The first large-scale use of IEDs was probably during World War II and ever since IEDs have been used both as an unconventional warfare in military theatres of operation such as in Iraq and Afghanistan and in terrorist attacks such as the Bali (2002), Madrid (2004) or London bombings (2005).
IEDs can be manufactured from military and commercially based explosives or home-made explosives and often a combination of these are used in terrorist attacks. The bomb factory may be in an apartment in a large city such as those used in the London Underground attacks and consequently very difficult to both discover and localise.
The Bali bombs, 2002, were manufactured in a two-story house a few kilometres away from the terrorist attacks resulting in hundreds of dead and injured people. The bomb factory had not been disturbed since the bomb makers departed and forensic experts could make a vast amount of analyses. Both of the substances used in the Bali bombs are non-volatile and unrealistic to find in air, however, it is likely that these can be detected as traces in the vicinity of bomb factories or in the waste water pipes originating from these facilities.
The terrorist attack executed on the London Underground July 2005 is a horrible example of the result from the manufacture of home-made explosives. The manufacturing of the bombs for the London Underground were performed in the neighbourhood of Leeds. In contrast to the bombs used on July 7 resulting in many victims and injured people, the bombs used on July 21 all failed giving much material for forensic analyses. The bombs were based on a home-made peroxide system where ordinary commercially available hydrogen peroxide was bought.
The dispersion of explosives and precursors to the surrounding air is a function of parameters such as weather conditions and city architecture.
In March of 2004 in Madrid, ten bombs against the commuter train system exploded due to a coordinated terrorist attack resulting in hundreds of killed and injured people. Shortly after the attacks the police identified an apartment in Leganés in south of Madrid as the likely bomb factory. The suspected people trapped in the apartment set-off their explosives resulting in killing themselves, nevertheless, investigators later found out that the explosives used by the suspects were of the same type as those ten bombs used on 11 March. The bombs were found to be made of Dynamite probably bought from a retired miner who still had access to blasting equipment. Also for this terror attack an apartment was used as an IED manufacturing facility in an area with a large number of inhabitants.
An increasing threat to the European cities is IEDs made from firework materials. The United Kingdom has a specific task force set up to deal with this issue.
It is evident that there exists an urgent need for new tools in the extensive work of preventing future terrorist attacks.
FOI, Swedish Defence Research Agency