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McHenry County Department of Health
Emergency Response Program
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Working to protect the health and safety of McHenry County Residents
by planning for and responding to public health emergencies
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What is a Bomb/Explosive Device? A bomb is an explosive device designed to cause random destruction when set off; an explosive device is defined as any materials capable of violent decomposition. After a bomb or explosion is detonated, energy is released rapidly, as a powerful, destructive shock wave. Bombs are the most frequent weapons currently used by terrorists and account for approximately 70% of all terrorist events. Although the purpose behind many bombs is to cause harm and destruction through an explosion, bombs can also be used to disperse chemical, biological, incendiary and nuclear agents. Bombing incidents can involve a wide variety of materials from small pipe bombs to large vehicle bombs and may target a fixed object/place or a group of people. The incident may be a single event or may involve secondary devices, booby traps or suicide bombers. The type of bomb involved may be an improvised (e.g. homemade) or a commercially manufactured explosive. Because a bomb may be equipped with various switches or controls that can be activated by light, pressure, movement, or radio transmission, untrained personnel should never attempt to defuse an unexploded device. Any bombing or suspicious fire may be the result of terrorist involvement, especially combined with location or occupancy factors (e.g. historic/symbolic location, public buildings, controversial businesses or critical infrastructure systems). What Happens in an Explosion? Explosions are the result of abrupt and violent release of gas during the decomposition of explosive substances. This release is followed by high temperature, strong shock and loud noise. Explosives, when detonated, create three primary effects – blast pressure, fragmentation and thermal effects. There are two different phases of blast pressure. Positive blast pressure (overpressure) moves rapidly away from the explosion center (ground zero) due to the expansion caused by the release of energy. After the positive pressure phase, a vacuum is created at the explosion site. This creates a negative pressure that moves toward the original center of the detonation at hurricane speed. It is less sudden, but lasts approximately three times as long as the positive pressure wave. Fragmentation occurs when the explosive device propels fragments at high speed for long distances. This often accounts for many of injuries or casualties. Thermal effects are sometimes referred to as the incendiary effects. Heat produced by the detonation of either high or low explosives varies according to the ingredient materials. The thermal effect is visible in the bright flash or fire ball temporarily produced by an explosion. What is an Incendiary Device? An incendiary device is any mechanical, electrical or chemical weapon designed to intentionally create a fire in order to burn other materials or structures. Fire is a flexible tool that is capable of causing property damage, loss of life and producing panic. It continues to spread and do damage until all available fuel is consumed or the fire is extinguished. Incendiaries can be teamed with bombs/explosives, but can be used separately as well. Statistics show that approximately 20-25% of all bombing incidents in the United States used incendiary devices. Incendiary devices may be simple or complex and come in all shapes and sizes. The type of device is limited only by the terrorist's imagination and ingenuity. An incendiary device can be a simple match applied to a piece of paper, or a matchbook-and-cigarette arrangement, or a complicated self-igniting chemical device. Normally, an incendiary device is a material or mixture of materials designed to produce enough heat and flame to cause combustible material to burn once it reaches its ignition temperature. Incendiary devices are classified by triggering and delivery methods. Triggering refers to the way that the incendiary reaction is initiated. Delivery methods can include hand-thrown, stationary, planted or self-propelled. Only specially trained personnel should handle incendiary devices discovered prior to ignition. Handling of such devices by inexperienced individuals can result in ignition and possible injury or death. In addition, proper handling is critical for crime scene preservation. (Source: U.S. Department of Justice, Ready.gov - U.S. Department of Homeland Security) For More Information, Please Visit: Terrorism
McHenry County Online ~ MCDH Online  McHenry County Department of Health 2200 N Seminary Ave, Annex A Woodstock, Illinois 60098
Telephone (815) 334-4510
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