Swanson, Charles R., Chamelin, Neil C., and Territo, Leonard. Fire Setting
and Related Mechanisms. Criminal Investigations, Sixth Edition. pp. 666
Abstract: Chapter 20 of Criminal Investigations discusses the
methods of arson. An incendiary device requires an ignition device and a
"plant" to feed the initial flame. Some arsonists also use trailers
to spread the fire throughout the building and the more elaborate arsonist
will use a timing device.
There are many different ignition devices used for arson. The traditional
match is not usually used by arsonists because of its immediacy. Most firesetters
want a delay so they will attach the match to a timed device. A commonly
used timer is a cigarette. The cigarette will continue to burn if laying
on its side and can easily ignite a match located towards the middle of
Candles are another ignition source used by arsonists for years. The
book contains a table listing the time it takes different compositions and
sizes of candles to burn. When used as incendiary devices, candles are often
placed in containers of highly combustible materials and placed near an
accelerant. Candles are often detectable because they leave deposits of
Chemicals are another popular ignition device. A common method of chemical
ignition requires acid to mix with a combination of chemicals. The acid
is usually stored in a container that it will slowly eat its way through.
Most fires started by chemicals will have signs pointing to their cause.
Usually, debris will contain chemical residue and have a distinct odor.
Gas is a less common ignition device, but it is simple to use in a residential
house. Gas rises to the ceiling and will escape in a well-ventilated room.
If the room is sealed, gas cannot escape and will accumulate. When the gas
reaches the pilot light on a stove, it will ignite and explode.
Electrical systems have also been used as ignition devices. Circuits
may be deliberately overloaded causing them to heat. Sometimes an accelerant
is placed in the switch box, which will explode when the overload occurs.
Some arsonists will replace normal wiring with lighter wiring causing the
wire to overheat without blowing any fuses. Investigators will usually discover
physical evidence implicating wiring as the cause of a fire.
Mechanical devices can also be used as ignition sources, although they
are not common. Clocks were once a popular device for arsonists. The hammer
for the alarm would be rigged to hit a glass tube containing a flammable
liquid. This tube would in turn break another small tube containing another
liquid. These combined liquids would ignite the fire. This method was abandoned
because many of the machines used would not burn, leaving evidence at the