Procedures
Participants visited the lab twice and were asked to refrain from smoking, eating food, drinking alcohol, or using the lavatory from one hour before each lab visit. After taking consent, participants completed a baseline questionnaire to assess socio-demographics, smoking-related characteristics and psychopharmacological outcomes. They then provided breath and urine samples for toxicological analysis. Following sample collection, participants were walked to an outside area and asked to use either a NVP or an HTP, provided by the study team, for 5 min. No specific instructions were given to participants about how to use the product in these 5 min, apart from how to switch it on and off. After product use, participants completed a follow-up questionnaire to assess psychopharmacological outcomes. At the second visit, participants again completed a baseline questionnaire on psychopharmacological outcomes, tried the other product, and completed a follow-up questionnaire to assess psychopharmacological outcomes after product use. The order of product use was randomised to account for sequence effects. Excel random number generator function was used to randomise the participants to which product they used first and which one second.