TULSA COUNTY, Oklahoma - You see people doing it in stores, at sporting events and maybe even at work. Thousands of Oklahomans are trading smoke for vapor with electronic cigarettes.

They're marketed as safe, but how do we know?

From stores in Tulsa to Oklahoma City, and across all of Oklahoma, there's a steady stream of e-cigarette customers; and a growing list of choices.

E-cigs look very similar to regular cigarettes, but instead of tobacco, the device contains liquid nicotine which turns into vapor that smokers inhale.

Rob Ragan, who owns six E-Cigarette stores, said the e-cigarettes mimic every part of the smoking addiction.

"The hand to mouth motions, the chemical addiction to nicotine, seeing the smoke, even down to the inhalation, exhalation of it," Ragan said.

And that's why they're so helpful in kicking the smoking habit. Ragan said it even helped him stop smoking after more than two decades, when nothing else worked.

"23 and a half years. I smoked two packs a day. I was a freight train," Ragan said. He said it helped in just a matter of weeks.

But some health experts wonder if e-cigarette users are trading one bad habit for another.

Cardiologist Jeffrey Sparling said it's too early to know if e-cigarettes are a healthier alternative.

"In the history of medicine there are plenty of products thought safe, that many years on down the line, end up causing trouble," said Sparling.

Others wonder if e-cigarettes could open the door to some tobacco products.

Dr. Tom Frieden, CDC Director, said, "Middle schoolers and high schoolers are still developing, and research shows that their brains are even more susceptible to nicotine addiction."

"This is a wild west industry. There is very little regulation. Consumers really have no idea what they're ingesting," Sparling said.

At Ragan's Vaporkings stores, no one under 18 can even enter the business. He says the e-cigs are not intended for someone picking up a habit from scratch. Instead, they're to help people stop smoking.

"This is about harm reduction, not about harm elimination," said Ragan. "We let people know first of all, if they're really concerned about the effects of it, don't use any at all."

20 states currently ban the sale of e-cigarettes to minors. Oklahoma is not one of them.

There is at least one state bill planned for the upcoming legislative session that will expand the definition of tobacco products to include all nicotine delivering products, with the exception of government-approved nicotine patches and gum.