Abstract: Objective To study the level of fine particulate matter(PM_2.5) from smoking in public place and to evaluate the feasibility of PM_2.5 to be used as an index for monitoring smoking quantificationally.Methods TSI Sidepak AM510 was used to measure the concentration of PM_2.5 in four types of public place such as rest room in bath center,restaurant,karaoke bar,and cyber cafe in Tongzhou district,Beijing.The data was collected and the relation between smoking and indoor PM_2.5 concentration in public place was analyzed.Results The average concentration of indoor PM_2.5 in public places with and without smoking was 435.7±471.9,220.6±205.5μg/m³,respectively,and there was a significant difference between them(Z=-7.348,P<0.001).Furthermore,there were remarkable differences between the average concentration of indo or PM_2.5 of the different smoking levels(χ²=271.447,P<0.001).The average concentration of indoor PM_2.5 was positively related to the ratio of smokers(r=0.754,F=23.708,P<0.001).When ventilation(score≤2)was relatively bad,the average concentration of indoor PM_2.5 was 515.9±441.2μg/m³,and when the ventilation score >2,the concentration was 115.9±84.7μg/m³(Z=-19.791,P<0.001).The difference between them had statistical significance,and the difference was found both at places with and without smoking(P<0.001).Nomatter howthe ventilation was,the average concen trations of indo or PM_2.5 in the place with smoking were all obviously higher than that of without smoking(P<0.05).Conclusion Smoking could increase the concentration of indoor PM_2.5 in public places and the average concentration of PM_2.5 may reflectindo or air pollution from smoking in publicplace.