Los Angeles: A discreet gadget, supposed to help grownups quit smoking, has landed in the hands of high school children, who suck on nicotine vapours in classrooms, a study has found.

The gadget called JUUL is little bigger than a pack of gum. The study of 80,000 tweets shows that the JUUL vapouriser is widely used among high school, middle school and even elementary school students in the US.

"We found young people talking about using JUUL on school grounds, in classrooms, in bathrooms, in the library, at recess and during gym," said Jon-Patrick Allem, from University of Southern California in the US. "JUUL vapours dissipate quickly, unlike the telltale cloud of previous e-cigarette 'vaping' devices, so it's a way for kids to use nicotine undetected," said Allem said, lead author of the study published in the journal Drug and Alcohol Dependence.

The device consists of a USB flash drive-powered vapouriser that is easily concealed. Users insert cartridges called JUULpods containing nicotine salts found in tobacco leaves. The device converts nicotine into steam that delivers a nicotine wallop; one JUULpod delivers about as much nicotine as a pack of cigarettes.

The device is marketted as a "smoking alternative" for adults trying to quit, but posts to Twitter show that minors use it to "vape" at school without being caught. Nicotine use of any kind is known to be addictive and harmful to adolescent brain development. Allem said that in a sample of more than 80,000 posts to Twitter, about 1 in 25 mentioned using JUUL at school. Some of the tweets even link to videos of kids using JUUL.

"Despite JUUL's branding as a smoking alternative, very few Twitter users mentioned smoking cessation with JUUL," the study found Researchers observed that roughly 1 in 350 Twitter posts mentioned using JUUL to quit smoking, far less than posts about use at school.