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Forget a foosball table. Vaping an e-cigarette at your desk is the new workplace benefit of choice.

Just eight years after their introduction in the U.S., e-cigarette devices have expanded to a nearly $2 billion industry. Last week, the FDA took the first stepsto extend its authority from traditional tobacco products to the new devices. Meanwhile, employees are using e-cigarettes and, in the absence of firm federal guidelines, some managers are making their own determinations about whether to allow them in the office.

Cheryl Dooley, CEO of the Ebsco Spring Company in Tulsa, Oklahoma, bought her 28 smoking employees $100 vaping devices and allows them to be used in the company building. She did it after switching to a nicotine vaporizer helped her kick a 40-year, one- to two-pack a day habit that led to a blood clot forming in her lung.

"Every smoker wants to quit," she said, and if she could switch from traditional cigarettes to ones that use a battery-powered atomizer to steam liquid nicotine into an inhalable gas, she wanted her employees to benefit, too. "They're like family to me."

She's also seen an uptick in productivity.

"Nobody's sneaking out," she said. "The office people are always at their desk." The previously high-traffic "Smoke Hole," a covered picnic bench area set aside as a designated smoking area, is largely empty.

"Nationwide, it's a don't ask, don't tell kind of thing."

No wonder that some employers, mainly small business owners, are letting their workers fire up e-cigarettes inside the office. Its novelty means numbers are hazy, said Greg Conley, a board member of the American Vaping Association, which receives funding from both e-cigarette companies and donations.

"Nationwide, it's a don't ask, don't tell kind of thing," said Conley.

Ten states and 172 cities and counties have enacted laws restricting or prohibiting the use of e-cigarettes in certain workplace venues. While there is limited data, and the water vapor of e-cigarettes is viewed by users as less harmful than traditional smoking, a 2013 study published in the International Journal of Hygiene and Environmental Health found vaping did worsen air quality. Other studies have also found trace amounts of ultrafine pollutants in the vapor of e-cigarettes.

All the large-scale companies contacted by NBC News said that the use of e-cigarettes was banned in the workplace under their existing tobacco policies.

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AT&T spokesman Marty Richter said its facilities were "tobacco free" and prohibited electronic and smokeless cigarettes along with any "other tobacco-containing products." UPS said it maintains a "smoke-free work environment," and Home Depot and Kroger both said they treated e-cigarettes the same as "regular cigarettes." GE, CVS, Wal-Mart, McDonald's and Target likewise ban e-cigarettes from the workplace. At the Cleveland Clinic, a ban against hiring smokers also extends to e-cig users.

Most Americans also say they're against vaping in the office. Sixty-five percent of respondents in a 2014 Harris Interactive survey of 1,011 adults, commissioned by electronic cigarette maker Mistic, said they disapproved. But some managers will let it slide as long as there are no complaints.

Eric Bowler, a 28-year old software developer in Manassas, Virginia, takes about 10 puffs a day at his desk. He exhales it into a small desk fan to dissipate the vapor so it doesn't bother his co-worker, who sits at a desk 4 feet away.

"Only one boss ever saw vapor coming out of my mouth. He said, 'Whoa, what is that?' I said, 'Just vapor.' He chuckled and smirked and walked away."

Then there's the clandestine approach.

"I suspect there's plenty of 'vaping in the boy's room,''' said Conley.

Taking a few discreet puffs seems to be more accepted at smaller firms and creative ventures. "I see them around," said Sterling Proffer, general manager of the edgy, youth-oriented VICE News in Williamsburg, Brooklyn. At a co-working office space in Manhattan rented by tech startups, operational manager Karen James says she's seen through the glass doors several clients use vaporizers in their offices.

"I have not received any complaints regarding any of my clients vaping, and until that happens my CEO is unconcerned about enforcing anything," she said. "The vapor dissipates too quickly, if we exhale it at all, and leaves no lingering odors."

And when allowing vaping improves the bottom line, it's hard for a manager to say no. Even in the stuffy world of insurance.

"They're more productive. They're at their desks more often. The odor problem is gone."

"It was a distraction," said Carol Keiling, president of Safety Harbour Insurance Inc., in St. James City, Florida, of her employees' previous smoking habits. Frequently she found customers would have to be told to wait for a call back because their agent was outside on an "ill-timed" smoke break.

Then one of her employees started using an e-cigarette. At first she was banished outside with the other smokers, but after Keiling, a non-smoker, realized there was no odor, she relaxed her policies.

Now as long as there are no customers present, she lets the three of her employees who are former cigarette smokers freely vape at their desks inside the five-person office.

"They're more productive. They're at their desks more often. The odor problem is gone."

Gone, too, is the toe-tapping and fidgeting when a smoker had to sit with a client for more than 45 minutes. If they're really craving a nicotine fix, they can say they're grabbing a file and go around the corner and take a few puffs and come back. The cavalcade of coughing and hacking that used to start every morning has also evaporated. Sick days and colds are down, she added.

Letting her workers vape at their desks is also saving Keiling on the company's health insurance plan.

Now when the group plan questionnaire asks, "Do they use tobacco?" she checks off "no." The FDA hasn't said whether the nicotine in the "juice" loaded into e-cigarette cartridges, derived from tobacco, is itself considered tobacco.

"Technically they're non-smokers now," said Keiling.