Heated tobacco products potentially reduces the risks of nicotine use. With most of the research on heated tobacco products (also known as “heat-not-burn” tobacco products) focusing on mainstream smoke, data on second-hand smoke has been limited to several chamber studies, and the effect on the indoor air quality in real-world settings has not yet been reported. Consequently, in this work, we assessed the pollution generated by a tobacco heating system (THS) in a hospitality venue. Volunteers used the THS in a nightclub during non-operating hours. Additionally, the indoor air quality of the club was evaluated during operating hours. The real-time aerosol particle concentration and the off-line carbonyl, nicotine and 3-ethenylpyridine concentrations were measured. The observed particle number concentrations were 1E+4, 5E+4, 1E+5 and 1E+6 to 1E+7 # cm–3 for the background, 10 users, 30 users and the club during operation, respectively, representing an increase by an order of magnitude for each subsequent scenario. The club featured relatively high background concentrations of gaseous pollutants, presumably due to third-hand smoke, and using the THS in the club during non-operating hours did not significantly affect the majority of these concentrations, with nicotine being an exception. Despite the increase in the background particle number and mass concentrations due to THS use, these values were still an order of magnitude lower than during operating hours.