Arson occurs when someone intentionally causes something to burn. This is usually done by setting a fire or using a device to set a fire, though many laws also categorize bombings as arson. An arson attack occurs when fire or a bomb is used to intentionally harm someone. This type of arson is usually considered to be aggravated arson. Fire and police departments use a number of methods to determine the cause of fires, and whether they were the result of an arson attack.
Arson fires can be set in a number of ways, including using an accelerant, which is usually a very flammable liquid or gas. Gasoline is one of the most common accelerants used during an arson attack. Other common liquid accelerants include kerosene, oil, solvents, and alcohol. These types of accelerants are often quite harmless on their own. When there is a spark or flame put to them, however, a dangerous fire can result.
Arsonists typically use an igniter to start a fire. Often, these can be something simple, such as matches, a lighter, or lit rags or paper tossed onto an accelerant. Sometimes though, arsonists use shortened candles as igniters, which take time to burn down. Wiring in devices such as light switches and electrical cords can also be tampered with to cause sparks that will ignite an accelerant or its fumes.
Although accelerants and igniters make it much easier for a fire to be started by an arsonist, they also make it easier for law enforcement officials to determine that the fire was an arson attack. Most accelerants have a distinct odor that investigators can often smell. Catalytic combustion detectors, as well as specially trained dogs, can also detect the presence of some accelerant fumes. Many accelerants also leave a residue that can stain surfaces like floors and walls. Traces of an accelerant used to start a fire also may be found be on an arsonist's clothing or hands.
One of the most famous arson attacks was in the United States on 11 September 2001, when terrorists hijacked four airplanes. Two were deliberately crashed into the World Trade Center in New York City, and one was crashed into the Pentagon in Washington, D.C.. After the crew and passengers attempted to reclaim the fourth plane, it crashed outside a small town in rural Pennsylvania.
As a result of these planes being hijacked, about 3,000 people were killed. The majority of the deaths were thought to be caused by the fires and smoke caused by the impact. Also, hundreds of fire fighters died while attempting to control the fires and rescue civilians.