Teens learn on YouTube to make the "bombs" with a few cheap, household items, then travel in groups late at night — eager to hear the boom, laugh with friends and gauge whatever damage they've wrought.
According to Lt. Carlton Saunders of Howard County's office of the fire marshal, teenagers consider it a prank when they experiment with "bottle bombs," which have been found over the years in counties all across the Baltimore region.
The explosions are rarely associated with damage greater than a busted mailbox, and are even more rarely associated with injuries, Saunders said.
But making a bottle bomb — generally a plastic bottle that explodes after a chemical cleaner, a piece of aluminum foil and a little bit of water are placed inside to cause a gaseous chemical reaction — is no laughing matter, he said.
"There is a whole gamut of things that could go wrong and cause harm to people," said Saunders, who runs the county's Juvenile Fire Setters Intervention Program, which for the last two years has had a special "bottle bomb component" for teens who've been caught exploding the devices.
Howard's focus on bottle bombs as part of its diversion program is rare in the Baltimore region, but bottle bombs — also known as "chemical reaction devices" — are not, according to multiple police departments.
"They've been around for a long time," said Elise Armacost, who began fielding an influx of phone calls about bottle bombs last week after an email warning about the devices went viral around the county.
There's been no recent uptick in bottle bomb explosions in the county, with two so far this year compared to 13 in 2011, none of which resulted in an injury, Armacost said.
But people should be aware of the dangers, she said.
"They can cause serious injury, especially if they're placed in a mailbox or some container where they would create shrapnel if they exploded," Armacost said.
Last month in Anne Arundel County, an 18-year-old woman was taken to University of Maryland Shock Trauma with serious hand injuries after a homemade bottle bomb she made exploded.
Monica Worrell, a spokeswoman for the Harford County sheriff's office, said there was a string of bottle bomb incidents in that county last year, though she couldn't remember any serious injuries.
Howard police publicly warned residents of bottle bombs in March, saying police had received five reports of bottle bombs since the beginning of the year, and nine in 2011.
"If a citizen sees a suspicious container, typically a plastic bottle that is significantly expanded and deformed, this is a sign that the device could be a bottle bomb and may explode," police warned.
In February, three Howard teens were investigated for destroying multiple metal mailboxes with bottle bombs, and had to take Saunders' course as a result, the warning said.
Saunders said most teens who come through his course never meant to hurt anyone or cause significant damage, so it's important to him to convey the seriousness of the devices to them.
He tells them the devices could kill a toddler, or severely wound an adult close to the bottle when it explodes.
He also reminds them their parents will be responsible for any damage their pranks may cause.
A few years back, he says, the parents of three boys in western Howard had to pay $15,000 to replace the components of a large soda machine, which the boys had put a bottle bomb inside.
Then there are the legal repercussions for the teens, Saunders says.
Federal officials have been taking the creation of such devices far more seriously since the Sept. 11 attacks, and will charge a teenagers with felonies if they think they intended to cause damage, Saunders tells those in his class.