HAZARDOUS DEVICES SCHOOL

On a chilly winter afternoon, five men stand in a circle outside a strip mall, their lips pursed and brows tight with concentration. The group includes a police officer from Monroe, Louisiana; another from Manatee County, Florida, wearing a hunter's orange stocking cap; and an eager young member of the Arlington, Virginia, fire department in his dark-green fireman's jumpsuit. The men are talking deliberately, with long pauses, as they think through how to deal with the nasty problem at hand: A hundred yards away, in the strip mall, they have just discovered a motel room filled with explosive material.

Inside the room at the Rocket City Hotel, the bed frame has been thrown up against the wall. A piece of brown parchment paper covered with chemical equations is taped up next to it. A single light is on, in the bathroom, illuminating a beaker on a hot plate. There are improvised detonators and pipe bombs all over the room.

"You said the bathtub was filled with some kind of powder?" an FBI special agent asks Justin Scott, the Arlington firefighter, who is wearing a baseball cap with his jumpsuit. Scott has just returned from a reconnaissance mission into the room, where he found syringes, a box of baking soda, and a basin full of citric acid.

"The powder is drying on a big sheet in the bathroom," Scott says.

"What color is it?"

"Whitish-gray."

The Rocket City Hotel is not a real hotel. The strip mall was built by the FBI in 2004 and sits on the campus of its Hazardous Devices School (HDS), part of the Redstone Arsenal, a thirty-eight-thousand-acre U.S. Army facility in Huntsville that's also home to the Pentagon's Missile Defense Agency, NASA's Marshall Space Flight Center, and the Army's Aviation and Missile Command. As you walk around the campus, what sound like large explosions ring out every few hours from distant corners.

"Today is a homemade explosive lab, tomorrow morning's gonna be a suicide bomber, and tomorrow afternoon will be a car bomb."

The men standing in a circle are trainees, learning how to approach, identify, defuse, and generally keep humans safe from explosive materials. The strip mall also contains an auto repair shop and a diner and is one of twelve villages built by HDS to simulate real-world situations. There's an airport baggage carousel, a church, and a movie theater. (The marquee advertises The Hurt Locker, the 2008 film about a bomb-disposal team in Iraq that won six Academy Awards including best picture.) At another location, a group of students is figuring out how to remove a suicide vest attached to a mannequin's body.

At the motel, the trainees stand around a white utility truck that carries their equipment—bomb suits, X-ray machines, water cannons, and a robot they've already rolled off the back. They consider the new information from Scott's reconnaissance: Most explosive powders are white or gray, except TNT, which is yellowish. Not much to go on.

As recently as 2014, improvised explosive devices caused 42,627 casualties worldwide. In one six-month period in 2013, there were 172 IEDs reported in the United States alone. Many of these devices are defused without incident, usually by people like the bomb techs in Huntsville—young law enforcement officers drawn to the profession by the promise of doing something more interesting than writing traffic tickets. Every one of these techs—about thirty-one hundred spread across 466 squads—trains here at Huntsville.

"Today is a homemade explosive lab, tomorrow morning's gonna be a suicide bomber, and tomorrow afternoon will be a car bomb," says Ed Marshman, a burly former FBI agent with a white goatee who is now an HDS instructor. "Thursday will be a WMD."

Every trainee must prove an ability to maneuver a bomb robot through an obstacle course. Jonno Rattman

Bomb makers constantly adapt and change their methods over time as new technologies present new ways to cause destruction, and bomb technicians are expected to know everything—DC electricity, robot operation, how to build and countercharge a bomb themselves. Students at HDS start their work in the classroom. In the first room I visited there was a row of mannequins wearing bomb suits from the 1960s to today. At one end of the display a large floor chart showed the relative danger of standing over an explosion, a half-pound block of TNT without fragmentation, at different distances: Four feet away, a bomb tech might suffer hearing loss; from three feet, there's a high chance of severe lung damage; any closer, even in a bomb suit, and survival becomes much less likely.

The chart is displayed prominently, and its presentation on day one is deliberate. At some point, every bomb tech will have to get closer than he'd like to a live explosive. Of course, much of what the techs learn here is designed to prevent that very thing. The day before the motel exercise, Kent Hamann, HDS's chief of basic training, led me into a room filled with dozens of portable X-rays the bomb techs use to glean information about improvised explosives from afar. They come in a variety of setups, but the most common look like large camping flashlights. Hamann pulled up an image from one of the X-ray machines on a computer screen. It looked like a medical X-ray—only instead of a broken ulna, there was a sickening nest of wires connecting a cellphone to an explosive charge.

When Hamann first became a bomb technician in 1984, the preferred tool for disarming a bomb from afar was a shotgun. Today, it is a PAN disrupter. He leads me past a room full of these devices, which look simple—like the barrel of a rifle attached to a stand. A PAN disrupter is a sort of high-tech shotgun—it can fire at varying speeds, depending on the type of bomb that needs disarming, and with different projectiles: sometimes blank shotgun shells, but more often simply water. "Water does not compress, so if we push it fast enough, it does a lot of ripping and tearing," Hamann says later, driving past one of HDS's two demolition ranges. He points down the range at a row of cars, each of which has a hole in the side that looks as if a small asteroid has burst through it. "That was explosively driven water," he says.

PAN disrupters are often attached to robots, and the school stores dozens of them in a dedicated maintenance shop. Bomb-defusing robots first appeared in the field in the 1990s, but they couldn't do much. Today, they're equipped with X-ray machines and can be operated by remote video link. Every bomb squad is required to have one, and all HDS students have to prove their ability to maneuver them through a concrete obstacle course featuring stairs, handicap ramps, and tight corners.

At the motel room, the members of the bomb squad debate their options. They'd prefer not to have a human breach the doorway, but they may not have a choice. They've noticed that the hot plate in the bathroom, with its carafe containing an unknown liquid, is plugged in to the wall. It's an explosion waiting to happen. And there's only one way to neutralize it.

TERRORIST EXPLOSIVE DEVICE ANALYTICS CENTER

A few minutes' drive from the Hazardous Devices School sits an entirely different facility: the Terrorist Explosive Device Analytical Center (TEDAC). If the thirty-one hundred bomb techs scattered across the country are the fingers that defuse each individual bomb, TEDAC is the brain.

Here, every minute of your visit reminds you that you are dealing with the most powerful law enforcement agency in the land. When you arrive, having already gone through one checkpoint that looks like an interstate tollbooth manned by armed guards, your car will be thoroughly searched by a security officer who spends several minutes digging through your trunk before circumnavigating the vehicle, inspecting the undercarriage with a mirror. Once you've gone inside the building, you pass through a metal detector and then hand over your phone, which has to be checked into a locker.

FBI recreation of a book bomb used by the Unabomber. Jonno Rattman

TEDAC is in the process of moving its operations from its old home at the FBI Crime Lab in Quantico to this new $132 million facility. Most of TEDAC, but not all, is now in Huntsville, where it has one operational building and two more on the way.

In spite of the construction, the halls inside always seem to have been recently swept. (In one suspiciously clean lab room, an employee tells me it isn't usually so neat, but they had been working on something they couldn't talk to me about.) The corridors are dotted with clocks showing the current time in Quantico, Baghdad, and Kabul. I saw four or five signs that read "Do not discuss classified info in hallways" on the walls on my limited tour.

The office of Corey Scott, like most of the rooms here, is littered with cardboard boxes of all shapes and sizes, each of them sealed with multiple layers of bright-yellow evidence tape. Any time an analyst at TEDAC examines a document or piece of evidence from any case, he puts it back in its box, adds a layer of yellow tape, and signs his initials to record the chain of custody. One room I visited contained a dozen boxes labeled "Car Search" and "Post-Blast" and "104 Elmora"—the address of a restaurant run by the family of Ahmad Khan Rahami, the man suspected of placing bombs in Elizabeth and Seaside Park, New Jersey; and New York City in September 2016.

Scott is an analyst in the Toolmarks department. When an exploded IED is recovered, or when one is captured early and defused, Toolmarks is typically its final stop at the FBI. (See right.) Biometrics—fingerprints and DNA—determines the who. Chemical Analysis tells the FBI the what. Toolmarks is the how.

I saw four or five signs that read "Do not discuss classified info in hallways" on the walls on my limited tour.

"Toolmarks is the final resting place," Scott says. "It's basically, We don't know what else can be done with it, so send it to Toolmarks."

Wearing rectangular glasses and a blue gingham shirt and slacks, Scott sits down at a comparison microscope. He has brown hair and is of average height. He could pass for an accountant. "I feel like a dentist a lot of the time," he says. He lines up pieces from two different explosive devices next to each other, revealing that they have nearly identical markings. They may have been made by the same person, or at least with the same blade or hammer. "We can link devices that come from two different countries back to the same manufacturer," he says.

Bomb remnants can spend years at TEDAC, with the goal of giving law enforcement everything they need to find and prosecute individual bomb makers anywhere in the world. The first device that ever arrived at TEDAC, back in 2003, was an Iraqi bomb attached to a doorbell. At the height of the insurgency, the facility received as many as five hundred boxes a day filled with evidence, some from Indonesia, Pakistan, and Saudi Arabia. It has now examined more than 105,000 devices, most of which are stored in a warehouse in Redstone.

HDS

That's the diaper," Justin Scott says, as the other officers attach a layer of Kevlar around his groin. He's getting ready to enter the motel room. Modern bomb suits weigh eighty pounds and come with an exoskeleton spine to protect against blasts that send bomb techs flying. It takes two of the other trainees to lift the chest protector up and over Scott's head.

It's gotten colder and a light rain falls, but Scott is sweating even before he begins walking the hundred yards to the motel. A technician can typically last twenty minutes in a bomb suit before exhaustion begins to impair his decision-making skills. Before that time is up, Scott will have to unplug the hot plate and dispose of the improvised detonators, a task with no high-tech solution.

"What should every bomb tech have in his possession?" Marshman, the HDS instructor, says before Scott begins his long walk.

"One of those things old ladies use to pick things up off the ground?" says the officer from Louisiana.

"Bingo. If that improvised det goes off in your hands, what's gonna happen? You're Captain Stumpy," Marshman says, picking up a blue trash grabber. "If it goes off at the end of this, you've just got to clean your bomb suit."

The tape and analyst's initials indicate the chain of custody. Jonno Rattman

Unfortunately, there are some occasions when something as simple as a trash grabber is the best technology a bomb tech can use. After a large explosion, civilians will immediately turn and run, often dropping whatever they've got in their hands: purses, water bottles, plastic bags, backpacks.

"Go back and look at the pictures," says Hamann, of the aftermath of the 2013 Boston Marathon bombing. "There are backpacks everywhere, and somebody's got to clear every one of them." There's no time to deploy a robot when another bomb could go off at any second. Bomb-sniffing dogs are worthless when an entire scene is covered in explosive debris.

Hamann's face morphs into a look of extreme distaste. "At a certain point," he says, "it's cut open and look."

TEDCC

The job of a TEDAC examiner is less immediately exhilarating than a bomb tech's—there's good reason The Hurt Locker won best picture while The Kingdom (2007), based on a TEDAC investigation, is largely unmemorable. TEDAC is a place for people who would rather engage in focused study in quiet lab rooms than walk downrange, hearts pounding, in bomb suits. And yet no job related to homemade explosives is entirely safe. In another room, Colin Pollard, a chemist who works in the TEDAC Improvised Explosives Detection and Synthesis Center (TIEDS), stands next to a fume hood in a lab filled with beakers, mixing the elements necessary to make a compound called silver fulminate. "It's a very angry explosive. I'm trying to make it without it bursting in flames," he says, cheerily.

Pollard came to TIEDS from Los Alamos and Sandia, two of the government's most elite laboratories, where safety regulations were much stricter. TIEDS can set off an explosive with just a few hours' notice to clear the airspace above the test site. They don't want to accidentally pick off a small aircraft. As Pollard says, "We have the capability to make any explosive known to man here."

Once he's done mixing, Pollard scoops out a pinch of silver fulminate, a white powder, puts it on a plate, and sculpts it into a neat pile. He hands me a pair of earphones, then smacks it with a hammer while I wince. There is a loud pop. This is an impact test, he says, just one of the many kinds of exams the chemists at TIEDS conduct on dangerous materials, along with heat, friction, and electrostatic energy. On the demolition range, they use high-speed cameras to determine the size and velocity of any of the fragments that fly off in different directions during an explosion, and pressure gauges to determine the force of the explosion's shock waves. In the lab, one of Pollard's colleagues pulls up a video clip from a recent test of ammonium nitrate and nitromethane, an especially explosive mixture. The clip shows three distinct shock waves radiating across the screen in the first instants after the explosion, before the dirt on the ground even begins to kick up.

"It's a very angry explosive. I'm trying to make it without it bursting in flames," he says, cheerily.

Of course, most terrorists don't use laboratory-grade equipment to make their bombs. "We need to do it our way first, so we know what we're dealing with," says Kenneth Lee, who runs TIEDS. "But then we try to do it the same way they would." That means buying ingredients at a home center or hardware store and mixing them in plastic buckets and bathtubs. In one room, the TIEDS crew has a grinder that reads "Fresh Ground Coffee"—except the word Coffee has been crossed out and replaced with Explosives. Why grind explosive materials in a coffee grinder? It increases their surface area, making the explosion more deadly. TIEDS' experiments show exactly how much damage can be done by explosives cooked up in makeshift home labs by terrorists, so that engineers can design buildings to withstand potential blasts.

As I walk through TEDAC's various departments, I feel simultaneously encouraged and disheartened. The attention to detail is stunning: In one room, an examiner is packing up a device from Afghanistan, armed by a Casio F-91W digital watch, to send over to HDS for use in training. Another analyst is doing tests on a bomb suit to determine why it caused a technician to pass out. To witness this work being done is to feel a little bit safer in the world.

But then there are those yellow-taped boxes. So many of them, in so many rooms. The number of devices flowing into TEDAC has declined since the height of the wars in Iraq and Afghanistan, but so many arrived then that some still remain unexamined. There are rooms and rooms of these boxes, some containing evidence from bombings we've heard about. Most contain items from the ones we haven't. No matter how skilled the analysts are, the sheer scale is terrifying.

Robots trains students in imitation bomb-making labs. Jonno Rattman

HDS

There's a memorial on the grounds at the Hazardous Devices School. Every aspiring bomb tech visits the site on his or her first day. The memorial eulogizes the fifteen American public-safety bomb technicians who have been killed in the line of duty, stretching back to 1903, when the New York Police Department created the country's first dedicated bomb squad. The first five plaques are all members of the NYPD. The most recent, from 2008, commemorates an Oregon bomb tech killed by an IED at the site of an attempted bank extortion. The sixteenth plaque is left intentionally blank, to remind students that no matter how well they are trained, and how safely they act, they have chosen an extraordinarily dangerous profession.

The instructor's point in bringing the trainees here is this: Know the risks of what you've chosen to do. But also know that you are a hero. The stakes for ordinary civilians are monstrous if you fail. That day at the motel, Justin Scott carefully picks up each of the improvised detonators with his trash grabber and carries them outside, one at a time. He breathes heavily, laboring to finish his job before exhaustion overcomes him.

In the white truck, his colleague from Manatee County monitors the situation through the robot's three different cameras. When the detonators have been removed from the building, one of the other students meets Scott outside the motel with a shovel. They walk carefully over to a plot of grass, where they mime digging a hole and setting the detonators inside. If this were a real incident, the hole is where they would safely blow everything up, while everyday citizens driving by the motel would never know how close to danger they had come.

"We save the world again!" the instructor yells to the crew.

HOW TEDAC WORKS

When a device arrives at the Terrorist Explosive Device Analytical Center, it moves through three different types of examination based on what law enforcement or intelligence agencies need to know most quickly. "They tell us what they want, and we start pushing evidence out immediately," Mark Whitworth, who runs TEDAC's forensics unit, says. Here's how it works.

Situation: A bomb has gone off. The suspect is in custody.

Department: Biometric Analysis

Explosions do not always destroy DNA—traces can be found in hairs or droplets of sweat—or fingerprints. TEDAC examiners scour for prints using shortwave ultraviolet light, fluorescent dye sprays, and a refrigerator-size tank that can vaporize superglue to allow it to settle on the prints, revealing and preserving them. Viable prints are cross-checked on the FBI's Next Generation Identification biometric system, which spits out the top twenty possible matches but is so precise that investigators typically never need to look beyond the first three.

Situation: A bomb lab has been found with no bombs in it.

Department: Chemical Analysis

Gas chromatographs and mass spectrometers can determine the chemicals used, which can provide clues to where, how, and by whom a device was made. The HDS students who were clearing the fake motel room, for example, found urea nitrate, a chemical rarely used by domestic bomb makers. Urea nitrate was used by the bomber of the World Trade Center in 1993, and the foiled millennium bomber, both of whom were foreign Al-Qaeda operatives. The presence of urea nitrate might indicate that the motel chemist had come from overseas.

Situation: Biometric and chemical analysis have revealed nothing.

Department: Toolmarks

Certain cuts or scrapes might come only from a particular blade made by a particular manufacturer in a particular country. A torn piece of tape can be matched to the remaining roll found in a suspect's home. The way in which a wire was cut can reveal the type of tool used. Over time, clues can reveal an unwitting signature: The Unabomber, for instance, always skinned the labels off of his batteries and wrapped them in monofilament tape.

BOMB TOOLS

PAN Disrupter

This device, basically a high-tech rifle, allows a bomb tech to choose different rounds to disable a pipe bomb versus a pressure-cooker bomb, or a device with a remote control versus one with a timer. To disarm more sophisticated IEDs, bomb techs sometimes fire multiple projectiles (such as blank shotgun shells or water) at different speeds within milliseconds of one another.

Total Containment Vessels

A trailer-mounted lead-and- steel sphere capable of containing a blast with the power of up to 25 pounds of TNT. Inside the vessel a bomb can be transported through city streets without the need for evacuation. If an explosion does occur, the fragmentation and shock wave will be contained while pressure escapes from a series of small vents. Some versions can be outfitted to contain the effects of biological or chemical weapons.

This story appears in the April 2017 Popular Mechanics.