I work in an office building. Smoking is prohibited throughout the entire building, as well as in outdoor spaces within a certain distance from the entrance. Some of my coworkers who smoke have taken to using e-cigarettes, as a way to reduce the health risks associated with smoking. Winter is coming, though, and they want to use their e-cigarettes indoors. A bunch of us are worried about the health effects of second-hand "vapor," and we want our company to treat e-cigarettes like regular cigarettes. Does the law allow our employer to ban e-cigarettes just like all other smoking products, or are they in some special category?
Because e-cigarettes are relatively new, there are still some questions about how employers may treat them. Only a few states have passed laws that explicitly address e-cigarettes in smoke-free venues. In North Dakota, New Jersey, and Utah, e-cigarettes are treated just like other tobacco products. (Utah's law includes an exception allowing people to "vape" in establishments that sell e-cigarettes.) A number of other states have passed laws that prohibit smoking (including e-cigarettes) in specific establishments, such as schools, correctional facilities, and sports arenas.
In other states, it's not clear whether the state's general laws on smoking in indoor workspaces also encompass "vaping." However, many cities and local governments have passed laws specifically addressing e-cigarettes. Under these laws, using e-cigarettes is treated like "smoking" for purposes of the area's smoking prohibitions. Some laws allow e-cigarettes to be used in more places than regular cigarettes, however. (For a complete list, along with detailed information on e-cigarettes, check out the e-cigarettes page at the website of the American Nonsmokers' Rights Foundation.)
If your state or local government has no law dealing with e-cigarettes, your employer is most likely free to decide whether or not to prohibit them at work. Employers are generally free to adopt reasonable policies on what employees may and may not do at work, including dress requirements, codes of conduct, and so on. In fact, because the health risks of second-hand vapor are not yet known, a workplace ban may be the safest legal course of action.