Talia Eisenberg, co-founder of the Henley Vaporium, uses her vaping device in New York. (AP Photo/Frank Franklin II)

The Food and Drug Administration announced Thursday that it would move to regulate e-cigarettes, which have quickly grown into a $2 billion a year enterprise. Some things you should know about "vaping."

How they work: Most consist of  a rechargeable, battery-operated heating element, a replaceable cartridge that contains nicotine or other chemicals and an atomizer that, when heated, converts the liquid in the cartridge into a vapor. This vapor is inhaled. Nicotine concentrations vary depending on the user's preference.

• E-cig manufacturers claim that they are significantly less expensive than tobacco cigarettes, which are heavily taxed.

• Right now, makers of e-cig products don't have to disclose their ingredients. A UC San Francisco researcher claims that 10 chemicals on California's annual list of known carcinogens can be found in e-cig vapor, including benzene, formaldehyde, lead and toluene. The liquids come in flavors such as watermelon and bubblegum.

• A Syracuse hospital banned the devices after a patient using oxygen caught fire while smoking an e-cigarette. The FDA has reported four fires connected to the devices.

• The percentage of U.S. high school students who have tried vaping doubled from 2011 to 2012, according to the Centers for Disease Control and Prevention. Ten percent say they've tried an e-cigarette.

• Calls to poison centers around the U.S. have risen from about one per month in September 2010 to 215 per month in February of this year, according to the CDC.

• Cities across the country have moved to ban e-cigs in many of the same places that tobacco is prohibited. But vaping lounges have sprung up as places for people try the devices and continue to use them. Some aficionados blame "cloud chasers" -- newer participants who intentionally blow large, billowing fogs of vapor--for vapers' negative image.