Subjective effects assessment
At the end of each e-cigarette product use session (60 min relative to first puff), participants completed a single product liking questionnaire to evaluate the subjective effect of study product use. Answers were given by participants responding to the question “Can you tell me how much you like this nicotine product?” by making a vertical mark on a 100 mm horizontal line, with the boundaries set as “Very much” and “Not at all”. A product liking questionnaire was not completed for the usual brand cigarette product use session.