With the increasingly serious air pollution, it is urgent to build a good indoor environment. How to improve performance of filter fiber materials has become the mainstream approach. In this article, the structure and filtration performances of nonwoven filter fibers before and after impregnation with carbon black were tested and analyzed. The results showed that a carbon black coating layer was wrapped on the surfaces of the changed nonwoven fabric filter fibers. The porosity of fibers decreased from 97.81% to 95.35%. The filtration efficiency of PM1.0, PM2.5, and PM10 increased by 16.8%, 28.0%, and 11.7%, respectively, at the best filtration velocity of 0.8 m/s. The filtration efficiency of PM2.5 had the most significant improvement. But the resistance increased by 1.18 times at the same time. The matching between filtration efficiency and resistance should be considered in using. This study provides reference value for the synthesis and application of new filter materials.

The filtration performance of four kinds of coarse polyester filters commonly used in the market was studied experimentally. The results showed that these filter materials had better filtration efficiency for particles larger than 5 μm. There was a significant difference among the same grade filters on filtration efficiency and resistance. The maximum counting efficiency of all four Samples can be achieved when the filtration velocity was 1.1 m/s. Fiber diameter was one of the main influencing factors that affect the efficiency and resistance of polyester filters. The comprehensive effect was relatively good when the Sample fiber diameter was small.

Experiments and theoretical analyses are conducted in a residential building in Changzhou to study indoor PM2.5 concentrations by establishing a combined parameter model. An alternative method for predicting the particle deposition rate and penetration coefficient is proposed, and its accuracy is tested and verified by experiments using time-dependent concentrations and air exchange rate measurements. The predicted PM2.5 penetration coefficient increased from 0.70 to 0.88 when the air exchange rates were varied from 0.2 h−1 to 0.5 h−1. In addition, outdoor sources of PM2.5 dominantly contributed approximately 90% to 98% to the indoor concentrations for both mechanically and naturally ventilated structures. Finally, a mathematical model for predicting the indoor concentration is presented using a mass balance equation, which estimates the parameter values in the building. The indoor PM2.5 concentrations ranged from 40 to 46 µg/m3 by using a fresh air system with 82% filtration efficiency, while those by using open windows for natural ventilation ranged from 105 to 118 µg/m3 when the outdoor PM2.5 concentration ranged from 115 to 137 µg/m3. The results of this study can be used to estimate the indoor particle level. Practical application: By applying the ventilation criteria for acceptable indoor air quality in ASHRAE Standard 62.1, the indoor PM2.5 monitoring results show serious pollution in dwellings in 2018. More dwellings are expected to maintain a clean indoor environment in the future. Thus, it is crucial to consider the indoor PM2.5 pollution risk in the building design to prevent the possible consequences of unsafe high indoor concentrations. The use of this prediction model, as discussed in this article, will provide further information on the influence of the particle deposition rate ( K) and penetration coefficient ( P) on indoor PM2.5 concentrations.

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