FINE AND COARSE AEROSOL PARTICLES IN A STUDENT CLUB BEFORE AND AFTER A SMOKING BAN J. HOVORKA, M. BRANIŠ, P. GADAS, T. VALCHÁŘOVÁ Institute for Environmental Studies, Faculty of Science, Charles University in Prague, Benátská 2, Prague 2, , Czech Republic In contrast to USA and most of the EU countries, smoke-free restaurants, bars and cafes are still rare in the Czech Republic. However, stricter regulations have been recently applied to minimize adverse effects of smoking on human health. We took the opportunity of changes in the smoking rules on the university premises and performed two short campaigns to ascertain differences in aerosol mass-size concentrations in a students club “Dead Fish” at the Faculty of Science, Charles University - FSCU- in Prague. We hypothesized that smoking ban will have a significant effect on particle concentrations. Conclusions Diurnal variation of PM mass concentrations exhibited, during both campaigns, almost the same pattern corresponding to the presence of customers. Also the congruency of exponential decrease of PM 10 mass concentration after closing time at 2:30 AM indicated quite similar conditions of ventilation After the ban PM 10 concentrations decreased, on average, by 25% while PM 1 and PM 2.5 dropped by more than 50%. The proportion of PM 1 (PM 2.5 ) to PM 10 decreased from 57% (74%) to 38% (56%) between 2005 and 2006 respectively The mayor difference between before/after the smoking ban periods is disappearance of fine (0.6  m) particle mode. But true modality determination of this fine aerosol fraction is limited by the detection limits of the APS. Diurnal variation of PM 10, PM 1.0 and aerosol mass size distribution BEFORE SMOKING BAN in the bar Diurnal variation of PM 10, PM 1.0 and aerosol mass size distribution AFTER SMOKING BAN in the bar Diurnal variation of PM 1 (PM 2.5 ) exhibited near the same pattern in both 2005 and 2006 reflecting opening hours of the bar Higher decrease of relative and absolute PM 1 (PM 2.5 ) values in comparison to PM 10 mass concentrations agrees with changes in mass size distributions during opening hours. In 2005, left, mass size distributions were bi-modal with the first mode in the region of fine (GMD 0.6  m) particles and the second mode in the region of coarse (GMD 6  m) particles. Particles of the fine mode were apparently produced by smoking. They formed the majority of PM 1 and PM 2.5 masses. Termination of smoking resulted in a large drop of PM 1 and PM 2.5 mass concentrations. In 2006, the first (fine) mode disappeared and the recorded distributions became mono-modal (GMD 6  m) The mass concentrations of coarse particles (PM 10 – PM 1 ) did not change significantly because their principal source was most probably resuspension caused by movement of people, which contrary to smoking, has not changed compared to the before- ban period. Campaign medians of PM 10, PM 2.5 and PM 1 mass concentrations (  =1.5gcm -3 ) PM 1 /  g m PM 2.5 /  g m PM 10 /  g m Study objectives: T o quantify differences in the mass of particles of different sizes which are mostly affected by smoking ban Data: 5 min integrates of number size distribution,  m by Aerodynamic Particle Sizer (APS 3321,TSI) 5 min integrates of indoor/outdoor temperature and relative humidity 24 hour samples with 50% cut-points at 2.5 µm, 1.0 µm, 0.50 µm, 0.25 µm and <PM.25 by Sioutas Cascade Impactor (SKC) 30 min integrates of outdoor PM 10 data provided by fixed site monitor (TEOM) One campaign (6 days) was performed under “smoking regime” in the spring 2005, the second campaign (19 days) in winter 2006 after the ban Acknowledgement The research was carried out under the Institute for Environmental Studies of FSCU in Prague institutional support. Regular opening hours in the bar were in 2005 from 10 AM–2 AM next day while in 2006 opening hours started about one hour earlier. Number of customer present and activities, like candle/aromatic stick burning or water-pipe smoking were also recorded during the measurement period. There was not forced ventilation in work during the sampling campaign, so aerosol particles disappeared due to natural ventilation and by plateout on the bar surface.