Blue Line

Improvised Explosive Devices

April 29, 2013  By Tom Rataj

1119 words – MR

Improvised explosive devices

by Tom Rataj

In the wake of the Boston Marathon bombings, new light is being shed on “improvised explosive devices” (IED’s) and how even a small low-tech device, cobbled together from readily available non-military materials and equipment, can have a devastating effect.


The term “IED” dates back to the 1970s when the IRA built bombs out of agricultural fertilizer and Semtex (a commercial explosive) to further their goals, although IED’s have left a long and gruesome trail of death and destruction through many years of our history.

Most of us are probably more familiar with the term from news stories about attacks on soldiers and civilians in politically unstable places such as Iraq, Afghanistan and Pakistan.

In many of those locales, looted military munitions are assembled into a single bomb. It is not uncommon to see them triggered by radio-controlled remotes when the target vehicle passes by.

IED’s are generally very simple and designed to produce a large explosion capable of killing nearby people and destroying vehicles and buildings.

Those intended for killing and injuring people are generally packed inside a payload of some type of shrapnel, such as nails and ball-bearings, that cause serious injuries and death when propelled by the blast.

Those designed to destroy vehicles and buildings need to be much larger to create the necessary explosive energy.


An IED typically consists of some type of explosive substance, container, fuse, power source and activator device.

Many of the components can be purchased or scavenged from everyday items. The activator can be made from a wide variety of devices. For manual control, radio receivers – including cellular phones, pagers, garage door openers or radio remotes for toys – can be employed. Timed or time delayed controllers such as mechanical or electronic timers (from washing machines or lamps, for example) set off explosions automatically.

The container in which the explosives are packed is a critical design feature. The stronger it is, the larger and more powerful the explosion, even with fairly small amounts of explosive material.

Pipe-bombs, assembled from steel water pipe and caps, are typically very small but produce a massive blast because the bursting point of the pipe is very high. The pressure cooker pots used in the recent Boston Marathon bombings were also quite effective because they are designed to contain high pressures.

Additional components added to IED’s can increase their collateral damage. In addition to the usual shrapnel, liquid chlorine and other chemical, biological and incendiary materials are used. Liquid chlorine creates a cloud of deadly chlorine vapour in the blast area. Chemical or biological agents can contaminate the area and victims, while incendiary materials will add a fuelled fire to the aftermath.

Larger IEDs used in car or truck bombs can deliver massive amounts of explosive power to a target site, as seen in the Oklahoma City bombing in 1995 and various other locales.

{Pressure cookers}

Boston introduced pressure cooker bombs into the popular consciousness, although they have been used extensively around the world for many years. They are a simple and effective type of IED because all the materials are readily available and can be sourced without arousing suspicion. A pressure cooker pot, typically found in kitchens, is filled with an explosive charge and surrounded by shrapnel, then completed with a fuse and trigger mechanism. The bomb can be triggered remotely by radio controlled devices or by a timer.

Seven pressure cooker bombs exploded on suburban railway cars in Mumbai, India in July 2006 over an 11-minute period, killing 209 people and injuring over 700. The Islamist Lashkar-e-Qahhar group claimed responsibility, saying it was in retaliation for the Indian government’s alleged repression of Muslim minorities.

The two Boston Marathon bombs were also apparently fashioned from a home-grade pressure-cooker pot, nails and ball-bearings for shrapnel, gun-powder extracted from fireworks and a garage-door opener remote control as the trigger mechanism. The two brothers accused were allegedly motivated by extremist religious views.

{Fertiliser bombs}

Ammonium-nitrate agricultural fertilizer is at the core of this increasingly common IED. In recent years it was most famously used in the April 1995 Oklahoma City bombing.

Timothy McVeigh and Terry Nicols used an ammonium-nitrate truck-bomb to destroy the Alfred P. Murray Federal Building in downtown Oklahoma City. The explosion destroyed a third of the building and substantially damaged another 324 buildings within a 16-block radius, killing 168 people and injuring more than 680.

The bomb consisted of about 2,200 kg (4,800 lbs) of ammonium-nitrate fertilizer, nitromethane (commonly used in Top Fuel drag racing cars), stolen Tovex (an industrial explosive), electric blasting caps, diesel fuel, a timer and an assortment of wiring and tubing to connect all the components together into one bomb. The entire device cost less than $5,000 to construct and deliver to the site.

Closer to home, “The Toronto 18” case made national and international headlines in 2006. A group of radical Islamists were arrested during a series of raids prior to implementing their plan. The investigation showed that they intended to assemble and detonate a number of fertilizer bombs in attacks on the Canadian Parliament, CSIS headquarters and other public targets.

{Blast pressure}

The shockwave created by an explosion is often underestimated. Even if the bomb or other explosive material, (such as the recent fertilizer plant explosion in Texas), is not designed or intended to injure, the shockwave is often enough to kill or seriously injure people and damage or destroy buildings, often at a substantial distance from the epicentre.

The primary cause of injuries from explosions is the “overpressure” the shockwave creates, which consists of atmospheric pressures substantially higher than normal. They can cause many serious internal injuries.

For persons closest to an explosion, the most common injuries are to the ears, lungs and hollow organs such as in the gastrointestinal tract.

If the victim does not receive external injuries from shrapnel or other objects propelled by the explosion, or from being propelled into or against objects, they may exhibit no apparent symptoms (other than hearing loss) until hours or days later.

Internal bleeding often manifests itself many hours, days or even months after the blast. Hidden brain damage and “blast-induced neurotrauma” (BINT) can cause many long term health problems.

{Threats to police}

In many politically unstable parts of the world, police are often targets of radical groups because they are the most visible representatives of the government.

While the situation in Canada is substantially different than elsewhere in the world, it is not inconceivable that we could also be targeted by radical groups or individuals.

IED survivability is largely a factor of distance from the blast, so creating very large perimeters while investigating suspected IED’s in very important.

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