Most people would be flabbergasted to see anyone smoking inside an office, a hospital waiting room or an airport. Yet, lately, people are smoking indoors — not traditional cigarettes, but e-cigarettes.

These are smokeless cigarettes that can look like the real thing, a pen or even a USB stick. What they all do is deliver nicotine to the smoker in a vapor form. A rechargeable battery powers a heating element that vaporizes the nicotine in a replaceable cartridge so that what's inhaled just looks like smoke.

Some e-cigarette companies claim the devices are safer and can help smokers quit. But critics say the companies' statements are unproven and their health claims are unsubstantiated.

It is true that e-cigarettes do not contain the over 4,000 chemical compounds created by a burning cigarette. Many of these are toxic and/or carcinogenic. Tar, carbon monoxide, nitrogen oxides, hydrogen cyanide and ammonia are all in regular cigarette smoke.

However, nicotine itself is dangerous and highly addictive, and with e-cigarettes, smokers may not know how much of it they're getting. A lack of regulation and quality control means the amount of nicotine in each drag of an e-cigarette is inconsistent. The U.S. Food and Drug Administration determined that since e-cigarettes are not considered a drug delivery device, the agency has no jurisdiction over them.

Yet the administration issued a health warning about e-cigarettes after its tests show they contain harmful chemicals such as diethylene glycol, a component of antifreeze that's toxic to humans and is banned in food and drugs. There were also detectable levels of a known carcinogen called nitrosamine and other toxic chemicals that users could potentially inhale.

Even if, as some enthusiasts claim, e-cigarettes can help a smoker quit, could it also entice young people to start? Health experts and the administration have both expressed concern e-cigarettes are marketed toward young people since the devices come in pink, gold or blue with flavors such as chocolate and bubble gum. Plus, the products' labels don't have a health warning.

Since e-cigarettes are unregulated and not covered by federal tobacco laws, they can be sold online and in mall kiosks. They're also cheaper than regular cigarettes. Because of this, they're easily accessible to children and young adults.

Some e-cigarette makers go so far as to make unsubstantiated health claims on their websites and printed materials. That's why Australia, Canada, Israel and Hong Kong have banned them on the grounds they have not been sufficiently tested for safety. New York City is pushing to become the first city to ban them.