explosion, it would have probably been a very big fire. >> the federal government has trained more than 300,000 first responders. they see firsthand what explosives like this briefcase bomb can do. >> obviously, it has done more damage to our manican. >> reporter: most of the teaching is in a classroom setting. seeing the explosions and the aftermath is what really hits home. >> three, two, one. . >> you can see the blast. >> right over here, we have spring hangers. just by that, we can tell exactly where the explosives were placed inside this