It's been more than a decade since the feds started warning about the potential for pressure cooker bombs. But we're still essentially powerless to combat a weapon that's alarmingly easy to make.
Pressure cooker bombs may seem like the latest trend in terrorism, but a 2004 memo from the Department of Homeland Security dates their use back to 2001. That year a pressure cooker bomb killed police officials in a convoy in Nepal.
In the United States, this seemingly innocuous kitchen tool was used in an attempt to blow up Times Square in 2010.
Then, there was Boston. The 2013 attack involving pressure cooker bombs killed three people and injured over 250 others.
Justin Kelley is a bomb expert with decades of experience responding to and teaching about bombing events. Now he's Managing Director of Operations for MSA Security. He knows why pressure cooker bombs have caught on and have continued to be difficult to stop.
"To make a pressure cooker, all the parts and components are legal," Kelley explained. "It doesn't arouse suspicion. Today it might. But if you go into some places and go in and buy a pressure cooker, there are no bells and whistles going off because it's a valid product."
It's not just the accessibility of materials that makes pressure cooker bombs an easy option. There's a ton of information about construction on the web. A Jihadist magazine even posted a recipe called "Make a Bomb in the Kitchen of Your Mom."
It's being taught out there. People are researching it and seeing it's a very simple device to make.
So, how can we fight back against pressure cooker bombs? Watchful eyes. And not just from people who may take the government's advice to say something when they see something. Bomb detection dogs can also be a useful tool.
Even a tightly sealed pressure cooker can't keep a bomb detection dog from sniffing out a range of explosive odors. Kelley says his company's dogs are imprinted on 32 initial scents, grouped in families that eventually give them familiarity with hundreds of odors.
Bombings like New York and New Jersey often cause a spike in demand for bomb detection dogs.
"It really should be a steady state. The threat doesn't go away because it's off the pages or off the news," Kelley said.
In addition to the protection provided at airports, train stations and other large venues, some cities are putting canines on routine street patrols.
They're not sent in once a pressure cooker is found. Instead they can help sniff them out. But the work these dogs do requires constant training and reinforcement. Demand is high and it's hard to keep a constant supply of qualified bomb detection dogs out there.
Age is a major factor. Kelley says most bomb detection dogs only stay on the job until about age 8.