On the wall of Paul Clift-Lands's cafe is a photograph of an oil painting. Painted in 1859, it depicts his great-grandmother as a small girl standing next to some vivid red-and-white flowers. The colours employed by the artist are more vivid in the photograph than in the original. The camera flash penetrated the painting's thick yellow patina caused by exposure to more than a century of tobacco smoke.

Enjoying a well-earned break in the lull before the lunchtime rush last Thursday morning, Clift-Lands shakes his head as he recalls an era when smoking was the norm. "People forget what it was like in the 60s. You'd walk into any pub and you'd be hit by the fug."

Not any more. Smoking is on the way out, especially among the young. New figures reveal that only 3% of 11- to 15-year-olds in England regularly smoke, compared with 9% a decade ago.

Experts say the smoking ban has been crucial in denormalising tobacco use, but Clift-Lands believes his Vaping Cafe in genteel Tunbridge Wells, the first in the country when it opened last year, is playing its part. The impressive array of e-cigarettes and vaporisers – the battery-powered gadgets that deliver nicotine in bursts of different flavours via atomisers – that are on sale in his shop are helping an increasing number of smokers to quit lighting up.

According to the health charity Ash, use of electronic cigarettes among adults has tripled in Britain from an estimated 700,000 users in 2012 to 2.1 million in 2014. The fledgling industry has already cemented itself into the zeitgeist. Everyone from Kevin Spacey's character in the US political drama, House of Cards, to Cara Delevingne, Johnny Depp, Snoop Dogg and dancers in a recent Lily Allen video enjoy vaping.

But this brings fresh concerns. Some experts fear vaping will introduce children to smoking. In addition, they fear that people who would never smoke are being encouraged to cultivate an addiction to nicotine, one of the most poisonous substances on the planet. A lack of hard data makes drawing conclusions difficult. The British Medical Association stresses the need for further research, saying that "it's really important that we find out if the hand-to-mouth use of e-cigarettes either breaks or reinforces smoking behaviours".

However, Deborah Arnott, chief executive of the health charity Ash, said the new figures showing the decline in smoking among young people should assuage these concerns. "Some people have been worried that electronic cigarettes could be a gateway into smoking for young people," Arnott said. "The latest figures show this has not happened so far. But we need to keep monitoring use in young people and make sure advertising and promotion of electronic cigarettes doesn't glamorise their use."

After a year behind his counter, Clift-Lands, 52, a reformed smoker who started smoking at age nine, has reached his own verdict. "I walk down the street and I see kids smoking cigarettes. It's a rite of passage. Nobody I know has gone from vaping to cigarettes. If it wasn't available, kids would be on cigarettes inhaling all the 70-odd carcinogens and everything else that comes with them."

As he says this, two suspiciously young lads walk into his coffee shop. Clift-Lands, who spent decades with the Metropolitan police, asks them for ID, although there is no minimum age requirement for the purchase of e-cigarettes. One of the boys explains that he is a smoker trying to give up. The other, who doesn't smoke, explains: "All my friends smoke. I don't want to smoke but I want to fit in." Do girls of their age vape? "No, it's more boys. The girls like to smoke."

The boy hands over £40 in cash and receives a bewildering amount of liquids, batteries, chargers and other paraphernalia that enable him to start vaping, or "grazing" as true aficionados call the act of inhaling vaporised nicotine. It seems like a lot of money, but someone with a 20-a-day habit will need to spend just £6 a week if they switch to vaping – considerably less than the price of one packet of 20 cigarettes.

"Parents drag their children down here when they find out they've started smoking," Clift-Lands says. He gestures at a whiteboard displaying prices and strengths. "They'd rather they did this than smoke."

Andrew Davis, a barista and musician, comes in to stock up ahead of his holiday to Turkey. He orders blueberry, vanilla, banana and grape flavours. "Newbies struggle," Clift-Lands admits. "There's too much choice. I try to restrict it. I offer around 25 flavours, but I could offer 50."

The shop, close to a mosque, does a good trade with local Muslims who particularly like the apple flavour. Clift-Lands favours the espresso flavour first thing in the morning. He tried chocolate, but few of his regulars cared for it. Cinnamon is popular at Christmas. Many people like to mix their flavours to create their own vape cocktail.

Davis, 31, credits vaping with him stopping his 10-a-day cigarette addiction. Like everyone who comes into the shop, he prefers the vaporisers rather than e-cigarettes, the devices that look like cigarettes but offer only three flavours. In the increasingly complicated – not to mention nuanced – world of vaping, e-cigarettes are very much the Betamax video, it seems.

"It's to do with the effect," Davis explains enthusiastically. "With vaporisers it's much more like the type of hit you get with a cigarette."

There are concerns that insufficient research has been done into the side-effects of vaping, especially the potentially harmful properties of glycol, a bonding agent used in the vaporisation process. "One of my regular clients is a doctor," Clift-Lands says. "He says even if there is something nasty in it, it's not going to be as bad as cigarettes."

He has a lot of customers in their sixties, keen to give up smoking. Many are now regulars. He started off making around £300 a week and now takes more than £1,000. It's not bad going for a small shop on an unloved road a little way from the town centre.

This success has not gone unnoticed. Over the road from the Vaping Café stands Totally Wicked, a vaping franchise imported from the US which has stores throughout the south-east. Vaping cafés are mushrooming across the UK. There is a land grab taking place analogous to the coffee shop market, where big high-street brands buy up premises close to established independent cafés. Clift-Lands says that he receives around 15 emails a day from people around the world trying to sell him products. He buys only from UK distributors whose product has been batch-tested by trading standards.

The market, he feels, is too fragmented. There are too many vaping devices using different chargers and batteries. Below his counter sits a sizeable electronic shisha pipe and a luxury wooden vaporiser resplendent in an attractive presentation box. They are examples of a fast-developing market, one that has caught big tobacco napping. The established cigarette giants have scrambled to launch their own vaping brands, fearful that they are going to lose millions of customers.

But the rapid rise of vaping could also be to its detriment. The Treasury would be concerned if e-cigarettes cannibalised its tobacco revenues. Clift-Lands grazes on his vaporiser and nods outside at the sign saying "try for free". He exhales a short, sweet burst of vapour and shrugs. "I give it two years before they come for us."