Where it has been determined that such a building could be the subject of a terrorist-based threat from explosives, building operators normally take every conceivable measure to mitigate such an incident. This can range from simple baggage checks through to the use of x-ray technologies, normally accompanied by the use of trace explosives detection instruments such as those offered by Bruker. Visitors to the building can be chosen at random or may be chosen based on both gathered intelligence, which itself can be based on behaviour monitoring techniques, and/or the discovery of the presence of suspicious materials in hand baggage and boxes that they wish to take into the building. Threats from explosives devices can be largely mitigated by the use of trace explosives detectors. Individuals are chosen based on either security protocols or specific concerns and their personal property, or the packages that accompany them, are checked with the trace explosives detector.