Laboratory and field investigation of portable air cleaners' long-term performance for particle removal to be published in: Building and environment

摘要

As an effective measure of improving indoor air quality, portable air cleaners (PACs) have been widely used in residential buildings to reduce indoor particle concentration. However, the air cleaner's filter performance may degrade over time during the dust loading process. In this study, the laboratory cumulate clean mass (CCM) tests, which are aimed to reflect the lifetime of the filter, were conducted with cigarette smoke challenging. Although the airflow rate decreased with the increased pressure drop, it was found that the reduced PAC's effectiveness was primarily caused by the significant decrease in single-pass efficiency after cigarette smoke loading in laboratory. The main reason was the elimination of electrostatic force by the organic matters contained in cigarette smoke, which was confirmed by the surface potential change after dust loading. Therefore, such test may not be truly representative of the ambient aerosol challenging in actual application. Long-term field monitoring of five PACs was then carried out in actual homes. Outdoor particle concentration greatly influences the field cumulate clean mass (CCMfield) through room infiltration. The decay rates of typical PAC's field clean air delivery rate (CADR(field)) versus CCMfield were obtained, ranging from 0.042 to 0.149%/(mg/m(2)). A new service life prediction method was proposed considering the decline of PAC's CADR(field) and the required CADR to keep indoor PM2.5 concentration below 25 mu g/m(3). In an archetypal case, if a PAC runs for 12 h per day, its service life is only about 1-3 months when outdoor average PM2.5 concentration ranges from 75 to 250 mu g/m(3).