If you are based in the US, it may depend on where you are currently located, you see
The Food and Drug Administration (FDA) classified electronic cigarettes as drug delivery devices and subject to regulation under the Food, Drug, and Cosmetic Act (FDCA) prior to importation to and sale in the United States
As quoted from Link hidden: Login to view
There is an argument going on in many states regarding how the e-cigarette and its components are to be classified. It would be best if you check with your local registry.
I think you might find this forum mighty helpful in your business - Link hidden: Login to view
Hope this helps :) All the best!