By Mr. Federico Canfarini, Deputy Inspector of the State Police and Anti-Sabotage Bomb Squad, Ministry of the Interior, Italy
This article aims at highlighting the activities carried out by a specialized EOD/IEDD operator. The content of the article is based on my experience as an IEDD operator and CBRN defense instructor at the Italian National Police, Genova HQs. In particular, the article focuses on homemade explosives obtained by mixing two or more substances (individually harmless) that can generate highly exothermic chemical reactions capable of self-sustainment and with a high reaction rate as well as reactions that lead to the formation of particularly unstable products that can decompose violently.
The large variety of improvised explosive devices and trigger devices, which also depend on the bomber’s creativity, makes homemade ordnance particularly dangerous as the operator is forced to intervene without knowing the exact composition of the explosive and the triggering mechanism.
In fact, this article is the result of a collection of data, deriving from the writer’s twenty years’ experience in countering explosives and/or aggressive handicrafts, which could be useful both to professionals (bomb squads) and to chemical laboratories operators. Aggressive ordnances are those that cause harm from the release of toxic substances rather than to the explosion itself.
It is possible to find a large variety of potentially dangerous products on the market that range from household cleaning products to common unrefined sugar. Most of these products, taken individually, do not have any explosive risk, but if mixed (in specific proportions) with specific substances they can turn into something potentially uncontrollable. It is therefore extremely difficult to catalogue and predict all the potential hazardous scenarios that could occur when deliberately or unintentionally mixing substances.
What makes the operating environment of an IED/EOD specialist even more complex is the large amount of publicly available information related to IED manufacturing techniques. In fact, a large variety of digital platforms provide information not only on the type of products to be mixed, but also on the quantities, conditions and mixing sequence.
It is crucial for an IEDD operator to understand the main differences between conventional explosives and improvised explosives, especially from a chemical point of view. Ultimately, the information outlined in the article should be able to provide useful information not only in support of response operations, but also for prevention purposes.
The primary activity of bomb disposal expert is to make explosive devices safe. It is important to stress the fact that the professional figure of the EOD operator is defined by specific national and international regulations. The qualification of IEDD operator requires the achievement of the IEDD license upon completion of the NATO course on the approach to Improvised Explosive Device Disposal. The IEDD defines a standardized intervention protocol for the neutralization of explosive devices; the procedure was signed in 1984 by 23 States party to the North Atlantic.
As noted in the previous paragraphs, there is a large number of substances suitable for the creation of an improvised explosive device, but in order to better frame the phenomenon, an attempt should be made to divide them into homogeneous categories by physical and chemical parameters. When it comes to the “oxygen balance” parameter, these mixtures are almost all positive. From the point of view of the chemical characteristics, these are mostly mixtures between a “combustible” and an “oxidizing” substance. In addition to these mixtures, it is also necessary to consider all the chemical substances with a well-identified stoichiometric formula but with little stability with regard to thermal or mechanical solicitations. In regard to the physical state, the following categories of formulations can be predicted:
- Mixtures of solid substances (category S-S): formulations that can mostly produce deflagrations involving solid state reagents. Mixtures of solid substances and liquid substances (category S-L): one of the components (mainly the reducing one) is in the liquid state. The reaction obtained is of a faster type than the one obtainable with the S-S formulation.
- Mixtures of solid substances and gas (category S-G): These formulations are obtained by exploiting the rate of combustion of certain substances in the presence of a oxidizing gas, such as air. These explosive combinations are often obtained as a result of the dispersion of metallic or organic dust in a confined atmosphere and it is therefore difficult to regard them as intentionally produced. A similar case may be a high concentration of oxidizing gas (oxygen, chlorine..) in an environment where easily combustible furniture is present.
- Mixtures of liquid substances (category L-L): These mixtures (e.g. rocket propellants) are easily obtainable by mixing flammable liquids with oxidizing liquids (organic and inorganic peroxides) but have remarkable instable characteristics that can reach the point of self-ignition at the time of mixing.
- Mixtures of liquid substances with gas (category L-G): This category includes all those scenarios involving aerosols of liquid organic material (oils, fuels…) dispersed in air in a confined environment. These mixtures are mostly of involuntary origin and require a thermal trigger to explode (e.g. flamethrowers).
- Gas mixtures (G-G category): They are composed of combustible gases of various kinds mixed with oxidizing gases and are often used in explosive devices.
- Unstable solid substances (category S-I): All those substances that can be obtained more or less voluntarily by mixing seemigly harmless chemical compounds.
Possible formulations
a) Improvised explosive devices Category (S-S)
As already mentioned, this is the most frequent type of improvised explosive device for the simplicity of production and the relative ease of finding the necessary substances. In the field of mixtures between oxidants and reducing agents we can count the following main examples:
1) Oxidant: chlorinated or perchlorate; also called “chlorinated” explosives have been known since 1785 and have been used for their low cost. It is therefore considered appropriate to provide some general information on the use of these substances, in order to produce industrial explosives. Potassium chlorate, the most widely used, does not behave like a real explosive unless it is mixed with easily non-oxidized substances. However, if potassium chlorate is heated quickly, an explosive decomposition reaction may happen.
Sodium chlorate is a substance that behaves very similarly to potassium chlorate. It is a hygroscopic salt. It is sensitive to the action of the impact when mixed with combustible substances.
The most used chlorinated explosives are cheddites. From an industrial point of view, manufacturing chlorinated explosives is relatively simple, this is due to the sensitivity of the chlorate, and because an intimate mixture of the components is not required. First the chlorate is mixed separately, till obtaining a very soft dust, while separately a mixture of nitro compounds, petroleum jelly oil, paraffin or reed oil is prepared in wall-enameled iron boiler heated to 50-60°C. Chlorate dust is then added to the obtained solution thus. The hot plastic mass is laid out on the table, left to cool and beaten with rolling pins in order to obtain granules. With regard to perchlorates, among the most important there are ammonium perchlorate NH4CLO4 and potassium perchlorate KClO4. The first is generally used in some explosive mixtures and propellants, but unfortunately it is also widely used when fabricating handcrafted artefacts. The explosive decomposition equation of ammonium perchlorate is the following:
2NH4CLO4 → 4H2O-N2 – Cl2- 2O2
Potassium perchlorate is much more stable than potassium chlorate, but it can easily explode with the use of an appropriate trigger. If confined, it can detonate violently in case of a combustible substance, such as coal and Sulphur. It decomposes according to the equation:
KClO4 → KCl +2O2
The reducing agents used with this type of oxidizer are numerous but the most common are: Sulphur and sulfur compounds, powdered or fine grain metals, various organic substances of common use (sugars, hydrocarbons and solid fats, polymers, flours, sawdust…). As an example, there are a few simple formulations that may be easily improvised.
Example 1.1: Potassium and Sulfur chlorate: 2KClO3 + 3/2S2 ® 2KCl + 3SO2 Type of explosion: deflagrant or disruptive effects depending on confinement; re-ejection of components: drowning by immersion.
Example1. 2: Potassium Chlorate and Sugar: 8KClO3 + C12H22O11 ® KCl + 12 CO2 + 11 H2O Type of explosion: deflagrant or disruptive effects depending on confinement; availability of components: high; possible inertization: drowning by immersion.
Example 1. 3: Potassium chlorate, Ammonium nitrate and naphthalene; in a ternary mixture of components that react causing an explosion, it is only possible when the decomposition stoichiometry is: KClO3 + NH4NO3+C10H8 ® KCl + N2+ CO2+ H2O Type of explosion: deflagrant or disruptive effects depending on confinement; availability of components: high; possible inertization: drowning by immersion.
Example 1. 4: Potassium and Resin chlorate. In this case, since it was not possible to have a chemical formula defined for the “resin” component, it was decided to treat it as a solid hydrocarbon compound, using the generic formula: n(CH2). The following stoichiometric reaction results: nKClO3 +n(CH2) nKCl + nCO®2 + nH2O The mole has been derived from empirical weight percentages. Explosion typology: disruptive effects depending on confinement; availability of components: high; possible inertization: drowning by immersion. The considerations for the previous example can also be applied to the potassium chlorate and starch mixture.
Example 1. 5: Potassium Chlorate, Nitrate of Protasis, Sugar and Magnesium: KClO3+KNO3+C12H22O11+Mg ®KCl + MgO + CO2 + H2O+NO2+K2O Due to the presence of Mg, it may have unwanted reactions with water, in consequence dispersion with CO2 jets is preferable to drowning.
Example1. 6: Potassium chlorate, Vaseline (as unit CH2), Paraffin (as unit CH2), Pitch (as unit CH2): nKClO3 +n(CH2) nKCl + nCO®2 + nH2O
Example 1. 7: Potassium Chlorate, Sugar, Charcoal and Tar (as unit CH2): KClO3 +n(CH2) 2KCl + nCO®2 + nH2O
Example 1. 8: Potassium Chlorate, Aluminum: KClO3 + 2Al KCl + Al®2O3
The energy developed is: 1496kJ/kg. Type of explosion: deflagrant or disruptive effects depending on confinement, it has a high thermal effects; availability of components: high; inertization: drowning by immersion or rather, dispersion with inert gas (CO2).
2) Oxidant: organic and inorganic oxides and peroxides (sodium peroxide and barium peroxide).
Example 2. 1: Barium peroxide and Aluminum dust. This formulation, which is widely used as a trigger for aluminothermic (metallurgical process which results in metal fusion due to heat obtainable from certain chemical reactions) may, however, be a simple way of manufacturing an explosive powder which, once activated, proceeds in accordance with the stoichiometric reaction: 3BaO2 + 2A 3BaO + Al®2OR3 The energy developed is 1885 kJ/kg. It should be noted that this type of mixture was widely used in the last war to create “incendiary bombs”. To be more precise, the ignition mechanism for an incendiary craft product consists of three parts:
– a heat source capable of starting the combustion of the greatest mass,
– a combustible material;
– oxidizing substance. Incendiary mixtures must have good chemical stability to maintain their original incendiary abilities for a long period of time under various storage conditions and safety features. The amount of heat released by an incendiary artifact varies with the nature of the materials and depends above all on the following factors:
– combustion and/or decomposition temperature;
– particle size of the incendiary and therefore surface/volume ratio of incendiary material;
– additives mixed with the combustible material to increase the rate of combustion.
An example of a widely known incendiary mixture, made with special soaps and fat acids containing Al, is Napalm, also obtained as a combination of natural or synthetic gums, polyethylene (such as poly-isobutilmethacrylate), with alkaline soaps. One of the limitations of Napalm is that at low temperature it has difficulty turning on due to the low vaporization rate of used fuels and because of their gelled form. This difficulty has been overcome by using low-density naphtha as a secondary fuel. However, the formulation is mostly the following: Sesquioxide iron (0,110 moles), Aluminum (0.257 moles), Celluloid (0.583 moles), Peroxide of Bario (0,028 moles) and Silicate of Sodium (0,022moles). The chemical reaction that takes place during the ignition of Thermite is an oxidation of Al at the expense of Fe oxide and with the contribution of air, when present. Some components contribute only partially to the incendiary effect because they have triggering or agglomerating functions. It is not possible to draw a reliable stoichiometry in advance, and the energy developed can be calculated with certainty only by laboratory tests; however, the stoichiometric reaction can be assumed as: Fe2O3+Al+ CH2+BaO2+Na2SiO3® Fe+ Al2O3+ CO2+H2O+ Na2O+ SiO2+BaO
Type of explosion: in addition to the incendiary effects, deflagrant or disruptive effects may happen depending on the confinement; availability of components: high; inertization: due to the presence of barium peroxide in contact with aluminum, dispersion with inert gas (CO2) is preferable rather than drowning by immersion.
s also possible to make other highly incendiary mixtures with effects similar to the aforementioned example. See mixture of 0.4065 moles of Potassium Chlorate, 0.25 moles of ammonium nitrate, 0,8333 magnesium moles and 0.06289 moles of copper anhydrous sulphate. One of the physical characteristics that makes this last type of mixture usable is the easy availability of materials and possible confinement, in addition to the fact, that they can be heated to 100°C and compressed to 5000 – 6000 atm without danger. For this system too, drowning presents risks that can be overcome by the use of inert gas jets.
3) Oxidant: Inorganic nitrates. The most important of this family is ammonium nitrate for which it is important providing more historical and industrial information. Ammonium Nitrate has found wide applications as a disruptive explosive ingredient, propellant and burst charges; it was first used as an explosive by Ohlsson and Norrbin in 1876. When heated, it can decompose in different ways, depending on the heating conditions. Molten ammonium nitrate first undergoes partial exothermic decomposition: NH4NO3®HNO3+NH3
Heating between 180°C and 200°C, the NH4NO3 (well dried) becomes N2O: NH4NO3®N2O+2H2O
An explosive decomposition happens with high temperature according to the reaction: 2NH4NO3®4H2O+2N2+O2.
The energy developed is 1242 kJ/kg. Since it releases oxygen, ammonium nitrate is an oxidizing explosive component that can be used in mixture with carbon or with carbon-rich aromatic nitro derives. Decomposition in the presence of carbon is accompanied by a considerable development of gases: 2NH4NO3+C 4H®2O+2N2+CO2
The energy developed is 635kJ/kg. Ammonium nitrate as a dynamite ingredient is mixed in many cases with 1% waxy materials such as petroleum jelly mixtures, resins and paraffin. The sensitivity of the explosive is so low that complete detonation of the pure product is difficult. The sensitivity of the impact is much lower than that of other ammonium salts such as picrate. It is not sensitive to friction or impact; and detonates only partially to the sand test. It should be noted that the sensitivity decreases as the charge density increases. When melted, ammonium nitrate is as sensitive as crystallized TNT. The detonation rate varies from 1100 to 3000 m/s and depends on the particles size, apparent density and triggering charge efficiency. The detonation wave of the NH4NO3 decrease in speed as it progresses, and the rate of propagation is dependent on the degree of constriction and the initial velocity of the wave. Ammonium nitrate is not toxic and there are no special precautions to handle it. It is dangerous when it burns because it is a powerful oxidant, and can increase the propagation and intensity of burning flammable material considerably. It affects all metals except stainless steel and aluminum. It is an important constituent of security explosives and is also a component of numerous other explosives. It is very easy to find and for this reason, it is unfortunately also widely used to make handicrafts. In industrial use for exploding materials, it is used to create three different types of “standard” explosives:
– explosives in which a detonating sensitizer is used to increase sensibility of nitrate detonation; – explosives in which the material used to sensitize nitrate is not detonated on its own; – “core” explosives with delayed reaction.
4) Reducing agent: all inorganic nitrates may be used on reducing substances analyzed so fa. It should be noted that inorganic nitrites also exhibit a similar behavior to nitrates. They are much less stable but can also take part in craft-type formulation. Here below there are some formulations of explosive mixtures based on Ammonium Nitrate and Potassium Nitrate:
Example 3.1: Ammonium nitrate, 0.295 moles, Aluminum, Grease as unit CH2. stoichiometric reaction can be represented as follow: (n+3/2 m)NH4NO3+ mAl + nCH2® m/2 Al2O3+(n+3/2m) N2+(2n+3m)H2O + nCO2 Type of explosion: deflagrant or disruptive effects depending on confinement; availability of components: high; possible inertization: drowning by immersion.
These considerations apply in whole or in part and also to the following examples 3.2, 3.3 and 3. 4.
Example 3.2: Ammonium nitrate, Naphthalene, Tar (as unit CH2). The stoichiometric reaction can be represented as follows: (14m n) NH4NO3 mC mC10H8-nCH2 ® N2-(n/2-4m)H2O(n-10m)CO2
Example 3.3: Ammonium nitrate (0.344 moles), Sodium nitrate , Wood sawdust (C6H10O5). The general stoichiometric approach is: NaNO3+NH4NO3+C6H10O5®N2+CO2+H2O+ Na2O
Example 3. 4: : Ammonium nitrate, Sugar. The general stoichiometric approach is: 12NH4NO3+C12H22O11®12N2+12CO2+35H2O
Example 3.5: Ammonium nitrate (0.75 moles), Anhydrous urea (0.25 moles): 3NH4NO3+ N2H4CO 2N®2+8H2O+ CO2 This reaction develops energy for 907 kJ/kg.
Potassium nitrate enters as a oxidant in the formulation of various explosive mixtures, the most important: black powder. Black powder is a mixture of KNO3, coal and sulfur of varying composition depending on use. According to Nobel and Abel, the explosion of the powder under pressure occurs according to the reaction: 10KNO3+8C+3S6CO®2+2K2CO3+3K2SO4+5N2
The energy developed is 3177 kJ/kg. Black powder burns at a rate dependent on composition, degree of incorporation and density. An increase in the concentration of KNO3 at the expenses of coal, decreases the propagation speed. The energy released by the explosion ranges from 600 to 700 kcal/kg. Type of explosion: effects which are typically more or less disruptive depending on the degree of confinement; availability of components: high; possible inertization: drowning by immersion.
Some other examples of mixtures made from potassium nitrate are given below:
Example 3.5: Potassium nitrate, sulfur and paraffin (as units CH2). The stoichiometric reaction is quite similar to the one above, with the difference that, having paraffin a considerable number of hydrogen atoms, water will also form.
Example 3.6: Potassium nitrate, sodium nitrate, Sulphur, Coal, tar of carbon fossil and potassium dichromate. The reaction products are similar to those of the previous example
5) Oxidizer: Persals other than perchlorates; Reducing: all substances listed in point 1)
Example 4.1: Potassium permanganate (0.956 moles) and Sucrose (0.094 moles). The stoichiometric reaction is:
Type of explosion: thermal, deflagrant and disruptive effects if confined; components are easy to find; possible inertization: drowning. Similar effects can be achieved by replacing the permanganates with the persulfates and perborates, both of which are easy to find.
6) Oxidizing: Chromates and chromates; Reducing agent: all substances listed in point 1).
Example 5.1: Potassium bichromate (0.5 moles), Sulfur (0.5 moles): K2Cr2O7 + S K®2O +Cr2O3+SO3
The energy developed is 255 kJ/kg. Type of explosion: deflagrant effects if confined; high component efficiency; possible inertization: drowning.
About the Author
Federico Canfarini is Deputy Inspector of the State Police and Anti-Sabotage Bomb Squad at the Ministry of the Interior (EOD/IEDD, EOD/EOR, NBCR); graduated in Industrial Chemistry at the University of Genoa, Faculty of Chemistry and Industrial Chemistry, is currently serving at the Liguria bomb squad and has obtained a Master’s degree in safety on exploding materials. An NBCR instructor and defense attorney, he attended Risk mine risk education and diplomatic security training. He attended the 2nd Cycle of the In-Depth Seminar on operational techniques and sector regulations for State Police Bomb Squads in Neptune, as well as the new qualification course at the School of Rieti in “Environmental Protection and AI2 Instrumentation”.
