Once you've received a threat, there's a general assumption among the public at large that the threat automatically means everybody leaves. But with all the companies we're working with, I can't think of a single one that in a knee-jerk reaction evacuates the building simply because a threat was made.

Also read by Tony Scotti

First of all, we know that 98 percent of bomb threats are false. Secondly, if it's a vengeful employee who wants to create disruption or, for example, it's Friday afternoon and someone decides they want a long weekend, they might call in a bomb threat.

Whatever the motivation might be, there's a definite trend that if you automatically evacuate the building, that pretty much ensures that you haven't had your last bomb threat. You're going to see more.

There are some other factors that are not generally considered. One is that, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives, it's generally accepted that 80 percent of devices—roughly 8 of 10—that are planted are not left inside the building and but outside, on the perimeter. That's the most effective place to put a bomb because it's easier to get access. Consequently, if we take people that may be relatively safe inside the building and tell them to evacuate, we may have just taken them to straight to the device.