Photograph by Reed Saxon, AP

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Los Angeles International Airport was the scene of dry ice bombs this weekend.

Photograph by Reed Saxon, AP

The Science of Dry Ice Bombs, Like LAX’s

Improvised explosives detonated at LAX rely on basic chemistry.

Although dry ice—frozen carbon dioxide—is often used to ship food products and to dazzle high school chemistry students, it can also be the basis for improvised explosive devices. A number of people have been injured with dry ice bombs in recent years, and two such devices detonated at Los Angeles International Airport (LAX) over the weekend.

On the evening of October 14, dry ice exploded at the Tom Bradley International Terminal in Los Angeles, according to airport police. The blast occurred in an employee restroom that was inaccessible to the general public. There were no injuries reported and flights were not delayed.

Authorities found three plastic bottles in the restroom that had been packed with dry ice; one of the bottles had exploded.

Paul Worsey, an explosives expert at the Missouri University of Science and Technology, told National Geographic that he objects to the media calling the devices "dry ice bombs." He said, "People use 'bombs' for everything, like the 'f-bomb.' But what is important is whether it is really a destructive device, and these aren't."

On Tuesday evening, media reported that 28-year-old Dicarlo Bennett from South Los Angeles was arrested in connection with the alleged dry ice devices. According to police, Bennett worked for Servisair, an airport contractor.

The case had been referred to the FBI, and Los Angeles police detective Gus Villanueva had told the media earlier that there is "no nexus to terrorism at this point."

On Sunday, another plastic bottle filled with dry ice had exploded at the same airport, also in an employee restroom. Terminal 2 was briefly shut down for an investigation though no one was hurt.

Inside a Dry Ice Bomb

It's not the first time that dry ice explosions have made headlines.

In 2011, a high school chemistry student in suburban Chicago lost his left eye after a plastic bottle containing dry ice and water reportedly exploded during a class demonstration.

Family of the Oak Lawn, Illinois, student sued the school, alleging that proper safety precautions, including the issuing of goggles, had not been taken.

Dry ice is very cold, −78.5°C (−109.3°F), and handling it can be tricky. A dry ice bomb can explode within seconds of being sealed.

According to the Oak Lawn suit, the teacher had allegedly sealed the bottle, then passed it around the class so that students could feel the growing pressure inside.

Mitch Andre Garcia, a chemist at UCLA, wrote on his blog that the actions of the teacher were: "Dumb. Dumb. Dumb."

Garcia, who has worked with pressurized dry ice, explained that the frozen carbon dioxide sublimes (or changes) to gaseous carbon dioxide at room temperature. That gas has a much greater volume than the original solid.

"If you put all this volume in a closed container, the pressure will build and build until the container fails and explodes," wrote Garcia. "You make a bomb as soon as you put dry ice in a closed container.  The addition of water accelerates the sublimation, causing the pressure to build up faster."

Garcia added that he has demonstrated dry ice explosions at public events, but he follows a number of precautions. He seals a small amount of dry ice in a two-liter pop bottle and places it under a plastic mail crate to contain the explosion and catch any shrapnel. He has everyone stand back.

"It's really loud," he wrote. "Even with the mail crate atop, the explosion still throws the bottle/crate 5-10 feet in the air."

Garcia noted that making a dry ice bomb is actually illegal in many parts of the country, and can lead to imprisonment.

Worsey said that he isn't surprised a dry ice device injured an eye, because "the eye is one of the most delicate parts of the body and doesn't heal very well." He said, "Generally these things aren't going to damage anything. In this case you have a low-pressure container that will pop, it's like coming up behind someone with a balloon and sticking a pin in it."

Worsey said it is possible to make more dangerous dry ice devices out of stronger, more brittle containers that could produce more harmful shrapnel. But he said there are easier ways to make bombs, including more traditional pipe bombs (out of metal pipes and gunpowder) or even devices made with drano, which is caustic.

Other Dry Ice Bombs

In May, an employee at Disneyland in southern California was arrested for allegedly putting a dry ice bomb in a trash can at the popular theme park.

"This is a simple device," John Goodpaster, an explosives expert at Indiana University-Purdue University Indianapolis, told the news media at the time. "It's not a pipe bomb filled with gunpowder, but it definitely will generate an explosion."

Goodpaster said the size of the explosion can vary based on the container's size and the amount of dry ice used.

Worsey added that he used to amuse his friends by dropping pieces of dry ice in their beer. "It bubbles over and looks cool like a werewolf drink or something," he said. "But the bubbling would take all the gases out of it, and people would get mad because their beer would be horribly flat."

Updated on October 16, 2013 at 12 pm.