A half-dozen people were gathered around the tasting bar at the Henley Vaporium in SoHo on a recent Friday evening. Behind the bar, two vapologists in white lab coats stood before a selection of dozens of tiny bottles, each containing liquid nicotine. The customers, all students or young professionals, leisurely inhaled on their so-called vape pens. Clouds of mist curled upward and vanished. A slightly sweet smell lingered in the air.

The vapologists — the title was actually stitched on the breast of each lab coat — were there to help guide them through the array of gadgetry and e-liquid flavors, which come in nearly 100 varieties, like butterscotch, blueberry and crème brûlée. The most popular at the Henley is Swagger, a blend of vanilla, caramel and tobacco flavors.

After an hour sampling the “juices,” Chris Gsell, 39, a director of product development at a nearby ad agency, settled on creamy banana. “It’s delicious,” he said between pulls from his vape pen.

When you draw on an electronic cigarette (or push a button on the fancier versions), a sensor activates a battery that causes a heating element to vaporize the nicotine solution in a cartridge, emitting a fine mist. The disposable e-cigarettes available at bodegas can cost as little as $10; the Henley offers vape pens that cost up to $250, but most are far less expensive. (The liquid nicotine is $12 per 12 milliliter vial and lasts about as long as four packs of cigarettes.) Mr. Gsell uses a refillable, $53 e-cigarette, whose battery packs a lot more punch than the disposable ones. An e-cigarette advocate was standing near the door at the Henley, urging customers to contact the New York City Council to oppose a bill limiting the use of e-cigs that was to be voted on the next week. The response was enthusiastic, but in the end it would not matter. Six days later, the proposed ban on using e-cigarettes wherever smoking is now prohibited became the law.