New laws have come into force in New South Wales banning the sale of electronic cigarettes to anyone under the age of 18.

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"E-cigarettes" are battery-powered devices that heat a liquid, which may contain nicotine, to create a mist to be inhaled by the user, a process known as vaping.

The NSW Government passed laws in June to address concerns that e-cigarettes could act as a gateway to tobacco smoking in children.

The laws are being rolled out in two stages, with a ban on the sale of e-cigarettes to minors coming into force today along with rules on where product vending machines can be placed.

Police have also been given the power to confiscate the vapour devices from anyone aged under 18.

A ban on vaping in cars and restrictions on the advertising and display of the devices will come into effect from the December 1, 2015.

The CEO of The Heart Foundation (NSW), Kerry Doyle, said there are chemicals in e-cigarette vapours that the public should be protected from.

"The trouble with e-cigarettes is that we don't know what's in a lot of them," she said.

"What we do know is that in NSW a great proportion of the ones that were tested by our own health department actually had nicotine, which is a scheduled poison.

"So, of what we know, it's not good and the rest of it is unknown."

Ms Doyle said she had experienced the potentially harmful chemicals in e-cigarette vapours first hand.

"I had the not so pleasant experience of standing on a train station not so long ago next to a young lady who was on her e-cigarette and there was massive vapour around it," she said.

"In fact, it was like a small fire."

There have been calls for the Government to extend the bans on e-cigarettes to include all those applicable to tobacco.

However, Health Minister Jillian Skinner said she was not satisfied that is necessary.

"The jury is still out on whether there isn't some case for some electronic cigarettes, particularly those that have very low or no tobacco in them, as a potential harm minimisation or stop smoking aid," she said.

"But the jury is still out on that and we're waiting on the results of some of that research."

Ms Skinner said the progressive roll-out of the new rules would give businesses and consumers time to adjust.

"We want to allow for a public education campaign and for retailers to prepare for advertising and display requirements," she said.

"That's something we always try to work with businesses to make sure they understand their new obligations and get those into place."