Gregory Conley can't go inside his favorite Starbucks in Mount Laurel to take a few puffs, so he enjoys his habit outside. To passersby, it may look like he is drawing deeply from any old cigarette, but a closer whiff proves otherwise.

That's because the newest smoking rage, boosted by "vapers" (that's with an e, not an o), is not to smoke - sort of.

Battery-powered "e-cigarettes" - no matches needed - give consumers a nicotine fix without the burning tobacco haze, hazards, and stench of their old-fashioned counterparts. The number of vapers - estimated at 3 million - is growing with such celebrities in their ranks as actress Katherine Heigl (she vaped on the Late Show With David Letterman) and ex-ballplayer Jose Canseco.

Even Charlie Sheen is part of the e-smokeless parade, reportedly signing on as a partner with NicoSheen, a line of disposable e-cigs and related products.

Last month, vaping advocates celebrated removing a big, bureaucratic obstacle when the U.S. Food and Drug Administration said it would regulate e-cigarettes as tobacco products. The announcement came after a federal Court of Appeals ruled the agency could not treat them as it had been doing, as medical devices, based on the industry's marketing claims that e-cigs are smoking-cessation aids. The FDA had been blocking their importation.

E-cigarettes are illegal in some countries, including Australia, Singapore, and Brazil. Pennsylvania and most other states do not have laws restricting them, though last year New Jersey prohibited e-cig sales to minors and included them in its indoor smoking bans.

That's why Conley, a 24-year-old Rutgers-Camden law and business student, has to sit outside to savor his e-cigarette along with the victory over the FDA.

"Thankfully, we've won a majority of battles," says the ex-smoker, who handles legislative affairs for the Alabama-based activist group Consumer Advocates for Smoke-free Alternatives Association.

Where there are activists, there are controversies, and the air around e-cigs is thick with all sorts of disputed facts and friction, including whether they are effective nicotine replacement therapies like the patch, or - with flavors ranging from banana split to bacon - whether they entice young people who never have smoked.

Most e-cigarettes, made of plastic or metal, consist of three pieces: a disposable cartridge for liquid nicotine, flavorings and other compounds; an atomizer with a heater that turns the liquid to vapor; and a battery. A light on the tip even glows like a real cigarette.

Upon inhalation, the nicotine-charged mist simulates the sensation of smoking, vapers say, making it an easy transition for people looking to quit the real deal.

Until more is known about e-cigarettes, first marketed in China in 2003, public health experts say the wisest approach is caution.

"The exposure of the brain to nicotine can be very powerful and it can cause changes which are long-lasting," says Jonathan Winickoff, an associate professor of pediatrics at MassGeneral Hospital for Children who studies pediatric tobacco control. "We need to make sure we can protect children from it."

Most e-cigarettes are sold online, though one brand, NJOY, is available for $19.99 at some 7-Elevens in the Philadelphia area. A titanium e-cigarette billing itself online as "The Big Hitter! Huge mouthfuls of vapor" starts at $169.99.

Online retailer ecigg, which sells a basic starter kit for under $40 that includes atomizers, batteries, and prefilled cartridges, has its warehouse in Roxborough.

"Per month, we do between $10,000 and $20,000 in sales," says president John Poole. Sales jumped in January because of New Year's resolutions to quit smoking, he says.

Jeffrey Turse, a 32-year-old patrolman with the Hazleton, Pa., Police Department, has smoked tobacco cigarettes since he was about 14, trying several times unsuccessfully to quit. Yet ever since he tried e-cigarettes in 2009, he says, he hasn't smoked a real cigarette.

These days, Turse considers vaping a hobby, not a habit. In March, a Philadelphia meet-up he attended put on by the National Vapers Club attracted 242 people. The club began as a social group for e-cigarette aficionados, but has grown to prevent bans and promote vaping at events like the Midwest Vapefest.

The reaction of non-vapers, which describes most of Turse's fellow police officers, is a different matter.

"They actually laugh about it," he says, and they jokingly ask whether he's smoking something legal.

Their nickname for him? "Hookah Boy," Turse says, referring to the contraption also known as a water pipe.

In many ways, vapers may be a subculture. One 2010 survey of 2,217 vapers by the smoke-free alternatives association showed them to be overwhelmingly over 30, mostly men, mostly white. About 70 percent have attended some college or earned a degree; two-thirds smoked for more than 10 years. They definitely are a group defined, in part, by whom they view as friend and whom they see as foe.

Friends, including the American Association of Public Health Physicians, consider e-cigarettes a safer alternative to tobacco, which contains more than 7,000 chemicals, hundreds of which are toxic and about 70 of which can cause cancer, according to the Centers for Disease Control and Prevention. Bill Godshall, executive director of SmokeFree Pennsylvania and a longtime campaigner for smoking bans in public places, theorizes that e-cigs are "at least 99 percent less hazardous than cigarettes and there's no smoke, so nonsmokers don't get harmed."

Critics, including the FDA and the American Cancer Society, see e-cigs as having some toxic properties and risky until proved benign.

"We hope research will move quickly to determine if these devices are safe or are helpful in quitting smoking," says a cancer society spokeswoman. "Until the evidence is there, we will continue to recommend that smokers use FDA-approved methods proven to help smokers quit successfully."

Then there are people outside of the public kerfuffle, like Frank Leone, director of the Comprehensive Smoking Treatment Program at the University of Pennsylvania.

"The real question is not whether e-cigarettes are better than cigarettes. The question is whether e-cigarettes are better than treatment - real treatment," he says.

Some worry that e-cigarettes could be a distraction for people who otherwise would quit smoking entirely, or could be an easy gateway to tobacco for youngsters.

Nicotine alone is still "a fairly strong toxin to the nervous system," said Thomas Gould, a psychology professor and expert in the neurology of addictions at Temple University. Many retail e-cig websites have no safeguard against minors making purchases other than to ask visitors to confirm they are 18 or older.

Amid the haze, there's one point on which most everyone agrees. Says Leone: "I guess it's safe to say that anything is healthier than cigarettes."

Contact staff writer Carolyn Davis at 215-854-4214, cdavis@phillynews.com, or twitter.com/carolyntweets.