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Indoor air purification is extremely urgent to eliminate the health threat of PM 2.5, VOCs and microbial aerosol for exposing people, for which ESPs enjoy exceptional advantage for its special high-voltage characteristic. However, the secondary air pollutant of ozone is produced to possibly cause potential risk. In this work, six kinds of two-stage ESPs containing various charger and collector units, whose structure and size design are determined according to the indoor application, are developed to investigate the comprehensive control of PM 2.5 capture and ozone emission. Responsive surface methodology is employed to explore the relationship among ozone concentration, wire number, charger current and airflow velocity, and obtain regression model for predicting ozone emission. The comprehensive evaluation standard considering efficiency-ozone double factors is proposed to optimize structure design and working conditions of two-stage ESPs. Experimental results show that two-stage ESPs with a unit ratio of >3/4 can keep relatively good stable state, whose current reduction is in around 10 μA, for preventing particle charging function of charger from basically affecting. For the two-stage ESP with Ra = 2/5, it finds the optimization of working conditions of collector can bring rapid improvement of collection efficiency for 0.25 μm particles, which reaches up to be >60 %, while the optimization of that of the charger can only result in an enhancement of <30 %. RSM analysis exhibits a strong connection between the interactive effect of charger current and airflow velocity for presenting a steep response surface. Based on comprehensive control of PM 2.5 and ozone pollutants, it suggests the two-stage ESP with Ra = 2/5 is selected at the first priority and then that with Ra = 1/6, while two-stage ESP with Ra = 4/3 is not recommended for unsatisfied consequence of both of PM 2.5 capture and ozone emission., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The high-voltage electric field can effectively capture charged aerosols and has the effect of killing microbial aerosols simultaneously. In this article, an innovative visualization method for investigating the dynamic characteristic of submicron-scale aerosol particles in the high-voltage electric field is developed. Based on reasonable working principles and reliable experimental schemes, the movement of submicron-scale aerosol particles is observed and visualization images in different working conditions are photographed. Besides, with the aid of numerical method and solution of related equations, simulation researches on flow field distribution, electrostatic field characteristics, particle charging and motion behavior characteristics are also carried out. Visualization results prove the linear motion law of aerosol particles in an electric field of 0-3 kV/cm unit. As for 1 µm diameter particle, its migration velocity in 1 kV/cm electric field is measured as 0.016 m/s and 0.019 m/s after positive and negative charging of 1.5 kV voltage, respectively. A reliable calculation formula (η=(V j q p L j )/(3πμD 2 u x d p )) for predicting collection efficiency is derived and established based on actual particle migration velocity. The researches on the migration and capture law of submicron-scale aerosol in the high voltage electric field gives a key reference for the development and design of efficient removal of microbial aerosol and air purification equipment., (Copyright © 2021 Elsevier B.V. All rights reserved.)