K = the bubble expansion period for an experimental (x) or a
standard (s) charge.
Main article: Brisance
In addition to strength, explosives display a second characteristic,
which is their shattering effect or brisance (from the French meaning
to "break"), which is distinguished and separate from their total work
capacity. This characteristic is of practical importance in
determining the effectiveness of an explosion in fragmenting shells,
bomb casings, grenades, and the like. The rapidity with which an
explosive reaches its peak pressure (power) is a measure of its
Brisance values are primarily employed in France and Russia.
The sand crush test is commonly employed to determine the relative
brisance in comparison to TNT. No test is capable of directly
comparing the explosive properties of two or more compounds; it is
important to examine the data from several such tests (sand crush,
trauzl, and so forth) in order to gauge relative brisance. True values
for comparison require field experiments.
Density of loading refers to the mass of an explosive per unit volume.
Several methods of loading are available, including pellet loading,
cast loading, and press loading, the choice being determined by the
characteristics of the explosive. Dependent upon the method employed,
an average density of the loaded charge can be obtained that is within
80–99% of the theoretical maximum density of the explosive. High
load density can reduce sensitivity by making the mass more resistant
to internal friction. However, if density is increased to the extent
that individual crystals are crushed, the explosive may become more
sensitive. Increased load density also permits the use of more
explosive, thereby increasing the power of the warhead. It is possible
to compress an explosive beyond a point of sensitivity, known also as
dead-pressing, in which the material is no longer capable of being
reliably initiated, if at all.
Volatility is the readiness with which a substance vaporizes.
Excessive volatility often results in the development of pressure
within rounds of ammunition and separation of mixtures into their
constituents. Volatility affects the chemical composition of the
explosive such that a marked reduction in stability may occur, which
results in an increase in the danger of handling.
Hygroscopicity and water resistance
The introduction of water into an explosive is highly undesirable
since it reduces the sensitivity, strength, and velocity of detonation
of the explosive.
Hygroscopicity is a measure of a material's
moisture-absorbing tendencies. Moisture affects explosives adversely
by acting as an inert material that absorbs heat when vaporized, and
by acting as a solvent medium that can cause undesired chemical
reactions. Sensitivity, strength, and velocity of detonation are
reduced by inert materials that reduce the continuity of the explosive
mass. When the moisture content evaporates during detonation, cooling
occurs, which reduces the temperature of reaction. Stability is also
affected by the presence of moisture since moisture promotes
decomposition of the explosive and, in addition, causes corrosion of
the explosive's metal container.
Explosives considerably differ from one another as to their behavior
in the presence of water. Gelatin dynamites containing nitroglycerine
have a degree of water resistance. Explosives based on ammonium
nitrate have little or no water resistance due to the reaction between
ammonium nitrate and water, which liberates ammonia, nitrogen dioxide
and hydrogen peroxide. In addition, ammonium nitrate is hygroscopic,
susceptible to damp, hence the above concerns.
Many explosives are toxic to some extent. Manufacturing inputs can
also be organic compounds or hazardous materials that require special
handing due to risks (such as carcinogens). The decomposition
products, residual solids, or gases of some explosives can be toxic,
whereas others are harmless, such as carbon dioxide and water.
Examples of harmful by-products are:
Heavy metals, such as lead, mercury, and barium from primers (observed
in high-volume firing ranges)
Nitric oxides from TNT
Perchlorates when used in large quantities
"Green explosives" seek to reduce environment and health impacts. An
example of such is the lead-free primary explosive copper(I)
5-nitrotetrazolate, an alternative to lead azide. One variety of a
green explosive is CDP explosives, whose synthesis does not involve
any toxic ingredients, consumes carbon dioxide while detonating and
does not release any nitric oxides into the atmosphere when used.
Explosive material may be incorporated in the explosive train of a
device or system. An example is a pyrotechnic lead igniting a booster,
which causes the main charge to detonate.
Volume of products of explosion
The most widely used explosives are condensed liquids or solids
converted to gaseous products by explosive chemical reactions and the
energy released by those reactions. The gaseous products of complete
reaction are typically carbon dioxide, steam, and nitrogen.
Gaseous volumes computed by the ideal gas law tend to be too large at
high pressures characteristic of explosions. Ultimate volume
expansion may be estimated at three orders of magnitude, or one liter
per gram of explosive. Explosives with an oxygen deficit will generate
soot or gases like carbon monoxide and hydrogen, which may react with
surrounding materials such as atmospheric oxygen. Attempts to
obtain more precise volume estimates must consider the possibility of
such side reactions, condensation of steam, and aqueous solubility of
gases like carbon dioxide.
By comparison, CDP detonation is based on the rapid reduction of
carbon dioxide to carbon with the abundant release of energy. Rather
than produce typical waste gases like carbon dioxide, carbon monoxide,
nitrogen and nitric oxides, CDP is different. Instead, the highly
energetic reduction of carbon dioxide to carbon vaporizes and
pressurizes excess dry ice at the wave front, which is the only gas
released from the detonation. The velocity of detonation for CDP
formulations can therefore be customized by adjusting the weight
percentage of reducing agent and dry ice. Interestingly, CDP
detonations produce a large amount of solid materials that can have
great commercial value as an abrasive:
Example – CDP
Detonation Reaction with Magnesium: XCO2 + 2Mg →
2MgO + C + (X-1)CO2
The products of detonation in this example are magnesium oxide, carbon
in various phases including diamond, and vaporized excess carbon
dioxide that was not consumed by the amount of magnesium in the
Oxygen balance (OB% or Ω)
Oxygen balance is an expression that is used to indicate the degree to
which an explosive can be oxidized. If an explosive molecule contains
just enough oxygen to convert all of its carbon to carbon dioxide, all
of its hydrogen to water, and all of its metal to metal oxide with no
excess, the molecule is said to have a zero oxygen balance. The
molecule is said to have a positive oxygen balance if it contains more
oxygen than is needed and a negative oxygen balance if it contains
less oxygen than is needed. The sensitivity, strength, and
brisance of an explosive are all somewhat dependent upon oxygen
balance and tend to approach their maxima as oxygen balance approaches
Oxygen balance applies to traditional explosives mechanics with the
assumption that carbon is oxidized to carbon monoxide and carbon
dioxide during detonation. In what seems like a paradox to an
explosives expert, Cold
Physics uses carbon in its most
highly oxidized state as the source of oxygen in the form of carbon
Oxygen balance, therefore, either does not apply to a CDP
formulation or must be calculated without including the carbon in the
A chemical explosive may consist of either a chemically pure compound,
such as nitroglycerin, or a mixture of a fuel and an oxidizer, such as
black powder or grain dust and air.
Chemically pure compounds
Some chemical compounds are unstable in that, when shocked, they
react, possibly to the point of detonation. Each molecule of the
compound dissociates into two or more new molecules (generally gases)
with the release of energy.
Nitroglycerin: A highly unstable and sensitive liquid
Acetone peroxide: A very unstable white organic peroxide
TNT: Yellow insensitive crystals that can be melted and cast without
Cellulose nitrate: A nitrated polymer which can be a high or low
explosive depending on nitration level and conditions
RDX, PETN, HMX: Very powerful explosives which can be used pure or in
C-4 (or Composition C-4): An
RDX plastic explosive plasticized to be
adhesive and malleable
The above compositions may describe most of the explosive material,
but a practical explosive will often include small percentages of
other substances. For example, dynamite is a mixture of highly
sensitive nitroglycerin with sawdust, powdered silica, or most
commonly diatomaceous earth, which act as stabilizers. Plastics and
polymers may be added to bind powders of explosive compounds; waxes
may be incorporated to make them safer to handle; aluminium powder may
be introduced to increase total energy and blast effects. Explosive
compounds are also often "alloyed":
RDX powders may be mixed
(typically by melt-casting) with
TNT to form
Octol or Cyclotol.
Mixture of oxidizer and fuel
An oxidizer is a pure substance (molecule) that in a chemical reaction
can contribute some atoms of one or more oxidizing elements, in which
the fuel component of the explosive burns. On the simplest level, the
oxidizer may itself be an oxidizing element, such as gaseous or liquid
Black powder: Potassium nitrate, charcoal and sulfur
Flash powder: Fine metal powder (usually aluminium or magnesium) and a
strong oxidizer (e.g. potassium chlorate or perchlorate)
Ammonium nitrate and aluminium powder
Potassium chlorate and red phosphorus. This is a
very sensitive mixture. It is a primary high explosive in which sulfur
is substituted for some or all of the phosphorus to slightly decrease
Detonation Physics: Combinations of carbon dioxide in the form of
dry ice (an untraditional oxygen source), and powdered reducing agents
(fuel) like magnesium and aluminum.
Sprengel explosives: A very general class incorporating any strong
oxidizer and highly reactive fuel, although in practice the name was
most commonly applied to mixtures of chlorates and nitroaromatics.
Ammonium nitrate and fuel oil
Cheddites: Chlorates or perchlorates and oil
Oxyliquits: Mixtures of organic materials and liquid oxygen
Panclastites: Mixtures of organic materials and dinitrogen tetroxide
Availability and cost
The availability and cost of explosives are determined by the
availability of the raw materials and the cost, complexity, and safety
of the manufacturing operations.
Classification of explosive materials
A primary explosive is an explosive that is extremely sensitive to
stimuli such as impact, friction, heat, static electricity, or
electromagnetic radiation. Some primary explosives are also known as
contact explosives. A relatively small amount of energy is required
for initiation. As a very general rule, primary explosives are
considered to be those compounds that are more sensitive than PETN. As
a practical measure, primary explosives are sufficiently sensitive
that they can be reliably initiated with a blow from a hammer;
PETN can also usually be initiated in this manner, so this is
only a very broad guideline. Additionally, several compounds, such as
nitrogen triiodide, are so sensitive that they cannot even be handled
Nitrogen triiodide is so sensitive that it can be
reliably detonated by exposure to alpha radiation; it is the only
explosive for which this is true.
Primary explosives are often used in detonators or to trigger larger
charges of less sensitive secondary explosives. Primary explosives are
commonly used in blasting caps and percussion caps to translate a
physical shock signal. In other situations, different signals such as
electrical or physical shock, or, in the case of laser detonation
systems, light, are used to initiate an action, i.e., an explosion. A
small quantity, usually milligrams, is sufficient to initiate a larger
charge of explosive that is usually safer to handle.
Examples of primary high explosives are:
Alkali metal ozonides
Nitrate (or CPN)
Diethyl ether peroxide
Hexamethylene triperoxide diamine
Methyl ethyl ketone peroxide
Nickel hydrazine nitrate
Nickel hydrazine perchlorate
Tetraamine copper complexes
Oxides of xenon:
A secondary explosive is less sensitive than a primary explosive and
requires substantially more energy to be initiated. Because they are
less sensitive, they are usable in a wider variety of applications and
are safer to handle and store.
Secondary explosives are used in larger
quantities in an explosive train and are usually initiated by a
smaller quantity of a primary explosive.
Examples of secondary explosives include
TNT and RDX.
Tertiary explosives, also called blasting agents, are so insensitive
to shock that they cannot be reliably detonated by practical
quantities of primary explosive, and instead require an intermediate
explosive booster of secondary explosive. These are often used for
safety and the typically lower costs of material and handling. The
largest consumers are large-scale mining and construction operations.
ANFO is an example of a tertiary explosive.
Low explosives are compounds where the rate of decomposition proceeds
through the material at less than the speed of sound. The
decomposition is propagated by a flame front (deflagration) which
travels much more slowly through the explosive material than a shock
wave of a high explosive. Under normal conditions, low explosives
undergo deflagration at rates that vary from a few centimetres per
second to approximately 400 metres per second. It is possible for them
to deflagrate very quickly, producing an effect similar to a
detonation. This can happen under higher pressure or temperature,
which usually occurs when ignited in a confined space.[citation
A low explosive is usually a mixture of a combustible substance and an
oxidant that decomposes rapidly (deflagration); however, they burn
more slowly than a high explosive, which has an extremely fast burn
Low explosives are normally employed as propellants. Included in this
group are petroleum products such as propane and gasoline, gunpowder
(both black and smokeless), and light pyrotechnics, such as flares and
fireworks, but can replace high explosives in certain applications,
see gas pressure blasting.
High explosives (HE) are explosive materials that detonate, meaning
that the explosive shock front passes through the material at a
supersonic speed. High explosives detonate with explosive velocity
ranging from 3 to 9 km/s. For instance,
TNT has a detonation
(burn) rate of approximately 5.8 km/s (19,000 feet per second),
Detonating cord of 6.7 km/s (22,000 feet per second), and C-4
about 8.5 km/s (29,000 feet per second). They are normally
employed in mining, demolition, and military applications. They can be
divided into two explosives classes differentiated by sensitivity:
primary explosive and secondary explosive. The term high explosive is
in contrast with the term low explosive, which explodes (deflagrates)
at a lower rate.
Countless high-explosive compounds are chemically possible, but
commercially and militarily important ones have included NG, TNT, TNX,
RDX, HMX, PETN, TATB, and HNS.
Priming compositions are primary explosives mixed with other
compositions to control (lessen) the sensitivity of the mixture to the
For example, primary explosives are so sensitive that they need to be
stored and shipped in a wet state to prevent accidental initiation.
By physical form
Main article: Use forms of explosives
Explosives are often characterized by the physical form that the
explosives are produced or used in. These use forms are commonly
Plastic or polymer bonded
Putties (AKA plastic explosives)
Slurries and gels
Shipping label classifications
Shipping labels and tags may include both
United Nations and national
United Nations markings include numbered Hazard Class and Division
(HC/D) codes and alphabetic Compatibility Group codes. Though the two
are related, they are separate and distinct. Any Compatibility Group
designator can be assigned to any Hazard Class and Division. An
example of this hybrid marking would be a consumer firework, which is
labeled as 1.4G or 1.4S.
Examples of national markings would include United States Department
of Transportation (U.S. DOT) codes.
United Nations Organization (UNO) Hazard Class and Division
Explosives warning sign
See also: HAZMAT Class 1 Explosives
The Hazard Class and Division (HC/D) is a numeric designator within a
hazard class indicating the character, predominance of associated
hazards, and potential for causing personnel casualties and property
damage. It is an internationally accepted system that communicates
using the minimum amount of markings the primary hazard associated
with a substance.
Listed below are the Divisions for Class 1 (Explosives):
Detonation Hazard. With HC/D 1.1, it is expected that if one
item in a container or pallet inadvertently detonates, the explosion
will sympathetically detonate the surrounding items. The explosion
could propagate to all or the majority of the items stored together,
causing a mass detonation. There will also be fragments from the
item's casing and/or structures in the blast area.
1.2 Non-mass explosion, fragment-producing. HC/D 1.2 is further
divided into three subdivisions, HC/D 1.2.1, 1.2.2 and 1.2.3, to
account for the magnitude of the effects of an explosion.
Mass fire, minor blast or fragment hazard. Propellants and many
pyrotechnic items fall into this category. If one item in a package or
stack initiates, it will usually propagate to the other items,
creating a mass fire.
1.4 Moderate fire, no blast or fragment. HC/D 1.4 items are listed in
the table as explosives with no significant hazard. Most small arms
ammunition (including loaded weapons) and some pyrotechnic items fall
into this category. If the energetic material in these items
inadvertently initiates, most of the energy and fragments will be
contained within the storage structure or the item containers
1.5 mass detonation hazard, very insensitive.
1.6 detonation hazard without mass detonation hazard, extremely
To see an entire UNO Table, browse Paragraphs 3-8 and 3-9 of NAVSEA OP
5, Vol. 1, Chapter 3.
Class 1 Compatibility Group
Compatibility Group codes are used to indicate storage compatibility
for HC/D Class 1 (explosive) materials. Letters are used to designate
13 compatibility groups as follows.
Primary explosive substance (1.1A).
B: An article containing a primary explosive substance and not
containing two or more effective protective features. Some articles,
such as detonator assemblies for blasting and primers, cap-type, are
included. (1.1B, 1.2B, 1.4B).
Propellant explosive substance or other deflagrating explosive
substance or article containing such explosive substance (1.1C, 1.2C,
1.3C, 1.4C). These are bulk propellants, propelling charges, and
devices containing propellants with or without means of ignition.
Examples include single-based propellant, double-based propellant,
triple-based propellant, and composite propellants, solid propellant
rocket motors and ammunition with inert projectiles.
D: Secondary detonating explosive substance or black powder or article
containing a secondary detonating explosive substance, in each case
without means of initiation and without a propelling charge, or
article containing a primary explosive substance and containing two or
more effective protective features. (1.1D, 1.2D, 1.4D, 1.5D).
E: Article containing a secondary detonating explosive substance
without means of initiation, with a propelling charge (other than one
containing flammable liquid, gel or hypergolic liquid) (1.1E, 1.2E,
F containing a secondary detonating explosive substance with its means
of initiation, with a propelling charge (other than one containing
flammable liquid, gel or hypergolic liquid) or without a propelling
charge (1.1F, 1.2F, 1.3F, 1.4F).
G: Pyrotechnic substance or article containing a pyrotechnic
substance, or article containing both an explosive substance and an
illuminating, incendiary, tear-producing or smoke-producing substance
(other than a water-activated article or one containing white
phosphorus, phosphide or flammable liquid or gel or hypergolic liquid)
(1.1G, 1.2G, 1.3G, 1.4G). Examples include Flares, signals, incendiary
or illuminating ammunition and other smoke and tear producing devices.
H: Article containing both an explosive substance and white phosphorus
(1.2H, 1.3H). These articles will spontaneously combust when exposed
to the atmosphere.
J: Article containing both an explosive substance and flammable liquid
or gel (1.1J, 1.2J, 1.3J). This excludes liquids or gels which are
spontaneously flammable when exposed to water or the atmosphere, which
belong in group H. Examples include liquid or gel filled incendiary
ammunition, fuel-air explosive (FAE) devices, and flammable liquid
K: Article containing both an explosive substance and a toxic chemical
agent (1.2K, 1.3K)
Explosive substance or article containing an explosive substance and
presenting a special risk (e.g., due to water-activation or presence
of hypergolic liquids, phosphides, or pyrophoric substances) needing
isolation of each type (1.1L, 1.2L, 1.3L). Damaged or suspect
ammunition of any group belongs in this group.
N: Articles containing only extremely insensitive detonating
S: Substance or article so packed or designed that any hazardous
effects arising from accidental functioning are limited to the extent
that they do not significantly hinder or prohibit fire fighting or
other emergency response efforts in the immediate vicinity of the
The legality of possessing or using explosives varies by jurisdiction.
Various countries around the world have enacted explosives law and
require licenses to manufacture, distribute, store, use, possess
explosives or ingredients.
In the Netherlands, the civil and commercial use of explosives is
covered under the Wet explosieven voor civiel gebruik (explosives for
civil use Act), in accordance with EU directive nr. 93/15/EEG
(Dutch). The illegal use of explosives is covered under the Wet Wapens
en Munitie (Weapons and Munition Act) (Dutch).
Explosive Substances Act 1883
During World War I, numerous laws were created to regulate war related
industries and increase security within the United States. In 1917,
65th United States Congress
65th United States Congress created many laws, including the
Espionage Act of 1917
Espionage Act of 1917 and Explosives Act of 1917.
The Explosives Act of 1917 (session 1, chapter 83,
40 Stat. 385) was signed on 6 October 1917 and went into
effect on 16 November 1917. The legal summary is "An Act to prohibit
the manufacture, distribution, storage, use, and possession in time of
war of explosives, providing regulations for the safe manufacture,
distribution, storage, use, and possession of the same, and for other
purposes". This was the first federal regulation of licensing
explosives purchases. The act was deactivated after World War I
After the United States entered World War II, the Explosives Act of
1917 was reactivated. In 1947, the act was deactivated by President
Organized Crime Control Act of 1970
Organized Crime Control Act of 1970 (Pub.L. 91–452) transferred
many explosives regulations to the Bureau of Alcohol, Tobacco and
Firearms (ATF) of the Department of Treasury. The bill became
effective in 1971.
Currently, regulations are governed by Title 18 of the United States
Code and Title 27 of the Code of Federal Regulations:
"Importation, Manufacture, Distribution and Storage of Explosive
Materials" (18 U.S.C. Chapter 40).
"Commerce in Explosives" (27 C.F.R. Chapter II, Part 555).
Alabama Code Title 8 Chapter 17 Article 9
Alaska State Code Chapter 11.61.240 & 11.61.250
Arizona State Code Title 13 Chapter 31 Articles 01 through 19
Arkansas State Code Title 5 Chapter 73 Article 108
California Penal Code Title 2 Division 5
Colorado (Colorado statutes are copyrighted and require purchase
Connecticut Statutes Volume 9 Title 29 Chapters 343-355
Delaware Code Title 16 Part VI Chapters 70 & 71
Florida Statutes Title XXXIII Chapter 552
Georgia Code Title 16 Chapter 7 Articles 64-97
Hawaii Administrative Rules Title 12 Subtitle 8 Part 1 Chapter 58 AND
Hawaii Revised Statutes
Illinois Explosives Act 225 ILCS 210
Michigan Penal Code Chapter XXXIII Section 750.200 – 750.212a
Mississippi Code Title 45 Chapter 13 Article 3 Section 101 – 109
New York: Health and safety regulations restrict the quantity of black
powder a person may store and transport.
Wisconsin Chapter 941 Subchapter 4-31
List of explosives
CUA, DCA, AGA
HF, AUF, HGF, PTF, KF, AGF
MonoNitro: NGA, NE, NM, NP, NS, NU
DiNitro: DDNP, DNB, DNEU, DNN, DNP, DNPA, DNPH, DNR, DNPD, DNPA, DNC,
DPS, DPA, EDNP, KDNBF, BEAF
TriNitro: RDX, DATB, TATB, PBS, PBP, TNAL, TNAS, TNB, TNBA, TNC, MC,
TNEF, TNOC, TNOF, TNP, TNT, TNN, TNPG, TNR, BTNEN, BTNEC, Tetryl, SA,
Mononitrates: AN, BAN, CAN, MAN, NAN, UN
Dinitrates: DEGDN, EDDN, EDNA, EGDN, HDN, TEGDN, TAOM
Trinitrates: BTTN, TMOTN, NG
Tetranitrates: ETEN, PETN, TNOC
Hexanitrates: CHN, MHN
Tertiary Amines: NTBR, NTCL, NTI, NTS, SEX, AGN
Azides: CNA, CYA, CLA, CUA, EA, FA, HA, PBA, AGA, NAA, RBA, SEA, SIA,
TEA, TAM, TIA
Tetramines: TZE, TZO, AA
Octamines: OAC, ATA
AP (TATP), CHP, DAP, DBP, DEP, HMTD, MEKP, TBHP
XOTF, XDIO, XTRO, XTEO
Alkali metal ozonides
Fulminating silver (several substances)
Tetramine copper complexes
Aluminum Orphorite, Amatex, Amatol, Armstrong's mixture, ANFO, ANNMAL
Baranol, Baratol, Blackpowder, Blasting gelatin, Butyl tetryl
Composition A, Composition B, Composition C, Composition 1,
Composition 2, Composition 3, Composition 4, Composition 5, Cyclotol
Detonating cord, Dynamite
Tannerit simply, Tannerite, Tovex, Tritonal
Elements and isotopes
Alkaline earth metals
Improvised explosive device
Largest artificial non-nuclear explosions
Orica; largest supplier of commercial explosives
Relative effectiveness factor
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Class 1 Hazmat Placards
Blaster Exchange – Explosives Industry Portal
Journal of Energetic Materials
The Explosives and Weapons Forum
Why high nitrogen density in explosives?
YouTube video demonstrating blast wave in slow motion