Weapons of mass destruction utilized by terrorists fall into one of five different types of substances used for that purpose: nuclear weapons, incendiary devices, chemical weapons, explosives and biological weapons. Nuclear weapons work in some cases by a process known as nuclear fission, where the nucleus of an atom splits into two fragments, releasing huge amounts of destructive energy. Other nuclear weapons work by nuclear fusion, in which two atoms’ nuclei collide at high speeds to create a single, entirely new nucleus.
Another type of substance used to terrorists to inflict harm on others is incendiary devices. These aim to blow up and sometimes to ignite fires across a wide area of space which would burn, if possible, at a very high temperature. Probably the best known kind is a Molotov cocktail, which can be made cheaply and more or less easily. Sometimes they work by combustion – the reaction of oxygen and some kind of fuel at very high temperatures – and other times by detonation, when the breakdown of molecules creates an explosion without any need for oxygen to make it happen . They make use of a variety of substances. Napalm, for instance, conventionally been used in incendiary devices. Other flammable metals like aluminum or titanium are also typical because they burn at very high temperatures.
Chemical weapons first came into use during World War I, when armies on both sides of the conflict used chlorine and phosgene to suffocate their enemies and mustard gas to inflict burns on their skin. Later, gases were developed solely for military purposes. Nazi scientists in 1938 developed sarin, a colorless, odorless gas which kills by being inhaled or absorbed through the skin and quickly paralyzing the victim’s respiratory system. It has most recently been used by the Syrian government, itself a state sponsor of terror, in war launched by its government against its own citizens. “Dirty bombs” could sometimes be considered a kind of chemical weapon, although they sometimes incorporate elements which are common to nuclear weapons as well. They combine more conventional explosives with radioactive material which can poison populations with radiation. For that reason, they are often the most feared sort of nuclear weapon in the case of terrorism, because terrorists would find it a lot easier to get their hands on them.
Explosives, especially improvised explosive devices, remain the terrorist weapon of choice because of their relative ease of construction, availability, and destructive capacity. They need a fuel and an oxidizer in order to detonate. Commonly available materials like fertilizer, gunpowder, and hydrogen peroxide are often used for these ends. They may also include materials which would turn into shrapnel upon exploding, like nails, glass or metal fragments. The Department of Homeland Security’s restriction on liquids on airplanes is motivated by concern over the possibility of someone creating explosives from widely available liquids brought in separately and mixed on the plane or in the airport.
Biological weapons – the “B” in the five BNICE categories of substances – are defined by the Department of Homeland Security as pathogens (disease-causing agents) or biotoxins (poisonous substances produced by a living organism) which are released intentionally to harm humans, plants or animals. Attacks against people can cause sickness, death, fear, economic losses and societal disruptions, while an attack on plants and animals would probably be more targeted to cause economic damage and destabilizing fear among people. The DHS says there are two main kinds of biological weapons: transmissible agents like smallpox or Ebola which spread from person to person or, in the case of diseases like foot and mouth disease, from animal to animal; and non-contagious agents like anthrax which are potentially very harmful to