Pressure cooker bombs, like the ones reportedly used in the explosions near the finish line at the Boston Marathon, are a common and simple way to make an explosive device, according to a University of Rhode Island chemistry professor.
"It only takes a small amount of black powder to ignite a powerful blast," said Jimmie Oxley, who also is a member of the U.S. Department of Homeland Security Center for Excellence for Explosives, Detection, Mitigation and Response.
She said if you put it inside a common kitchen pressure cooker, you'll have a weapon. The steel container will make fragments which are what do the most damage.
"If you feel the sharpness of those edges, if that hits you, you can see why it takes off an arm. If it was a pressure cooker, it would create frag," Oxley said.
Oxley said of all terrorist weapons, a homemade bomb is the most accessible.
"One of the easiest ones to execute is a bomb because you can take simple materials and cause all kinds of harm," she said.
And a kitchen tool is more easily explained than capped pipes.
"Every now and then it raises suspicion if you buy a pipe with the end caps to go on it. Buying a pressure cooker, probably not as suspicious," Oxley said.
Kenneth Glantz, executive director of the National Domestic Preparedness Coalition, agreed that improvised explosives or IEDs are popular for those looking to create mayhem.
"They are very easy to build. It doesn't take a lot of money. It doesn't take a lot of resources and they're very effective. That's why terrorists use the IEDs," he said.
Glantz says people need to look out for themselves.
"If you see a backpack sitting out by a garbage can or a backpack sitting all by itself and it's suspicious, you want to report something like that," he said.
Oxley predicted from the smoke of the explosion that it might have been black powder, which is what law enforcement officials told the New York Times earlier Tuesday. They said the devices were pressure cookers and were packed with metal to create even more shrapnel and fragments.