Students are Juuling in class, in the bathrooms and in the hallways.
Jordan Alonzo is a senior at Berkeley High School is part of an anti-tobacco student group and say this past year Juuling, or vaping with a gadget that looks like a flash drive, has really taken off and he's doing what he can to stop it.
Each Juul cartridge—which lasts about 200 puffs—has as much nicotine as an entire pack of cigarettes.
Keyanna Hardison, a sophomore at Berkeley High, says it's hard to find friends that don't Juul. "Two of my friends don't do it but the rest of them do," she said.
The teens said adults and parents are in the dark about the new craze because it's so easy to hide.
Junior Jessica Guiza showed how easy it is to slip the little device up her sleeve, saying "if you never saw one you wouldn't know that this holds nicotine so a lot of people in class they'll hold it like this and then hit it like that or they will hold it because it's small so you can hold it in your hand or I'll see people tuck it in their backpack really quick and just like lean down." Senior Eli Waldman says kids do it because they get a head rush.
The Juuling industry has exploded into a $1.16 billion industry with a 40 percent expansion last year.
Juul Labs is credited with a lot of that growth. It is a Bay Area company started by two Stanford graduates back in 2015. As of March, Juul sales accounted for more than half of all U.S. retail sales. There are a lot of other brands, like the Sourin, the Phix but Juul seems to have taken over the market.
The same teens who think cigarettes are gross now seem think these devices are cool. Hardison said her friends think its healthier saying "most of them say it's not bad they just like doing it for the head rush and it's better than smoking a cigarette."
Juul stands out from other companies in part because their pods have the same amount nicotine as a pack of cigarette, which is significantly more than most e- cigarettes. The company declined KTVU's request for an on camera interview but gave us a statement that said in part, "Juul Labs' mission is to eliminate cigarette smoking by offering existing adult smokers a true alternative to cigarettes." California law requires users to be 21 and older.
But doctors say they are worried about the perception that vaping can't hurt you.
Dr. Wilson Tsai is a thoracic surgeon with the Bass Medical Group and recounted a recent conversation with a patient who told him, he doesn't smoke. Tsai said the patient "had very significant lung damage and I said besides cigarettes what are you smoking and he said marijuana and e-cigarettes thinking that was safe alternative."
Dr. Kristina Kramer is a cardiac pulmonologist with Bass Medical and says the FDA has been trying to figure out how to handle the popularity of Juuling. Dr. Kramer says "one of the reasons why the FDA doesn't promote e-cigarettes is we just don't know what the long term effects are of these devices we don't know if they cause cancer we don't know the long term effects will and it's a big question mark.
There are so many unanswered health questions about impact of the chemicals in e-cigarettes and the more than 15,000 flavors available, but doctors say it's clear that nicotine is bad.
Tsai said "nicotine we know that causes a delay in the prefrontal cortex which is a region of the brain which is responsible for inhibition control or emotional control and by causing that developmental delay especially in adolescents they are more prone to causing addiction and psychiatric issues later in life."
Kramer added "there is a concern that it may be a gateway drug. Children who are exposed to vaping are more likely to try tobacco smoking."
Guiza says a friend who told her she only wanted to Juul at parties is now smoking cigarettes. Many teens say they know friends who can't get through the day without getting a hit.
Juul Labs said it strongly condemns the use of its product by minors. But last month the FDA announced a crackdown on the e-cigarette industry and sent Juul Labs a letter demanding the company turn over documents on marketing and research. The goal is to find out if Juul Labs is intentionally appealing to young people. It is issuing similar letters to other manufacturers.