Study On The Filtration Effectiveness Of Ventilation And Filtration System On Indoor Fine Particulate Matter(PM_2.5) Pollutants

With the development of economy,there is more serious atmospheric pollution in our country.Particulate matter pollutants such as PM_2.5 result in serious fog weather,which has serious impact on people's health.Building ventilation and filtration systems and the infiltration effect through cracks can bring such particulate contaminants into indoor environment.Also,in indoor environment,PM_2.5 generated by smoking and cooking can also have effects on the health of residents.Appling filters in ventilation systems or portable air cleaners in rooms is an effective method to clean air and protect residents'health.To assess the filtration effectiveness of the ventilation and filtration system,a new concept-integrated characteristic of filtration effect is needed.First,the long-term monitoring of building ventilation and filtration systems'filtration effectiveness on PM_2.5 were carried out in public buildings such as offices,airport terminal building,school classrooms,and in residential buildings.Field research results showed that ventilation and filtration system in many buildings have very low or even negative effectiveness on indoor PM_2.5.This indicated that the ventilation and filtration systems in buildings were unable to effectively remove indoor particulate pollutants due to a series of problems in design,operation and maintenance.On the opposite,they brought more PM_2.5 into indoor environment.Second,the influencing factors of filtration effectiveness were explored with the ideal single-zone model,the multi-zone model with uniform indoor source and the multi-zone model with non-uniform indoor source,respectively.For the ideal single-zone model,the filtration effectiveness of ventilation and filtration system was positively correlated with the clean air delivery rate,which in turn can be derived from a positive correlation with the air exchange efficiency₍?6?.The concept of air exchange efficiency was extended to other ventilation and filtration systems.The calculation formula of clean air delivery rate and the calculation formula of clean air energy efficiency ratio for fresh air system and circulating air system were given.For the non-ideal multi-zone models,the relationships between the filtration effectiveness and the air exchange efficiency₍?6? as well as the pollutant removal effectiveness?were established by the method of multiple regression analysis.Third,aiming at the problems existing in the current ventilation and filtration systems found in the field research,and guiding by theoretical models and conclusions,the improvement strategies of ventilation and filtration systems in office buildings were proposed.The modified ventilation and filtration systems has significantly increased the filtration effectiveness.Finally,ventilation and filtration systems'filtration effectiveness on the personal passive settling exposure was studied by using fluorescent particle labeling technology.There was a significant linear relationship between the initiative inhalation exposure reduction ratio and the passive settling exposure reduction ratio under different conditions.This indicated that the previous analysis on the effectiveness of the ventilation and air filtration system for initiative inhalation exposure can also be applicable to passive settling exposure.An accurate relationship between passive settling exposure and active inhalation exposure of particulate matter was given.