Tehran University of Medical Sciences International Journal of Occupational Hygiene 2008-5109 4 1 2015 10 11 47 52 EN MAHMOUD MOHAMMADYAN Health Sciences Research Center, Faculty of Health, Mazandaran University of Medical Sciences, Sari, Iran. YASER BAHARFAR Department of Environment and Energy, Science and Research Branch, Islamic Azad University, Tehran, Iran. 2015 10 10 2015 10 10 This study was carried out to evaluate tobacco dust concentration and also designing a suitable ventilation system for reduction of tobacco dust concentration in a tobacco processing factory in the north of Iran.Gravimetric method was used to determine the tobacco dust concentrations in the emission sources an also indoor workplace. A local exhaust ventilation system was designed according to the velocity pressure method recommended by ACGIH. Mean tobacco dust concentrations (ranged from 23.56 to 432.59 μgm-3) were higher than TLV-TWA in the proximity of all indoor emission sources where some individuals were working. However, mean indoor and outdoor tobacco dust concentrations (7.71and 0.04 μgm-3 respectively) were lower than TLV-TWA. Totally 5 separated ventilation systems and 5 centrifugal fans were designed and selcted to pull the air through 46 different hoods. Some downward slot hoods similar to VS-708 type were designed for the work-tables in tipping unit and some upward slot hoods that are similar to VS-903 type recommended by ACGIH's industrial ventilation committee were also selected for tipping manipulation unit. Some enclosing hoods were designed for feeders. Duct velocity of 1060 mmin-1 has been selected for all systems. Total air flow rates ranged from 240-369 m3min-1. A very high efficient bag house containing several bag filters was used to collect dust. In conclusion, because of a high concentartion of tobacco dust in the proximity of sources and risk of workers exposure to tobacco dust, a suitable local exhaust ventilation system was designed to reduce particulate air pollution concentrations in a tobacco processing factory. https://ijoh.tums.ac.ir/index.php/ijoh/article/view/48 https://ijoh.tums.ac.ir/index.php/ijoh/article/download/48/48