Puff Topography and Sensory Effects Across IQOS Device Generations

The goal of this clinical trial is to learn how people use two generations of IQOS heated tobacco devices and how each device affects their smoking behavior and sensory experience. The main questions it aims to answer are: * Do participants puff differently when using the newer IQOS Iluma i compared to the older IQOS 2.4? * Does the flavor of the tobacco stick (preferred flavor vs. standard tobacco flavor) affect puffing behavior or sensory experience? * What are the differences in throat hit, mouthfeel, and satisfaction between the two devices? Participants will: * Attend 2 laboratory visits at the American University of Beirut * Use both the IQOS Iluma i and IQOS 2.4 devices during each visit * Have their puffing behavior recorded automatically during device use * Provide a breath sample before and after each use session * Complete short questionnaires about how each device felt and their urge to smoke

Inclusion Criteria: * Current IQOS user (at least 3 days per week in the past 30 days) * Age 18 to 65 years * Generally healthy * Willing to provide informed written consent * Willing to attend all laboratory visits * Willing to abstain from all nicotine and tobacco products for at least 12 hours before each visit Exclusion Criteria: * Use of any tobacco products other than IQOS in the past 30 days * Chronic cardiovascular conditions, seizures, or abnormal blood pressure * Current psychiatric disorder requiring active treatment, including major depressive disorder * Regular use of prescription medications that may influence cardiovascular function, respiratory function, or nicotine metabolism (excluding vitamins or birth control) * Use of cocaine, opioids, benzodiazepines, or methamphetamines in the past month * Marijuana use on more than 15 days per month * Current pregnancy or breastfeeding * Plans to quit nicotine or tobacco products within the next 30 days