In October, Ms. Saunders convened a student advisory board to discuss how to approach e cigs. They said What s an e cig? Ms. Saunders recalled, and she showed what she meant. They said That s a vape pen.

Health officials worry that such views will lead to increased nicotine use and, possibly, prompt some people to graduate to cigarettes. The Food and Drug Administration is preparing to issue regulations that would give the agency control over e cigarettes, which have grown explosively virtually free of any federal oversight. Sales of e cigarettes more than doubled last year from 2012, to $1.7 billion, according to Wells Fargo Securities, and in the next decade, consumption of e cigarettes could outstrip that of conventional cigarettes. The number of stores that sell them has quadrupled in just the last year, according to the Smoke Free Alternatives Trade Association, an e cigarette industry trade group.

The emergence of hookah pens and other products and nicknames seems to suggest the market is growing well beyond smokers. Ms. Zacks was among more than 300 Bay Area high school students who attended a conference focused on health issues last month on the campus of the University of California, Berkeley. Many students talked about wide use of e hookahs or vaping pens saying as many as half of their classmates had tried one but said that there was little use of e cigarettes.

Ms. Zacks said the devices were popular at her high school here. E cigarettes are for people trying to quit smoking, she said, explaining her understanding of the distinction. Hookah pens are for people doing tricks, like blowing smoke rings.

James Hennessey, a sophomore at Drake High School in San Anselmo, Calif., who has tried a hookah pen several times, said e hookahs were less dangerous than e cigarettes. He and several Drake students estimated that 60 percent of their classmates had tried the devices, that they could be purchased easily in local stores, and that they often were present at parties or when people were hanging out.

E cigarettes have nicotine and hookah pens just have water vapor and flavor, said Andrew Hamilton, a senior from Drake.

Actually, it is possible for e cigarettes or e hookah devices to vary in nicotine content, and even to have no nicotine. Mr. Querbach at Romman said that 75 percent of the demand initially was for liquids with no nicotine, but that makers of the liquids were expanding their nicotine offerings. Often, nicotine is precisely the point, along with flavor.

Take, for example, the offerings of a store in San Francisco called King Kush Clothing Plus, where high school students say they sometimes buy their electronic inhalers. On a counter near the back, where tobacco products are sold, are several racks of flavored liquids that can be used to refill e cigarettes or hookah pens. The flavors include cinnamon apple, banana nut bread, vanilla cupcake, chocolate candy bar and coconut bomb. They range in nicotine concentration from zero to 24 milligrams about as much as a pack of 20 ordinary cigarettes but most of the products have some nicotine. To use the refills, it is necessary to buy a hookah pen, which vary widely in price around $20 and upward.

It is also possible to buy disposable versions, whether e cigarettes or hookah pens, that vary in nicotine content and flavor. At King Kush, the Atmos ice lemonade flavored disposable electronic portable hookah promises 0.6 percent nicotine and 600 puffs before it expires.

Emily Anne McDonald, an anthropologist at the University of California, San Francisco who is studying e cigarette use among young people, said the lack of public education about the breadth of nicotine vapor products was creating a vacuum so that young adults are getting information from marketing and from each other.

We need to understand what people are calling these before we send out large surveys, Dr. McDonald said. Otherwise the responses do not reflect reality, and then you re back to the beginning.

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