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Under the goal of "achieving carbon peak by 2030 and carbon neutrality by 2060", how to select the type of fresh air system has become a key area of energy conservation. The method of outdoor design PM2.5 concentration is one of the important factors affecting the selection of fresh air filtration system. This paper first analyzed the PM2.5 concentration values of 31 cities in China from 2017 to 2020 based on mathematical induction, and next gave the recommended coefficient K under six urban economic regions methods in combination with the actual situation. Finally, the selection of air filters in five typical cities was taken as an example, the differences in recommended coefficient K and selection of outdoor design PM2.5 concentration under different recommended methods were compared and analyzed. The results showed that the recommended coefficient K under the six economic regions could meet the required K value needs of the region. The recommended coefficient K by the six economic regions methods based on per capita GDP is the best. Under that conditions, the recommended coefficient K of the five typical cities under strict and normal conditions differs from the average K values of the six methods by 0.06 and 0.04. This paper will provide a new method for the correct selection of outdoor design PM2.5 concentration in fresh air systems to achieve the dual carbon energy-saving goal. [ABSTRACT FROM AUTHOR]

To protect occupants in vehicle cabin environments from the health risks of high concentrations of particulate matter (PM), it is important to install vehicle cabin air filter (VCAF) to eliminate PM. In this study, we investigated the filtration performance of 22 VCAFs. Results showed that the minimum average filtration efficiency was 56.1 % for particles with a diameter of 0.1-0.3 μm, a pressure drop of 33.2-250 Pa at air velocity of 2.5 m/s, and the dust-holding capacity ranged from 5.8 to 19.4 g. In addition, as the filter area increased from 0.23 m 2 to 0.50 m 2 , the filtration efficiency for particles with a diameter of 0.1-0.3 μm increased from 56.7 % to 77.5 %, the pressure drop decreased from 96.1 to 62.5 Pa, and the dust holding capacity increased 2.7 times. Furthermore, we compared the service life of VCAF from 31 major Chinese cities and found that the service life varied greatly from maximum of 1730 h for Haikou to minimum of 352 h for Shijiazhuang. Considering occupant health risks, Beijing requires that VCAFs have PM 2.5 filtration efficiency at least 88.1 %, and Liaoning requires minimum of 97.5 %. Hence, choosing the appropriate VCAF based on the atmospheric environment of different cities deserves our attention., 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 © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

With the increasing popularity of fresh-air filtration systems, the methods of determining the outdoor PM 2.5 design concentration have become more important. However, the monitoring of atmospheric fine particles in China started relatively late, and there are relatively few cities with complete data, with obvious regional differences, which led to many problems in the selection of air filters for fresh-air filtration systems. In this paper, three methods of determining outdoor PM 2.5 design concentration were analyzed using the daily average concentration of PM 2.5 in 31 provincial capital cities from 2016 to 2020. Six typical cities in different regions were also taken as examples. The advantages and disadvantages of the three existing statistical methods were compared and analyzed, as well as the corresponding differences in the selection of outdoor PM 2.5 concentration value on the filter systems. The results showed that the method of mathematical induction was more accurate and reasonable for the calculation of outdoor PM 2.5 design concentrations. The local outdoor PM 2.5 design concentration could be quickly calculated using the recommended coefficient K and annual average PM 2.5 concentration of the region, especially for small and medium-sized cities without monitoring data. However, the recommended coefficient K should be provided based on the specific region, and should be divided into values for strict conditions and normal conditions during use. This would provide a simple and effective way to select the correct air filters for practical engineering.

PM2.5 is an important global air pollution issue. PM2.5 causes various problems on the environment and human health. Even though PM2.5 of the outdoor air is eliminated by particulate air filters, the chemicals adsorbed on the filtered PM2.5 can be outgassed and introduced into the semiconductor manufacturing facilities and processes, thus causing defects on the semiconductor chips by producing particles and haze as airborne molecular contamination. Therefore, estimating the amount of the outgassing from PM2.5 is a very important factor to control gaseous contaminants in the semiconductor industry. In this paper, the PM2.5 samples at different PM2.5 mass loadings were collected in Xi’an, China and evaluated using the soft X-ray radiolysis method for determining the relation between the outgassing and the PM2.5 mass loading. The PM2.5 samples were also analyzed by several methods for quantifying organic and elemental carbons, water soluble ions, and organic compounds in the PM2.5 samples. The outgassing measured by the soft X-ray method increased linearly with the PM2.5 mass loading, and the chemical analyses explained that the organic carbon (OC) was dominantly detected by the soft X-ray method in the current study. Moreover, the sampling location of the PM2.5 affected on the organic compounds of the PM2.5. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicle (UAV) has the advantages of flexibility, strong controllability, and easy deployment. It provides wireless communication with low delay and high throughput. However, under the background of the increasing shortage of spectrum resources, the frequency band resources of UAV systems are tight, resulting in increasingly serious co-channel interference between services, and the communication quality cannot be effectively guaranteed. Therefore, it is very important to evaluate the co-channel interference of UAV system and improve its spectral efficiency. This paper introduces the interference model for the research and analysis of the frequent coexistence of UAV and connected vehicles WLAN system and applies the model to evaluate the co-channel interference of UAV in the ISM frequency band of 2.4 GHz. The actual receiver filter is modeled and analyzed, the FDR mathematical expression for changing the protection band is derived, and two UAV interference signal waveforms, cyclic prefix orthogonal frequency division multiplexing waveform and windowed orthogonal frequency division multiplexing waveform, are proposed to effectively improve the utilization of frequency resources. After simulation, the interference of the interfered connected vehicles WLAN system is calculated and compared with the relevant service interference threshold standards issued by the International Telecommunication Union. To ensure that the UAV will not interfere with the connected vehicles WLAN system in the ISM frequency band of 2.4 GHz, the protection height of the UAV system in China is 6.2 km. [ABSTRACT FROM AUTHOR]

Efficient filtration provides a healthy and comfortable residential environment. Based on the performance testing for filter materials commonly used in China, the mass balance equation of controlling the indoor PM2.5 concentration was set up, and the filter selection criterion was discussed. An optimal section was suggested by taking into account the economic cost, filter price, and indoor air quality. [ABSTRACT FROM AUTHOR]

In order to improve air quality, China has implemented a series of the most stringent control measures ever in recent years. Quantitatively analyzing the contribution of emissions to the trend change in air pollutants is an essential scientific basis for verifying the effectiveness of air pollution control. We based our study on the air quality online monitoring data and meteorological element data of 11 cities in the Fenwei Plain from 2018 to 2022. We quantitatively investigated the changing patterns of NO2, O3, PM10, and PM2.5 and their influencing factors in the major cities of the Fenwei Plain by using the KZ filtering and MLR modeling analysis methods. The results show the following: (1) The long-term fractions of NO2, PM10, and PM2.5 in the Fenwei Plain decreased by 10.5, 33.1, and 17.1 μg·m−3, with decreases of 25.8%, 29%, and 28.8%, respectively, from 2018 to 2022. The long-term fractions of O3 showed the characteristics of decreasing and then increasing, with 2020 as the dividing line. (2) The short-term components of NO2, PM10, and PM2.5 contributed the most to the total variance, with the proportion of short-term components ranging from 34.7% to 69.8%, 53% to 73%, and 43% to 58%, respectively. The seasonal components of O3 contributed the most to the total variance, with the proportion of short-term components ranging from 54% to 70.7%. (3) Most cities in the Fenwei Plain had unfavorable meteorological conditions with regard to NO2, PM10, and PM2.5 in 2018–2020 and favorable meteorological conditions in terms of NO2, PM10, and PM2.5 in 2020–2022. O3 showed different characteristics from the other three pollutants. Most cities in the Fenwei Plain had meteorological conditions in 2018–2019 that were unfavorable for improving O3 levels. In 2019–2021, meteorological conditions were favorable for improving O3 levels, while in 2021–2022, meteorological conditions were unfavorable for improving O3 levels. [ABSTRACT FROM AUTHOR]

In contrast to a majority of reported damage-cost literature being focused on outdoor pollution, this paper describes the development of a protocol that links population exposure data with reported epidemiological concentration-response coefficients. A change in indoor particulate level is expressed as a change in total exposure levels, which is then linked with a corresponding change in ambient particulate concentrations before evaluating the associated health benefits. In this study, the development of protocol is illustrated by using a typical office building environment and daily time activity patterns of office occupants in Hong Kong. Our results indicate that some benefit gains for the owners-employers and the society would be anticipated if certain filter set configurations had been adopted. However, the amount of benefit gains for the owners-employers is shown to be increased with the average salary level of employees and the duration of their stay in offices. [Copyright &y& Elsevier]

This research demonstrates the current use of air purification methods in the operating rooms (ORs) in China. 154 hospitals from 6 provinces were included in this survey to reflect the air purification methods of ORs in 2017. Air cleaning technology (ACT) is used in 124 (80.52%) hospitals. We find that the rates of using grade I, III, or IV clean operating room (COR) in tertiary hospitals are all higher than in lower level hospitals; the rate of using ACT in the ORs is higher, too. In addition, general hospitals have higher rate in using ACT in the ORs than specialized hospitals. The highest rate of using ACT in the ORs is in the eastern region of China. The number of hospitals using ACT, ultraviolet light disinfection, and air sterilizers (such as circulating air UV sterilizer) increased yearly. All grades of CORs can be maintained as required by more than 90% hospitals except grade II COR. In this research, we found air purification methods, especially the ACT, are widely used in hospitals' ORs. However, finding the way to select and use different air purification methods correctly is an urgent problem to be solved next. [ABSTRACT FROM AUTHOR]