PRIMARY OBJECTIVE:~I. Study that flavors might be related to the phenomenon of 'indirect' toxicity.~OUTLINE: Participants are randomized to 1 of 2 conditions.~CONDITION I: Participants attend up to 3 video or telephone conferences over 2 hours each with a minimum of 24 hours and maximum of 1 week between sessions. Participants take a fixed number of puffs on 3 randomly assigned conditions (combinations of carrier and nicotine concentrations).~CONDITION II: Participants attend up to 2 video or telephone conferences over 2 hours each with a minimum of 24 hours and maximum of 1 week between sessions. Participants take a fixed number of puffs on a nicotine-free condition and 3 randomly assigned conditions (combinations of carrier concentration and nicotine form).
This trial aims to develop reliable and valid measures of sensory experiences unique to e-cigarette use. Regardless of whether flavorings show evidence of toxicity in a biological sense, they may nonetheless increase harm by other means, such as increasing appeal, decreasing risk perceptions, or masking harshness or irritation that might lead users to discontinue use.