Is e-cigarette really safe?

Electronic cigarettes or e-cigarettes might be heaven-sent for those who want to quit smoking. Because it’s like giving them the satisfaction of smoking without the harmful side effects. Did you know that smoking is now allowed in malls? Well, that’s if you’re using an e cigarette. I also got surprised when I saw someone “smoking” and found that he’s holding an e-cigarette.

Now, with the e cigarette becoming popular, I’m just curious if it’s really safe? And what about other people beside the users who inhaled the smokes? Does second-hand smoke also applies with e cigarettes?