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Introduction: Air flow driven by air-conditioner has a significant impact on the indoor environment, however, the bacterial contamination conditions in the different parts of air-conditioners have not been fully elucidated. Methods: In this study, we assessed the bacterial pollution in the four parts, including air outlet, filter net, cooling fin and water sink, of ten household air-conditioners quantitatively and qualitatively from Chengdu, southwestern China. Results: The microbial cultivation results showed the large total bacterial counts of 5042.0, 9127.6, 6595.1, and 12296.2 CFU/cm2 in air outlet, filter net, cooling fin, and water sink. Furthermore, the sequencing data showed that these four parts displayed different bacterial characteristics. At the level of genus, Caproiciproducens and Acidipropionibacterium were predominant in air outlet. Bacillus, Acinetobacter, Paracoccus, and Corynebacterium were detected as the characteristic bacteria in filter net. For cooling fin, Rhodococcus, Achromobacter, and Nocardioides were the dominant bacteria. The genera of Methylobacterium-Methylorubrum, Brevibacterium, Stenotrophomonas, and Psychrobacter were identified as the bioindicators in water sink. The bioinformatic analysis on the sequencing data illustrated that the bacteria from air-conditioners were associated with metabolic disturbance. Discussion: This study reveals the distinct bacterial compositions in the different parts of air-conditioner, and provides new clues for the non-negligible bacterial pollution in this common appliance from Chinese households.

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This study explores the potential of synergistically reducing direct (refrigerant) and indirect (electricity) greenhouse gas (GHG) emissions in the global room air conditioning (RAC) sector, based on 80% of global RAC manufactured in China. Three scenarios are evaluated: Business-as-usual (BAU) based on maintaining refrigerant and energy efficiency levels from 2021 China RAC sales shares, Kigali Amendment compliant with 10% energy efficiency improvement by 2025 (KAE), and accelerated refrigerant transition and energy efficiency improvement (ATE). Each scenario considers the costs of refrigerant and efficiency measures for export market groups based on Kigali Amendment classifications. BAU predicts around 1 Gt CO2-eq average annual global RAC emissions (2022-2060). Cumulative emission reductions in China's RAC manufacturing under KAE and ATE are 12.2 and 17.2 Gt CO2-eq A5II and A5I (except China), presenting cost-effective abatement measures, with average costs of -$51.4 and -$68.8/t CO2-eq in KAE and ATE. Cumulative average abatement costs are around $18 and $4/t CO2-eq globally. KAE and ATE scenarios would avoid surface temperature rises of 0.023 (±0.002) °C and 0.027 (±0.003) °C, respectively, versus BAU. Collaboration between China and importing countries is urged to enhance energy efficiency in RACs traded, ensuring sustainable mitigation aligned with the Kigali Amendment.

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Individual heating systems, such as the air-source heat pump (ASHP) air-conditioner or floor heating (FH), are usually used by people living in the hot summer and cold winter (HSCW) zone of China to heat indoor climates in the winter. However, little research has been conducted in the HSCW zone on the thermal comfort difference between indoor climates heated by ASHP air-conditioners and those heated by floor heating, as well as how occupants adapt to different indoor climates. We conducted a comparative field experiment in ASHP-heated and FH-heated apartments in Nanjing to investigate how different types of heating systems influence the thermal sensation of occupants, and we conducted a comparative field experiment in ASHP-heated office buildings and naturally ventilated teaching buildings in Shanghai to investigate how occupants adapt to different indoor thermal environments. Indoor environmental parameters and body surface temperatures were measured using instruments, and occupants' thermal sensation, activity level, and clothing were evaluated using the questionnaire. The results show that floor heating improves thermal comfort by raising foot temperature compared to the ASHP air-conditioner, and that occupants become acclimatized to different indoor climates by adjusting neutral operative temperature. According to the findings, there is no need to overheat the indoor environment in the HSCW zone because occupants can adapt to their experienced thermal environment and it is critical to maintain warm foot temperature in the cool/cold indoor environment.

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The global "copper-poor and aluminum-rich" situation has made the possibility of "copper saving with aluminum" an important topic. This study established a framework for analyzing multiple substances' coupled flows at the product level based on material flow analysis (MFA), and took the household air conditioning system of the Chinese mainland in 2020 as an example to characterize the coupled flows of aluminum and copper. The results showed that the system consumed 0.69 million tons of aluminum and 2.10 million tons of copper, and discharged 0.17 million tons of aluminum and 0.43 million tons of copper to the environment cumulatively to achieve 13.2 million terajoules of final heat exchanged and serve 1.24 billion square meters during lifetime in mainland China alone, secondary aluminum and copper accounted for only 22.61% and 24.83% of the total consumption, and the in-use stocks increased by 0.19 million tons of aluminum and 0.70 million tons of copper. The external dependency of copper ore was 92.83%, which was significantly higher than the 44.29% of bauxite. The comprehensive utilization efficiency of copper reached 77.88%, which was slightly higher than the 70.80% of aluminum. The conclusion indicates that under the premise of meeting use requirements, promoting "replacing copper with aluminum" can improve the stability and safety of China's material supply chain, but there is a need to further boost the production efficiency of aluminum in primary production.

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Street view images are emerging as new street-level sources of urban environmental information. Accurate detection and quantification of urban air conditioners is crucial for evaluating the resilience of urban residential areas to heat wave disasters and formulating effective disaster prevention policies. Utilizing street view image data to predict the spatial coverage of urban air conditioners offers a simple and effective solution. However, detecting and accurately counting air conditioners in complex street-view environments remains challenging. This study introduced 3D parameter-free attention and coordinate attention modules into the target detection process to enhance the extraction of detailed features of air conditioner external units. It also integrated a small target detection layer to address the challenge of detecting small target objects that are easily missed. As a result, an improved algorithm named SC4-YOLOv7 was developed for detecting and recognizing air conditioner external units in street view images. To validate this new algorithm, we extracted air conditioner external units from street view images of residential buildings in Guilin City, Guangxi Zhuang Autonomous Region, China. The results of the study demonstrated that SC4-YOLOv7 significantly improved the average accuracy of recognizing air conditioner external units in street view images from 87.93% to 91.21% compared to the original YOLOv7 method while maintaining a high speed of image recognition detection. The algorithm has the potential to be extended to various applications requiring small target detection, enabling reliable detection and recognition in real street environments.

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The use of radiant panels in homes has increased recently because they do not cause a drafty feeling, unlike air conditioners. However, air conditioners are more power-efficient than radiant panels and have a higher coefficient of performance (COP). Therefore, combining radiant panels and air conditioning can provide an optimal solution for thermal control in residences. Energy simulation (ES) and computational fluid dynamics (CFD) can be used to simulate such environments. ES is suitable for non-steady state calculations, and combined with appropriate modeling, enables an accurate estimation of power consumption. Effective dehumidification becomes necessary, during summer as the relative humidity in a room increases. Both air conditioners and radiant panels can achieve this. This study developed a simulation tool that incorporates the effects of dehumidification. Based on a relative evaluation, a case was proposed where both energy efficiency and comfort were satisfied by jointly using air conditioners and radiant panels. The study found that a small number of panels could achieve the most balanced operation. The results of this study can serve as a reference for general housing, and the developed simulation tool can be applied to product development and building material design.

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A Gram-negative, rod-shaped and filamentous bacterium designated MD30BT was isolated from a biofilm hanging in water flowing from an air conditioner condensate drain line in Honolulu, Hawai'i. Based on 1517 nucleotides of the strain's 16S rRNA gene, its nearest neighbours are Chitinophaga rhizosphaerae T16R-86T (96.7 %), Chitinophaga caseinilytica S-52T (96.6 %), Chitinophaga lutea ZY74T (96.6 %), Chitinophaga niabensis JS13-10T (96.6 %) and Chitinophaga ginsengisoli Gsoil 052T (96.5 %). MD30BT cells are non-motile, strictly aerobic, and catalase and oxidase positive. Growth occurs between 10 and 45 °C. Major fatty acids in whole cells of MD30BT are 13-methyl tetradecanoic acid (34.1 %), cis-11-hexadecenoic acid (30.3 %), and 3-hydroxy, 15-methyl hexadecanoic acid (13.3 %). The quinone system contains predominantly menaquinone MK-7. The polar lipid profile contains the major lipids phosphatidylethanolamine, one unidentified lipid lacking a functional group, and two unidentified aminolipids. sym-Homospermidine is the major polyamine. The G+C content of the genome is 47.58 mol%. Based on phenotypic and genotypic differences between MD30BT and extant species in the Chitinophaga, we propose that MD30BT represents a new Chitinophaga species, for which the name Chitinophaga pendula sp. nov. is proposed to accommodate strain MD30BT as the type strain (DSM 112477T=NCTC 14606T).

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Due to energy constraints and people's increasing requirements for indoor thermal comfort, improving energy efficiency while ensuring thermal comfort has become the focus of research in the design and operation of HVAC systems. This study took office rooms with few people occupying them in Wuhan as the research object. The EnergyPlus-Fluent co-simulation method was used to study the impact of 12 forms of air distribution on the thermal environment and air-conditioner energy consumption. The results indicate that 3 m/s supply air velocity and 45° supply air angle are more suitable for the case model in this study. The EnergyPlus-Fluent co-simulation method used in this paper provides a reference for the study of indoor environments in offices with few people occupying them.

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Antibacterial nonwoven fabrics, incorporated with Ag, have been applied as masks and air conditioner filters to prevent the spread of disease from airborne respiratory pathogens. In this work, we present a comparison study of Ag ions: Ag and AgCu nanoparticles (NPs) coated onto nonwoven fabrics intended for use as air conditioner antibacterial filters. We illustrate their color changes and durability running in air conditioners using antibacterial activity testing and X-ray Photoelectron Spectroscopic (XPS) analysis. We found that AgCu NPs showed the best antibacterial efficacy and durability. XPS analysis indicated that the Ag concentration, on both the AgCu and Ag- NP-coated fibers, changed little. On the contrary, the Ag concentration on Ag ion-coated fibers decreased by ~30%, and the coated NPs aggregated over time. The color change in AgCu NP-coated fabric, from yellow to white, is caused by oxide shell formation over the NPs, with nearly 46% oxidized silver. Our results, both from antibacterial evaluation and wind blowing tests, indicate that AgCu NP-coated fibers have higher durability, while Ag ion-coated fibers have little durability in such applications. The enhanced durability of the AgCu NP-coated antibacterial fabrics can be attributed to stronger NP-fiber interactions and greater ion release.

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Introduction: Modernization has led to greater usage of Air Conditioners (ACs) in our daily lives. It is observed that the occupants of office buildings with ACs consistently report on average more symptoms than do occupants of office buildings with natural ventilation referred to as Sick Building Syndrome (SBS). The appearance of symptoms reduces work efficiency and increases absenteeism due to sickness (sickness absenteeism). Therefore, the present study was planned to evaluate the impact of usage of ACs on SBS and to find out the association of ACs with sickness absenteeism and lung function tests. Materials and Methods: This study was conducted on 200 healthy non-smoker adults in the age group of 18 to 45 years who were using ACs for at least 6 to 8 h/day for more than 2 years (group I). And 200 healthy adults, age and gender-matched, with the same work pattern, not using ACs at all served as controls (group II). The basic information on the usage of ACs and the prevalence of discomfort related to neural symptoms, respiratory symptoms, and skin and mucous membrane related to SBS was obtained through a questionnaire. Results: The building-related symptoms in group I males were more compared to group II males and significantly higher in group I males compared to females. We observed that the appearance of symptoms of SBS led to sickness absenteeism among group I participants. Lung function tests especially FVC, FEV1, PEFR, and MVV were significantly reduced among group I males and females compared to group II males and females. Conclusion: ACs have a profound effect on the quality of the air we breathe and on human health than just lowering the temperature. There is a higher prevalence of SBS-Respiratory and allergic symptoms in AC users.

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This research paper presents an analysis of the propagation of the SARS-CoV-2, or other similar pathogens, in a hospital isolation room using computational fluid dynamics (CFD) and Lagrangian Coherent Structures (LCS). The study investigates the airflow dispersion and droplets in the room under air conditioning vent and sanitizer conditions. The CFD simulation results show that both the air conditioner and sanitizer systems significantly influence the dispersion of the virus in the room. The use of LCS enables acquiring a deep understanding of the dispersion of suspended particles, providing insights into the mechanisms of virus transmission. The findings of this study could help in developing strategies for improving the design and operation of isolation rooms to minimize the likelihood of virus dissemination within hospitals.

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ANALYSIS: of air conditioner (AC) filter dust can reveal the level of organophosphate ester (OPE) pollution in indoor environments, but comprehensive research on this topic remains lacking. This study combined non-targeted and targeted analysis to screen and analyze 101 samples of AC filter dust, settled dust, and air obtained in 6 indoor environments. Phosphorus-containing organic compounds account for a large proportion of the organic compounds found in indoor environments, and OPEs might be the main pollutants. Using toxicity data and traditional priority polycyclic aromatic hydrocarbons for toxicity prediction of OPEs, 11 OPEs were prioritized for further quantitative analysis. The concentration of OPEs in AC filter dust was highest, followed in descending order by that in settled dust and that in air. The concentration of OPEs in AC filter dust in the residence was two to seven times greater than that in the other indoor environments. More than 56% of the OPEs in AC filter dust showed significant correlation, while those in settled dust and air were weakly correlated, suggesting that large amounts of OPEs collected over long periods could have a common source. Fugacity results showed that OPEs were transferred easily from dust to air, and that dust was the main source of OPEs. The values of both the carcinogenic risk and the hazard index were lower than the corresponding theoretical risk thresholds, indicating low risk to residents through exposure to OPEs in indoor environments. However, it is necessary to remove AC filter dust in a timely manner to prevent it becoming a pollution sink of OPEs that could be rereleased and endanger human health. This study has important implications for comprehensive understanding of the distribution, toxicity, sources, and risks of OPEs in indoor environments.

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The aim of this study was to find the source of Acinetobacter baumannii in the intensive care unit (ICU) after an outbreak during the coronavirus disease 2019 (COVID-19) pandemic, as there was no A. baumannii detected on usually screened susceptible surfaces. The screening of the ICU environment was done in April 2021 when eleven different samples were taken. One A. baumannii isolate was recovered from the air conditioner and was compared with four clinical A. baumannii isolates obtained from patients hospitalized in January 2021. Isolates were confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), minimum inhibitory concentrations (MICs) were determined, and the multilocus sequence typing (MLST) was performed. The molecular identification of A. baumannii isolates as ST208, the presence of the same blaOXA-23 carbapenemase gene, and the same antibiotic susceptibility profile suggest that the isolate recovered from the air conditioner is the same as the isolates recovered from hospitalized patients. The environmental isolate was recovered three months later than the clinical isolates, emphasizing the ability of A. baumannii to survive on dry abiotic surfaces. The air conditioner in the clinical environment is an important but undoubtedly neglected source of A. baumannii outbreaks, hence, frequent disinfection of hospital air conditioners with appropriate disinfectants is mandatory to mitigate the circulation of A. baumannii between patients and the hospital environment.

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Air conditioners are typically installed in buildings and vehicles to control thermal conditions for long periods of time. Air conditioners generate certain types of sounds while functioning, which are among the main noise sources in buildings and vehicles. Most sounds produced by the air conditioner do not change with time, and the sound quality of steady sounds has been investigated. However, air conditioners can generate low-level impulsive sounds. Customers complain of the discomfort caused when these sounds disturb the silence in their living rooms and bedrooms. This study aimed to determine the physical factors that have a significant effect on physiological responses to low-level impulsive sounds produced by air conditioners. We used physiological responses because it is difficult for people to evaluate sounds psychologically when they are sleeping or are not focused on the sounds. The A-weighted equivalent continuous sound pressure level (LAeq) and the factors extracted from the autocorrelation function (ACF) were evaluated as physical factors. Participant responses on electroencephalography (EEG) were evaluated. The correlation between the EEG responses and ACF factors was determined. The LAeq, peak, and delay time to the first maximum peak of the ACF were identified as significant factors for physiological responses to low-level impulsive sounds.

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Coronavirus disease (COVID-19), which emerged in 2019, has induced worldwide chaos. The main cause of COVID-19 mass infection indoors is the spread of virus-containing droplets via indoor airflow, which is affected by air conditioners and purifiers. Here, ten experimental cases were established to analyze how use of air purifiers affects the spread of virus-containing droplets. The experiments were conducted in a school classroom with an air conditioner in summer. In the droplet dispersion experiment, paraffin oil was used as the droplet substance. Two main scenarios were simulated: (1) an infected student was seated in the back of the classroom; and (2) the teacher, standing in the front of the classroom, was infected. The results were expressed using two parameters: peak concentration and loss rate, which reflect the degree of direct and indirect infection (airborne infection), respectively. The air purifier induced a peak concentration decrease of 42% or an increase of 278%, depending on its location in the classroom. Conversely, when the air purifier was operated in the high mode (flow rate = 500 CMH; cubic meters per hour), the loss rate showed that the amount of droplet nuclei only decreased by 39% and the droplet amount decreased by 22%. Thus, the airborne infection degree can be significantly reduced. Finally, the use of air purifiers in the summer may be helpful in preventing group infections by reducing the loss rate and peak concentration if the air purifier is placed in a strategic location, according to the airflow of the corresponding room.

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Dust in the home environment is thought to be a potential trigger for increasing allergic diseases, such as allergic rash, rhinitis, asthma, and other conditions, associated with dust mites. To verify the status of dust mite prevalence in indoor surroundings, we collected 189 dust samples from the air conditioner filters (n = 75) and floors (n = 114) of households, schools, and hotels in the Anhui area, China. All samples were measured for dust mite breeding rate and breeding density under light microscopy and analyzed for dust mite species Dermatophagoides farinae 1 (Der f 1) and Dermatophagoides pteronyssinus 1 (Der p 1) allergen using enzyme-linked immunosorbent assay (ELISA). The dust mite breeding rates were 34.67% (26/75) and 20.18% (23/114), respectively, in the dust samples from the floor and air conditioning filters. The breeding density was the highest in households (10/g), followed by schools (9/g) and hotels (4/g). ELISA indicated that the allergen threshold (2.0 µg/g dust) of Der f 1 was exceeded in only two samples and Der p 1 in one sample. Additionally, a questionnaire was used to investigate the health knowledge on allergic diseases involved in indoor facilities, finding that most allergy sufferers were aware that indoor dust might be responsible for their conditions. The findings suggest that regular maintenance of indoor hygiene and cleaning of air-conditioning filters should reduce the risks of exposure to indoor allergens.

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Background: Humidifier lung (HL) is a hypersensitivity pneumonitis resulting from exposure to humidifiers, with fungi from the humidifier as one of the etiologic agents. However, identification of the fungal species responsible for each case can be challenging because of difficulties in culturing fungi, their accurate identification, and interpreting the results of specific serum IgG testing. Objective: To clarify the best way to determine the causative fungal species of each HL case. Methods: We report 2 cases with HL in which rare fungi were identified as causative agents. In addition, we searched MEDLINE for previous publications on HL caused by fungi and performed a literature review focusing on clinical testing for the determination of causal fungal species. Results: In our 2 cases, we identified Fusarium oxysporum species complex, Purpureocillium lilacinum, Acremonium sclerotigenum/egyptiacum as the causative fungal species, based on findings that these could be cultured from humidifier water (HW) and precipitins against these fungi were also positive. The literature review identified 31 HL cases in which the causative fungal species had been documented. In more than half of the cases (17 of 31) there was a concordance between the fungal species cultured from HW and the presence of specific IgG in the blood. Conclusion: We recommend performing culture of fungi from HW and specific serum IgG testing for the accurate determination of the causative fungal species in HL, and concordance between them serves as a rationale for the determination of causative fungal species.

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HVAC systems have a significant impact on the indoor environment, and microbial contamination in HVAC systems has a significant effect on the indoor air quality. In this study, to gain a better understanding of the microbial contamination inside ACs, we used NGS to analyze the 16S rRNA gene of bacteria adhering to AC filters, cooling coils, fans, and air outlet surfaces. The five phyla in terms of the highest relative abundance were Proteobacteria, Firmicutes, Actinobacteria, Cyanobacteria, and Bacteroidetes. The surface of an AC filter provides a history of indoor airborne bacterial contamination, and of the 10 bacterial genera we detected with the highest abundance (in the following order: Pseudomonas > Staphylococcus > Paracoccus > Corynebacterium > Acinetobacter > Streptococcus > Methylobacterium > Enhydrobacter > Sphingomonas > Actinotignum) on the filter surface, the top 6 genera were Gram-negative bacteria. Furthermore, the seventh-most abundant genus adhering to the filter surface (Methylobacterium) was the second-most abundant genus on the cooling coil and fan, and the ninth-most abundant genus on the air filter (Sphingomonas) was the third-most abundant genus on the cooling coil. Various factors impact the bacterial flora inside AC units, including the location of the house, AC unit usage, and occupant activity.

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Fungi, a major allergen associated with asthma onset and severity, can contaminate air conditioners if not properly maintained. We surveyed the prevalence and risk factors associated with fungal contamination of air conditioners and patient behavior to reduce this contamination. Japanese adults aged ≥30 years registered in the database of an Internet research company were asked to participate in an online survey. A moldy odor from the air conditioners in their residences was used as an indicator of fungal contamination. Among a total of 1006 adults, including 631 patients with asthma, 37.1% reported a moldy odor from air conditioners. The prevalence was higher in residences with indoor condensation and in air conditioners used for ≥6 years or frequently during the summer, but was lower in air conditioners with an auto-cleaning function. The risk of indoor condensation was higher in apartments, in the presence of an aquarium, and in the absence of a 24-h ventilation system. These risk factors did not differ between the residences or air conditioners of participants with and without asthma. Asthmatic patients were conscious of indoor air quality; however, do not necessarily take appropriate measures to reduce indoor mold contamination, possibly due to a lack of knowledge. In conclusion, appropriate patient education is required to reduce environmental fungal contamination and improve asthma control.

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Regulation of indoor temperature based on neurophysiological and psychological signals is one of the most promising technologies for intelligent buildings. In this study, we developed a system for closed-loop control of indoor temperature based on brain-computer interface (BCI) technology for the first time. Electroencephalogram (EEG) signals were collected from subjects for two room temperature categories (cool comfortable and hot uncomfortable) and used to build a thermal-sensation discrimination model (TSDM) with an ensemble learning method. Then, an online BCI system was developed based on the TSDM. In the online room temperature control experiment, when the TSDM detected that the subjects felt hot and uncomfortable, BCI would automatically turn on the air conditioner, and when the TSDM detected that the subjects felt cool and comfortable, BCI would automatically turn off the air conditioner. The results of online experiments in a hot environment showed that a BCI could significantly improve the thermal comfort of subjects (the subjective thermal comfort score decreased from 2.45 (hot uncomfortable) to 0.55 (cool comfortable), p < 0.001). A parallel experiment further showed that if the subjects wore thicker clothes during the experiment, the BCI would turn on the air conditioner for a longer time to ensure the thermal comfort of the subjects. This has further confirmed the effectiveness of TSDM model in evaluating thermal sensation under the dynamic change of room temperature and showed the model's good robustness. This study proposed a new paradigm of human-building interaction, which is expected to play a promising role in the development of human-centered intelligent buildings.

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