Today is the first day that the indoor e-cigarette ban will be put into motion in Chicago, one of several cities taking steps to subject vaping to the same regulations as tobacco and hoping to curb e-cigarette use in public places.

Chicago’s new rule, which will prohibit people from vaping in restaurants, bars, and other indoor public places, was passed by the City Council in January. Chicago Mayor Rahm Emanuel urged the passing of the rules due to his belief that e-cigarettes are “gateway drugs” of sorts, likely to lure the younger demographic to tobacco.

Recently, the Food and Drug Administration announced that it would put more effort into regulating e-cigarettes, by banning minors and monitoring vaping manufacturers, requiring them to place health warnings on their labels. The FDA announcement came on the heels of a Centers for Disease Control and Prevention (CDC) report that boldly declared e-cigarettes are “poisoning” children.

Advocates of the new ban believe that though e-cigarettes may be the lesser of two evils, they can still cause harm — especially since many of the chemicals produced by vaping haven’t been properly examined yet. “Imagine for a moment you’re at a bar and there are 20 people who are puffing on something that looks like a cigarette and then somebody smells something that smells like tobacco smoke,” Dr. Thomas Farley, the NYC health commissioner under former Mayor Michael Bloomberg, told The Associated Press. “How’s the bartender going to know who to tap on the shoulder and say, ‘Put that out’?”

Though scientists haven't fully examined all of the chemicals involved in vaping, they are worried about one thing for certain: the nicotine present in e-cigarettes can easily get people addicted. “They are nicotine delivery devices intended to be used like a cigarette,” Dr. Norman Edelman, chief medical officer at the American Lung Association, said. “What happens to someone who stops inhaling the tars of cigarettes and inhales only nicotine? We don’t know. There is at least the potential for harm.”

Proponents of e-cigarettes, however, are frustrated, saying the new regulations will make it even harder for smokers to quit tobacco. “The tougher they’re going to make it on vapers, the tougher it is people are going to find an actual vehicle for quitting or as a supplement to cigarettes,” Chris Jely, 31, told the AP. “There’s no need for it. This is working so much better than patches or gum or prescription drugs.”