Explosives have ripped apart people and property since the gun powder was first used in China some 870 years ago. Though the primary purpose of explosives for centuries was as weapons of war, their peacetime potential was eventually realized. Today explosives are vital to civilian industry and technology—as well as in the military.
Modern society cannot exist without explosives, but the injuries, death, and destruction they cause are evident to anyone who reads news reports.
Many of these diverse explosion dangers do not result from the intentional use of explosives, but rather from the unintentional ignition of explosive substances.
Explosions throughoutt history
Here are a few examples of explosions that have occurred in the last decades:
- A gas plant explosion in a suburb of Mexico City kills 452 people, and many more are injured and homeless.
- At least 508 people, but probably more than 700, including 300 children, perish in the Brazilian shantytown of Cubatao when a leaking gasoline pipeline explodes.
- A huge and mysterious blast at the Society naval supply depot at Severomorsk reportedly wipes out more than 200 people and destroys large stocks of ammunition.
- An explosion apparently caused by methane gas in a coal mine in Commodore, Pennsylvania, injures ten miners. Three others are missing and presumed dead.
- Airborne flour dust ignites at a milling company in Clifton, New Jersey, injuring three workers and blowing out walls at the plant.
- An explosion rocks an oil refinery in Rotneoville, Illinois, killing 17 people, injuring 23 others, and knocking out electrical power to 10,000 homes. Windows are shattered for miles around. Fire rages out of control at the refinery.
- The explosion of an ammonia tank in the refrigeration system at a meatpacking plant in Vernon, California, unleashes a huge ammonia cloud, injuring 60 people and driving dozens of employees into the streets for fresh air.
- A Los Angeles, California, firefighter dies from smoke inhalation when his air supply runs out in a burning restaurant following a “back-draft” explosion of smoke particles.
Bombings and Disasters—Additionally, scores of people are killed, hundreds are injured, and tens of millions in property damage result annually from bombings and other explosives incidents reported to the Bureau of Alcohol, Tobacco and Firearms (ATF)
In the most recent year for which statistics are available, 715 explosive incidents were reported. There have also been numerous large-scale explosion disasters in the past, in the U.S.:
- A ship with a cargo of ammonium nitrate fertilizer catches fire and explodes while docked in Texas City, Texas, on April 16, 1947. This and subsequent explosions and fires, kill 561 people.
- Another ship explosion at Port Chicago, California, on July 18, 1944, kills 322 people.
- A New London, Texas, school explosion on March 18, 1937, kills 294.
- A munitions plant explosion in Eddy-stone, Pennsylvania, on April 10, 1917, kills 133.
- Another 130 people die in a Cleve-land, Ohio, gas tank explosion on Oct. 20, 1944.
- And a coal mine explosion in Monongha, West Virginia, on Dec. 6, 1907, kills 361.
- These are some of the most lethal explosion disasters in this century in the U.S.
It could be impossible to protect oneself and family against all explosion dangers, many of which are not recognized until it is too late. But for preppers and survivalists, a fundamental knowledge of explosives and some of the hazards they represent can aid in efforts to secure a measure of protection.
A brief history lesson regarding explosives
In addition to their many applications in warfare, explosives are employed in agriculture, road building, and other construction, and in mining and manufacturing, to cite just a few peaceful uses. Pyrotechnics, or fireworks, is one of the major recreational uses of explosives. Today, science is discovering important uses for explosives in space technology.
The origin of gunpowder (black powder), the first true explosive, is obscure, but the Chinese probably were aware of the properties of saltpeter (potassium nitrate), one of the constituents of gunpowder, as early as 207 B.C., though its use was not developed beyond fireworks until about 1150 A.D.
Knowledge of the effects of gunpowder soon spread to the Arab world and Europe. The first recorded western experimenter to establish the formula for gunpowder was an English monk named Roger Bacon, a scholar, mathematician, and scientist.
Its first use as a propellant in Europe occurred about 1320. The Arabs may have used gunpowder about the same time. English troops used cannon against the French in 1346.
The formula for gunpowder has changed since, but its basic constituents—potassium nitrate, carbon, and sulfur—have not. It is now used only as a propellant in replica firearms by shooters who enjoy weaponry of times past. It burns very quickly, about 400 meters per second. Its residue fouls rifle and pistol bores and fosters destructive corrosion.
On the other hand, it burns too slowly to produce the shattering effect of modern “high” explosives. Dangers associated with uses of black powder will be discussed farther along in this article.
Scientists and inventors tinkered with other forms of explosives for centuries, leading to some notable developments in the field, but it was not until the 1800s when the Swede, Immanuel Nobel, and his sons, most importantly Alfred, began successful commercial production of more powerful explosives.
Expanding on the ideas of other inventors, the family started to produce “Nobel’s blasting oil,” a version of the highly volatile glycerin trinitrate.
This substance proved highly unstable, however. A tragic accident occurred in 1864 in which the Nobel works blew up, killing one of Alfred Nobel’s brothers and maiming his father. Alfred developed a more stable yet powerful, explosive, which he called dynamite, after the Greek word for power, and saw it enter world markets in 1867. Dynamite revolutionized the industry and led to the development of other types of high explosives and “smokeless” gun powders.
Perhaps Alfred Nobel’s greatest contribution to chemistry was his discovery that the shock-spreading wave of a high explosive detonation is significantly different from the flame-spreading of ordinary black powder.
When a black powder explosive is set off, it undergoes rapid decomposition and releases large quantities of gas and heat. The explosion is a fast combustion or burning, the burning spreading layer by layer through the material exploded at a comparatively slow velocity of up to 400 meters (1.312 feet) per second. Although its rate increases with increasing pressure, the burning can be controlled. This reaction is often called deflagration.
The term deflagration is used to describe the burning of so-called low explosives such as black powder. In the far more powerful high explosives, the burning reaction is referred to as a detonation. It is an extremely rapid burning which produces a supersonic (faster than 741 mph) shock or detonating wave, in an explosive material.
The detonation velocity is a characteristic of the explosive substance itself and is unchanged by changes in pressure. It is usually between 2,000 and 9.000 meters (6,500 and 29,500 feet) per second. The detonation wave produces very high pressure, about 650 tons per square inch, and this exerts a severe shattering effect on anything in its path.
The gases formed travel in the same direction as the detonating wave, so a low-pressure region is created behind it. Once the detonation has been started, it cannot be stopped.
The fundamental properties of explosives are the velocity of burning or detonation, the explosion temperature, sensitivity, and power. The more sensitive explosives are used in modern “explosive trains” to set of intermediary charges (thee with moderate sensitivity), which in turn initiate reactions in the main charges, which are least sensitive but have greater overall blasting power.
The use of gunpowder (black powder) as an explosive declined in the 19th Century. It was replaced by three main types of composition: those explosives based on unstable molecules, such as the fulminates and azides, ammonium nitrate, and the organic esters nitrocellulose, nitroglycerine and PETN; and the nitro-compounds, a large group which includes picric acid, TNT, tetryl, and RDX.
Explosions may occur with a resulting fire, without a resulting fire, or because of a fire. But explosions and fires are often associated with each other. Explosions may be divided into two categories: high yield and low yield.
The difference between the two is the rate at which energy is released. Those explosions with higher energy release rates will be high yield and vice versa. The distinction between these two types of explosions is somewhat arbitrary, and there is some overlap.
One important difference between the two types is the resulting damage effects.
High-yield explosions tend to produce shattering of nearby materials and cratering of floors and foundations. This is generally accompanied by high-velocity projectiles and/or fragmentation.
Low-yield explosions do not normally produce this shattering. Their action is more of a pushing or shoving of nearby materials. The destructive effects of the two types of explosions can be similar, particularly when equivalent amounts of energy release are involved, though the damage effects in the immediate vicinity of the explosions may differ.
For example, detonating dynamite in a room or building might result in a hole in the floor, shattering of nearby furniture and blowing out of nearby windows, either from a pressure wave or projectiles. The chance of a resulting fire is low. But vaporization of a sufficient amount of gasoline with subsequent ignition (low-yield explosion) would produce no hole in the floor, no shattering of nearby furniture, but could result in ignition of combustible furniture and drapes, and blowing out of windows and walls.
In the case of the dynamite explosion, a fire, if it resulted, would probably be from secondary ignition sources, such as dislodged electrical circuits combining with a fuel source, such as a broken gas pipe. In the second example, there is a distinct possibility that the explosion itself could produce a fire, particularly when easily ignitable materials such as furniture and draperies are present.
High-yield explosions generally include commercial explosives, such as TNT, dynamite, nitroglycerin and ammonium nitrate, and black and smokeless powders when confined.
Low-yield explosions generally include explosions or ruptures of containers of flammable liquids and gases, combustible dust, pressure vessels, and black and smokeless powders when unconfined. Low-yield explosions can also include back-draft explosions in which concentrations of smoke particles ignite during a fire.
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Flammable liquids and gases can frequently produce explosions. They possess four interdependent properties that determine whether an explosion can take place. These are flashpoints, explosive limits, ignition temperature, and vapor density.
Flammable liquids do not burn or explode themselves. It is the vapor rising from the liquid surface, which, when mixed with air, forms the explosive mixture. The temperature at which a liquid gives off sufficient vapors to form an ignitable mixture with air is called the liquid’s flashpoint.
The range of mixture of air with a flammable gas or vapor from a liquid that will explode (that is, burn rapidly) is relatively narrow for most gases and vapors.
Below a certain percentage, by volume, a mixture of flammable gas or vapor with air will be too lean (lacking sufficient fuel) to explode. Above a certain percentage, the mixture will be too rich to explode. The lower percentage and the upper percentage are called the explosive limits.
For gasoline, for example, the limits are about 1.3 percent to 6.0 percent. For natural gas or methane, the limits are 5.0 to 15.0 percent. These limits apply only at normal temperature and atmospheric pressure.
Before a flammable gas or vapor/air mixture can ignite, the mixture or at least a small portion of it must be raised in temperature. The temperature necessary to produce the ignition is called the ignition temperature. While the mixture may occupy a large volume, if the total mixture lies within the explosive limits, a very small spark occurring anywhere within the mixture’s volume can produce ignition of the total mixture.
The vapor density of a flammable vapor or gas is usually measured relative to that of air. A substance with a vapor density of 2, for example, is twice as heavy as air. The vapor density and subsequent behavior of the vapor or gas discharged into the air can be extremely important. The vapors of a liquid which are heavier than air tend to sink to the lowest possible level. They can flow out over considerable distances while forming concentrations within the explosive limits.
On the other hand, those that are lighter than air tend to rise and thus remove themselves from possible ignition sources at lower levels.
So, leaking propane gas is more likely to cause an explosion in the basement of a house, where ignition sources are low than leaking natural gas. If natural gas is confined, however, as in a basement from which it cannot escape, and if the leak continues, then ultimately, the basement will be filled from the ceiling to the floor with gas. If there is an ignition source near the floor, the resulting explosion may be more violent, due to more gas being present.
Combustible materials in solid form, when ignited, burn relatively slowly, releasing energy gradually. The rate of burning and ease of ignition are generally dependent on the ratio of the surface area to the volume of the material exposed to air.
The greater the volume to the surface area, the more difficult it is to ignite, and the slower it burns. As the combustible material is reduced in size, the easier it is to ignite, and the more readily it burns. If the combustible material is reduced to a powder or dust and is intimately mixed with air through mechanical agitation or through blowing, the dust cloud, if ignited, can burn so rapidly an explosion is produced.
Combustible dusts include agricultural dust, coal dust, chemical dust, metal dust, rubber dust, pesticide dust, and dust from plastics manufacturing. There are hundreds of dust capable of producing dust explosions, but agricultural dust has been responsible for the more spectacular and destructive explosions.
Combustible dust, like flammable vapors and gases, have finite explosive limits. For most combustible dust, the lower explosive limit is around 0.02 ounces suspended in 1 cubic foot of air. The upper explosive limit is less well defined.
As with flammable vapors and gases, combustible dust must contact an ignition source to explode. This ignition can be from a small spark, open flame, or hot surface. Many combustible dusts can be ignited by hot surfaces in the range of 750 to 1.100 degrees Fahrenheit (399 to 593 degrees Celsius).
Dust explosions, while not as common as flammable vapor/gas explosions, tend to be a hazard in certain types of structures, including grain elevators, flour mills, candy factories, paint manufacturing operations, and metal powder plants.
Dust explosions produce damage effects similar to flammable gas/vapor explosions. Walls can be dislodged or blown out, and buildings may collapse. Combustible dust explosions, unlike flammable gas/ vapor explosions, however, can produce a chain of explosions.
The first explosion may be rather small in intensity, but it may raise additional clouds of dust, resulting in another, more severe explosion, which in turn could lead to yet a bigger explosion, and so on.
Fires involving small arms ammunition with smokeless powder are not unusual. They can occur in a gun store or a sporting goods store, or in a home where the owner has stored ammunition. But these fires are not as dangerous, from an explosion standpoint, as some people believe they may be.
Actually not entirely smokeless—won’t detonate when exposed to heat. In a fire, cartridges may explode individually, not altogether. When the cartridge explodes, its bullet may move a few inches at most, and its brass case may fly a bit farther, as an uncontained explosion permits gases to escape in all directions.
One can still be injured or killed when close to an exploding cartridge, however, so keep clear of a fire with exploding ammunition. It is not necessary to evacuate to a great distance away. A solid wooden barrier or mound of earth will provide adequate protection. Caution: this does not apply to burning cartridges inside firearms. A loaded gun’s bullet exits the barrel with velocity identical to that when it is discharged by a firing pin.
Black powder, on the contrary, is extremely hazardous when exposed to heat. Many experts consider black powder to be among the most dangerous of the more commonly used explosives. While black powder burns at a slower rate than high explosives, it still burns rapidly when ignited, and in dry form, it is easily ignited. The ignition temperature of black powder is so low that the slightest spark will set it off at normal temperatures.
The static electricity from a charged human body has been known to explode it. A sufficient wetting of black powder with water will destroy its ability to burn or explode. When storing it, make sure there is plenty of water available nearby in case it is needed.
Black powder is seldom used today as a propellant except by sportsmen. However, it is still used in some primers, safety fuses, airplane flares, some hand grenades, practice bombs, blank cartridges, fireworks, and signals. When transporting, storing, or handling black powder, make sure it is kept cool and away from electric ignition sources.
While explosives vary widely in strength, each possesses different characteristics, and each will react according to several factors affecting it.
One of these factors or variables is the degree of pressure or confinement. A second is the intensity of heat needed to ignite or detonate the explosive. A third variable is the degree of shock sensitivity. These variables tend to be interrelated.
Shock sensitivity of a particular explosive can be affected by the amount of heat it absorbs and the pressure on it.
Most high explosives require the shock of a more sensitive explosive to set them off. But at a high enough temperature, every explosive will explode. Every explosive can also explode after prolonged exposure to somewhat lower temperatures. Keeping them as cool as possible when storing, transporting, or handling them, reduces the probability of an explosion.
A commonly misunderstood explosive, the cause of many injury accidents, is the blasting cap. Caps are used widely to set off high explosive charges in mining and construction. They are pencil diameter metallic casings, available in varying explosive intensities, and in configurations for fuse or electrical detonation. Many are pressure- or impact-sensitive.
The Institute of Makers of Explosives says, “More than 100 million blasting caps are used every year in the U.S. for construction and building, mining and quarrying . . . A few of the 100 million caps .. . become lost . . . or stolen. And when they get into the wrong hands, the results can be tragic. When handled improperly, blasting caps can cause serious injury .. . even death. They can rip your face, blow off your fingers, put out your eyes, and make you deaf. So, it’ you find one, don’t touch. You may end up with nothing to touch with . .”
Explosives are subject to a number of federal, state, and local government regulations when transported by rail or on public roads by common carriers. These are too numerous to cite here, but a brief mention of some regulations is in order.
The Bureau of Explosives of the Association of American Railroads has established classes of explosives, based on their relative dangers:
- Class A explosives will either detonate or, as in the case of black powder, present a maximum fire and/or explosion hazard. Class A explosives are subdivided into nine groups according to form, chemical composition, and ease of detonation. The class includes black and smokeless powders, dynamite, nitroglycerin, TNT, amatol, picric acid, and blasting caps. Also included are cannon and rocket ammunition, grenades, bombs, mines, and torpedoes.
- Class B explosives function, in general, by rapid combustion rather than detonation. Once initiated in these materials, a fire is impossible to extinguish until they are consumed. The hazard presented here is primarily one of fire. Included in this class are special fireworks, some types of ammunition, and Clash cartridges as well as most smokeless powder propellants.
- Class C explosives may contain restricted amounts of Class A or Class B explosives. This class of explosives is considered to present a minimal hazard. Examples are rifle and pistol ammunition, explosive rivets, common fireworks, fuses, smoke signals, and flares.
If an accident involving these classes of explosives occurs nearby, make sure authorities are notified immediately. If possible, care should be taken to prevent the spread of any fire, or to prevent damage from further explosions.
If a fire has started near these explosives, make every effort, without endangering lives, to extinguish the fire and remove undamaged explosives to a safer location
The recommended evacuation distances for accidents involving these explosives are:
- Class A explosives, 1 mile,
- Class B explosives, ½ mile,
- Class C explosives, 1,500 feet.
There are also forbidden explosives that cannot be shipped by a common carrier, by rail freight, rail express, highway, or water. These include explosive compositions that ignite spontaneously or undergo marked decomposition when subjected for 48 hours or less to a temperature of 167 degrees F (75 degrees C); explosives containing ammonium salt and a chlorate; liquid nitroglycerin, diethylene glycol dinitrate; and leaking or damaged packaged explosives.
The U.S. Department of Transportation requires that placards identifying the class of explosives be placed on vehicles carrying any quantity of them, except Class C explosives, which do not require placarding.
In discussing explosion dangers, it is necessary to mention some common household perils.
Avoid using flammable liquids such as gasoline, acetone, and butane for anything other than their intended purposes. Many of these materials begin evaporating at room temperature, and the vapors can easily ignite and explode. Read and follow label instructions and warnings.
Aerosol cans, such as hair spray and insect repellent, are potential bombs. Many of these sprays are easily ignitable and explosive. Never use them near a heat source and store them in a cool area according to the manufacturer’s directions. Do not puncture or handle them violently.
Maintain water heaters, gas boilers, or other equipment with steam pressure safety values in good working condition. A faulty or plugged pressure release valve could lead to a blast that kills or maims. Never block off these valves as a few ignorant persons have to keep them from dripping water: they were meant to do just that.
Some dry chemicals can combine with other substances found in the home to produce toxic and volatile compounds. Again, follow label instructions and warnings and keep children away from these substances.
As stated earlier, potential explosions are almost everywhere. Some explosions, criminal bombings, and oil refinery disasters, for example, cannot always be anticipated. However, awareness of the potential for an explosion can help the individual to anticipate and prepare.
Those who live close to manufacturing plants, chemical industry complexes, truck terminals, and other repositories of explosive substances would do well to study what is being manufactured/trans-ported/stored nearby and what steps have been taken by the owners to avoid explosions and/or respond to an explosion should it occur.
If one’s residence is in the vicinity of such industrial developments, where the odds favor an explosion/fire in the future, it would be wise to develop a family contingency plan in the event of such a disaster.
Make sure you have the necessary first aid equipment, protective shielding, an escape/evacuation route, or other items to survive the effects of an explosion, be it a small one in the home or a massive one at a local industrial facility.
Learn which kinds of explosives are in the specific locale, learn the explosive potential of such substances, and then learn how to deal with an explosion and its aftermath, should such an event occur.
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