Last weekend, 14-year-old Ashley Long told her parents she was going to a slumber party. But instead of spending the night watching videos and eating popcorn two blocks away, she piled into a car with a bunch of her friends and rode to a condo in Medford, Ore., where police say the big sister of one of her friends was throwing a party with booze and marijuana.

After drinking on the drive, and downing more drinks in the condo, it came time for Ashley to take her turn on a tank of helium that everyone else was inhaling to make their voices sound funny.

"That helium tank got going around," said Ashley's stepfather, Justin Earp, who learned what happened from talking to Ashley's friends at the party. "It got to my daughter. My daughter didn't want to do it. It was peer pressure. They put a mask up to her face. They said it would be OK. 'It's not gonna hurt you. It'll just make you laugh and talk funny.'"

Instead, she passed out and later died at a hospital, the result of an obstruction in a blood vessel caused by inhaling helium from a pressurized tank.

It's a common party trick—someone sucks in helium to give their voice a cartoon character sound.

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But the death exposes the rare but real dangers of inhaling helium, especially from a pressurized tank.

Dr. Mark Morocco, associate professor of emergency medicine at the Ronald Reagan Medical Center in Los Angeles, said what happens is similar to when a scuba diver surfaces too quickly. A gas bubble gets into the bloodstream, perhaps through some kind of tear in a blood vessel, and can block blood flow to the brain, causing a stroke.

The gas is also commonly seen in suicide kits—mail-order hoods sold out of Oregon and elsewhere that can be attached to a helium tank by people who want to kill themselves. In those cases, the helium crowds out the oxygen, asphyxiating a person.

Death from inhaling helium is so rare that the American Association Poison Control Centers lumps it in with other gases, such as methane and propane. Only three deaths were recorded in 2010, said spokeswoman Loreeta Canton.

It's important to remind kids that ingesting any substance—for the sake of getting high or just changing their voices—can be dangerous, said Frank Pegueros, executive director of DARE, Drug Abuse Resistance Education.

Pegueros said the first defense is for parents to tell their kids about the dangers of certain substances. He said kids need to also ask themselves whether going along with the crowd at a party is worth it.

"Peer pressure is a very potent force," he said. "We've all gone through it growing up."

"It's getting somebody to pause and think and evaluate the situation and determine, is this something that's going to have a bad consequence," he said.

Police have arrested 27-year-old Katherine McAloon, who lived in the condo, on charges of providing alcohol and marijuana to minors. Four men who were at the party have been questioned by police, but have not been charged, said Medford Police Lt. Mike Budreau. More charges may be filed after police turn over their evidence to the district attorney.

Ashley was a goofy, nerdy eighth-grader who struggled with her weight, was just starting to notice boys, got top grades in school, had posters of Justin Bieber all over her room and wanted to grow up to be a marine biologist, said her mom, Loriann Earp. The family moved from Grants Pass, Ore., to Eagle Point about a year ago, and Ashley had just gotten over the difficulty of adjusting to eighth grade in a new school.

Justin Earp said the kids had four wine coolers each in the car, and four mixed drinks at the condo, before they started passing around the helium.

Police said it was an 8-gallon canister, the kind you can buy at many stores. The kids were taking hits directly from the tank.

When Ashley passed out, someone tried CPR. Then they called 911. Paramedics tried to revive her and took her to the hospital.

"About 11:30 we got a phone call from police saying they were doing CPR on our daughter," said Justin Earp.

At the hospital, they were told that Ashley had died.

Her family has set up a foundation, Ashley's Hope, to spread the word about the dangers of inhaling helium.

Loriann Earp feels like her daughter was stolen from her.

"My whole chest is collapsed and my heart is broken," she said through sobs. "I don't understand."