IMPROVISED EXPLOSIVE DEVICES
Improvised explosive devices (pipe bomb, car bomb, shoe bomb) are designed to conceal and deliver quantities of explosives to a target. Explosives have been the most widely used terrorist devices against transit systems for more than 80 years. Explosives by themselves may be less catastrophic than chemical, biological or radiological weapons. They are also easier to build or acquire, plant and detonate than more sophisticated weapons, and they accomplish the terrorist's primary goal: to cause death and damage and instill fear to terrorize society.
CHEMICAL AGENTS
Chemical agents are used to poison victims. Toxic and incapacitating chemical substances are intended to kill, seriously injure or incapacitate humans through physiological effects. These agents, if properly dispersed, can cause immediate or short-term mass casualties and fatalities. Non-fatal agents such as pepper spray can still cause panic and hysteria in a crowd because of their inherent irritant properties.
BIOLOGICAL AGENTS
Biological agents are germs that will cause disease in people. Some of these are deadly to animals as well, though they are not the primary targets. Unlike chemical agents, biological agents may not produce visible symptoms in victims for hours or days after exposure.
RADIOLOGICAL AGENTS
Radiological materials can pose both an acute and long-term hazard to humans. In many ways, they behave like some chemical agents in that they cause cell damage. A major difference is that the radiological agents do not necessarily have to be inhaled or come in contact with the skin to do damage. Some types of radiation, like X-rays, can penetrate several layers of protective material
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