The growing popularity of electronic cigarettes could be curbed by state regulations that would treat them the same as tobacco cigarettes, under a proposal headed for a vote by the Senate.

A sweeping set of restrictions would prohibit what users call "vaping" indoors and in public spaces and would ban the sale of e-cigarettes and smokeless devices to those under age 18. Backers of the restrictions, which passed a final Senate committee on Monday, say the concerns over secondhand vapors from the devices are enough to include them in Minnesota's statewide indoor smoking ban.

"If you work in a hotel, restaurant, bar or VFW, I'm not sure you want to be forced to choose between keeping your job and being exposed to some unknown array of chemicals being released into the atmosphere," said Sen. Ron Latz, DFL-St. Louis Park.

The Senate bill differs significantly from the far milder House version, which would ban sales to minors and prohibit the use of e-cigarettes in public schools but would not subject the devices to the wider indoor ban.

Some lawmakers question whether it's premature to prohibit vaping indoors entirely, saying there is not enough evidence demonstrating that secondhand vapor is harmful.

"I have not seen the scientific data that says this is dangerous if you're simply in the same room as someone using an e-cigarette," said Rep. Will Morgan, DFL-Burnsville. "I'm a physics teacher. I think we should rely on science for decisions like that."

States including Minnesota have been grappling with how to regulate the emerging e-cigarette industry.

Minnesota has about 200 e-cigarette retailers, about 80 percent of which opened in the past year, and merchants said a sweeping indoor ban would stifle businesses.

"It will make it harder for businesses like ours to survive," said Jesse Griffith, owner of Smokeless Smoking, an e-cigarette store in Woodbury. Many of the stores have become social hubs for e-cigarette smokers, industry officials and store owners said at the Senate hearing.

E-cigarettes do not contain tobacco, but many varieties contain nicotine. There is little consensus yet on whether the vapors exude chemicals that are dangerous to inhale.

Advocates of e-cigs say that the devices are becoming a popular alternative for smokers trying to quit, and that tighter restrictions on their use could discourage that switch — or even drive some back to cigarettes.

"I would ask that you pause before adding another layer of regulation that would be a disincentive for adults to use this legal product," Tom Bryant, director of the Minnesota Wholesale Marketers Association, which represents tobacco merchants. Tobacco and e-cigarette industry officials have all signed on in support of the ban against selling the devices to minors.

The state Health Department last week warned that reports have risen sharply of children consuming the poisonous liquid used to fuel e-cigarettes. Cases reported to the Minnesota Poison Control Center increased tenfold from 2012 to 2013.

A proposed amendment in Senate Commerce to strike the indoor ban from the bill failed by one vote. The bill's sponsor, Sen. Kathy Sheran, DFL-Mankato, said she hopes for a full Senate vote in coming weeks but is not yet confident the indoor ban would survive an attempt to strip it from the bill by a Senate floor amendment.

Support for the indoor ban is weaker in the House. The bill's sponsor there, Rep. Laurie Halverson, said she hopes it gets e-cig restrictions to a House-Senate conference committee.

"We are asking our colleagues to go from zero to sixty on this one. I think people walked into session not even knowing they'd have to deal with this," said Halverson, DFL-Eagan. "The knowledge of these issues is still evolving."