Tehran University of Medical Sciences International Journal of Occupational Hygiene 2008-5109 10 3 2018 08 30 158 164 RASOUL YARAHMADI Occupational Health Research Center, Department of Occupational Health, School of public Health, Iran University of medical sciences, Tehran, Iran MITRA RASHIDI M.Sc. Student, in Occupational Health, Tehran University of Medical Sciences, Tehran, Iran ALIREZA ALIPOOR Assistant Professor of Mechanical Engineering, Sahid Chamran Ahvaz University, Ahvaz, Iran PARVIN MORIDI Air Pollution Research Core, Pars Plasma Bonyan (knowledge based Co), Tehran, Iran. 2019 02 27 2020 01 19 Reported exposures to hazardous fumes and gases from the welding process indicate the importance of using effective ventilation systems to control these emissions. This study was designated to control the welding contaminants and to utilize the performance of a prototype on-gun system in bench scale. The study evaluated ventilation parameters including exhaust flow rate, capture velocity, and lastly, duct and face velocities for the system of interest. Hood operation was tested at 34.06 standard cubic feet per minute (SCFM). ISO 10882-1 (part 1) method, the gravimetric method, was used to determine the total particle concentration and hood efficiency.  The study found that, in general, when the hood face was located at 2 cm from the gas nozzle, capture velocity in arc point reached 140 fpm. By increasing the distance to 4-6 cm, the capture velocity decreased to 100 and 60 fpm, respectively. We concluded that the distance of the hood face from nozzle had a direct effect on capture efficiency. The evaluated hood could reduce exposure risk of welding fumes with a capture efficiency of 77.73% in the hood distance of 2 cm from the nozzle. https://ijoh.tums.ac.ir/index.php/ijoh/article/view/382