1
|
Wang MH, Wu XM, Lai ACK. Experimental study on the effect of light source arrangements on the disinfection performance of upper-room 222 nm Far-UVC. JOURNAL OF HAZARDOUS MATERIALS 2024; 479:135571. [PMID: 39197280 DOI: 10.1016/j.jhazmat.2024.135571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2024] [Revised: 08/15/2024] [Accepted: 08/16/2024] [Indexed: 09/01/2024]
Abstract
The air disinfection efficacy of upper-room 222 nm Far-UVC was experimentally investigated in a real-size chamber under well-mixed air conditions. Two bacteria (Escherichia coli, Staphylococcus epidermidis) and two bacteriophages (MS2, and P22) were selected for the test. The study considered different lamp source arrangements, including single and double sources, stationary and rotating operating modes, and an overlapping mode with a 45° irradiation angle. A numerical view-factor model was developed to analyze the irradiance distributions. Four irradiation angles, 30°, 45°, 60°, and 90°, were chosen. The results show that the lamps operating with an irradiation angle of 45° provide the highest chamber-averaged irradiance. This suggests an optimal irradiance level for a given room dimension, as inferred from the view factor model. Experimental results indicated that the overlapping mode with a 45° irradiation angle consistently outperformed both the stationary mode and rotating mode in disinfection. This can be attributed to the higher chamber-averaged irradiance, which is also supported by the numerical model predictions. The increment ratios ranged from 14.9 % to 42.9 % compared to the stationary mode. The susceptibility constants of Escherichia coli, Staphylococcus epidermidis, MS2, and P22 were measured as 0.572 m2/J, 0.099 m2/J, 0.060 m2/J, and 0.081 m2/J respectively.
Collapse
Affiliation(s)
- M H Wang
- Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Hong Kong
| | - X M Wu
- School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Hong Kong
| | - A C K Lai
- School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Hong Kong.
| |
Collapse
|
2
|
Guo K, Wan Z, Jiang Y, Ho KF, Chen C. A liquid culture method assisted by ATP analysis for accelerating laboratory experiments on ultraviolet disinfection of airborne bacteria. JOURNAL OF HAZARDOUS MATERIALS 2024; 478:135518. [PMID: 39154474 DOI: 10.1016/j.jhazmat.2024.135518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 08/08/2024] [Accepted: 08/12/2024] [Indexed: 08/20/2024]
Abstract
The solid culture method for measuring the efficiency of ultraviolet (UV) disinfection of airborne bacteria is time-consuming, typically taking 12-48 h. To expedite such experiments, this study proposed a liquid culture method assisted by adenosine triphosphate (ATP) analysis, as a liquid culture is faster than a solid culture, and measurement of ATP does not require waiting for visible colonies to form. Escherichia coli (E. coli) was used as the experimental bacterium. This study first compared the log reduction of bacteria in liquid as measured by the proposed method and by the traditional solid culture method. The minimum liquid culture time was determined for different bacterial concentration ranges. Finally, the feasibility of the proposed method was validated by UV disinfection experiments on airborne bacteria. The results indicated that the proposed method measured a similar log reduction to that of the solid culture method in liquid experiments. The minimum liquid culture time for E. coli in 105-106 colony forming units (CFU)/mL was 2 h. The validation experiments demonstrated that the proposed method is capable of measuring the UV disinfection efficiency of airborne bacteria. The proposed method can accelerate laboratory experiments on UV disinfection of airborne bacteria, which in turn can support the effective design and utilization of UV disinfection in real life.
Collapse
Affiliation(s)
- Kangqi Guo
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, N.T. 999077, Hong Kong SAR, China
| | - Zhishang Wan
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Kowloon 999077, Hong Kong SAR, China
| | - Yi Jiang
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Kowloon 999077, Hong Kong SAR, China
| | - Kin-Fai Ho
- The Jockey Club School of Public Health and Primary Care, The Chinese University of Hong Kong, Shatin, N.T. 999077, Hong Kong SAR, China.
| | - Chun Chen
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, N.T. 999077, Hong Kong SAR, China; Institute of Environment, Energy and Sustainability, The Chinese University of Hong Kong, Shatin, N.T. 999077, Hong Kong SAR, China.
| |
Collapse
|
3
|
Yao G, Liu Z, Liu H, Jiang C, Li Y, Liu J, He J. Air disinfection performance of upper-room ultraviolet germicidal irradiation (UR-UVGI) system in a multi-compartment dental clinic. JOURNAL OF HAZARDOUS MATERIALS 2024; 477:135383. [PMID: 39094316 DOI: 10.1016/j.jhazmat.2024.135383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2024] [Revised: 07/27/2024] [Accepted: 07/29/2024] [Indexed: 08/04/2024]
Abstract
Multi-compartment dental clinics present significant airborne cross-infection risks. Upper-room ultraviolet germicidal irradiation (UR-UVGI) system have shown promise in preventing airborne pathogens, but its available application data are insufficient in multi-compartment dental clinics. Therefore, the UR-UVGI system's performance in a multi-compartment dental clinic was comprehensively evaluated in this study. The accuracy of the turbulence and drift flux models was verified by experimental data from ultrasonic scaling. The effects of the ventilation rate, irradiation zone volume, and irradiation flux on UR-UVGI performance were analyzed using computational fluid dynamics coupled with a UV inactivation model. Different patient numbers were considered. The results showed that UR-UVGI significantly reduced virus concentrations and outperformed increased ventilation rates alone. At a ventilation rate of six air changes per hour (ACH), UR-UVGI with an irradiation zone volume of 20% and irradiation flux of 5 μW/cm2 achieved a 70.44% average virus reduction in the whole room (WR), outperforming the impact of doubling the ventilation rate from 6 to 12 ACH without UR-UVGI. The highest disinfection efficiency of UR-UVGI decreased for WRs with more patients. The compartment treating patients exhibited significantly lower disinfection efficiency than others. Moreover, optimal UR-UVGI performance occurs at lower ventilation rates, achieving over 80% virus disinfection in WR. Additionally, exceeding an irradiation zone volume of 20% or an irradiation flux of 5 μW/cm2 notably reduces the improvement rates of UR-UVGI performance. These findings provide a scientific reference for strategically applying UR-UVGI in multi-compartment dental clinics.
Collapse
Affiliation(s)
- Guangpeng Yao
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei 071003, PR China
| | - Zhijian Liu
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei 071003, PR China.
| | - Haiyang Liu
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei 071003, PR China
| | - Chuan Jiang
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei 071003, PR China
| | - Yabin Li
- The Fifth Medical Center of PLA General Hospital, Beijing 100039, PR China
| | - Jia Liu
- The Fifth Medical Center of PLA General Hospital, Beijing 100039, PR China
| | - Junzhou He
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei 071003, PR China.
| |
Collapse
|
4
|
Alhussain H, Ghani S, Eltai NO. Breathing Clean Air: Navigating Indoor Air Purification Techniques and Finding the Ideal Solution. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2024; 21:1107. [PMID: 39200716 PMCID: PMC11354768 DOI: 10.3390/ijerph21081107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2024] [Revised: 08/05/2024] [Accepted: 08/07/2024] [Indexed: 09/02/2024]
Abstract
The prevalence of airborne pathogens in indoor environments presents significant health risks due to prolonged human occupancy. This review addresses diverse air purification systems to combat airborne pathogens and the factors influencing their efficacy. Indoor aerosols, including bioaerosols, harbor biological contaminants from respiratory emissions, highlighting the need for efficient air disinfection strategies. The COVID-19 pandemic has emphasized the dangers of airborne transmission, highlighting the importance of comprehending how pathogens spread indoors. Various pathogens, from viruses like SARS-CoV-2 to bacteria like Mycobacterium (My) tuberculosis, exploit unique respiratory microenvironments for transmission, necessitating targeted air purification solutions. Air disinfection methods encompass strategies to reduce aerosol concentration and inactivate viable bioaerosols. Techniques like ultraviolet germicidal irradiation (UVGI), photocatalytic oxidation (PCO), filters, and unipolar ion emission are explored for their specific roles in mitigating airborne pathogens. This review examines air purification systems, detailing their operational principles, advantages, and limitations. Moreover, it elucidates key factors influencing system performance. In conclusion, this review aims to provide practical knowledge to professionals involved in indoor air quality management, enabling informed decisions for deploying efficient air purification strategies to safeguard public health in indoor environments.
Collapse
Affiliation(s)
- Hashim Alhussain
- Biomedical Research Center, Qatar University, Doha P.O. Box 2713, Qatar;
| | - Saud Ghani
- Department of Industrial and Mechanical Engineering, Qatar University, Doha P.O. Box 2713, Qatar;
| | - Nahla O. Eltai
- Biomedical Research Center, Qatar University, Doha P.O. Box 2713, Qatar;
| |
Collapse
|
5
|
Liu H, Liu Z, He J, Hu C, Rong R, Han H, Wang L, Wang D. Reducing airborne transmission of SARS-CoV-2 by an upper-room ultraviolet germicidal irradiation system in a hospital isolation environment. ENVIRONMENTAL RESEARCH 2023; 237:116952. [PMID: 37619635 DOI: 10.1016/j.envres.2023.116952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 08/08/2023] [Accepted: 08/21/2023] [Indexed: 08/26/2023]
Abstract
Upper-room ultraviolet germicidal irradiation (UVGI) technology can potentially inhibit the transmission of airborne disease pathogens. There is a lack of quantitative evaluation of the performance of the upper-room UVGI for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) airborne transmission under the combined effects of ventilation and UV irradiation. Therefore, this study aimed to explore the performance of the upper-room UVGI system for reducing SARS-CoV-2 virus transmission in a hospital isolation environment. Computational fluid dynamics and virological data on SARS-CoV-2 were integrated to obtain virus aerosol exposure in the hospital isolation environment containing buffer rooms, wards and bathrooms. The UV inactivation model was applied to investigate the effects of ventilation rate, irradiation flux and irradiation height on the upper-room UVGI performance. The results showed that increasing ventilation rate from 8 to 16 air changes per hour (ACH) without UVGI obtained 54.32% and 45.63% virus reduction in the wards and bathrooms, respectively. However, the upper-room UVGI could achieve 90.43% and 99.09% virus disinfection, respectively, with the ventilation rate of 8 ACH and the irradiation flux of 10 μW cm-2. Higher percentage of virus could be inactivated by the upper-room UVGI at a lower ventilation rate; the rate of improvement of UVGI elimination effect slowed down with the increase of irradiation flux. Increase irradiation height at lower ventilation rate was more effective in improving the UVGI performance than the increase in irradiation flux at smaller irradiation height. These results could provide theoretical support for the practical application of UVGI in hospital isolation environments.
Collapse
Affiliation(s)
- Haiyang Liu
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Zhijian Liu
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China.
| | - Junzhou He
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Chenxing Hu
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Rui Rong
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Hao Han
- State Key Laboratory of NBC Protection for Civilian, Beijing, 100191, China.
| | - Lingyun Wang
- State Key Laboratory of NBC Protection for Civilian, Beijing, 100191, China
| | - Desheng Wang
- State Key Laboratory of NBC Protection for Civilian, Beijing, 100191, China
| |
Collapse
|
6
|
Lu YH, Wu H, Zhang HH, Li WS, Lai ACK. Synergistic disinfection of aerosolized bacteria and bacteriophage by far-UVC (222-nm) and negative air ions. JOURNAL OF HAZARDOUS MATERIALS 2023; 441:129876. [PMID: 36087531 DOI: 10.1016/j.jhazmat.2022.129876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 08/22/2022] [Accepted: 08/28/2022] [Indexed: 06/15/2023]
Abstract
Air ionizers and 222-nm krypton-chlorine (KrCl) excilamp have proven to be effective disinfection apparatus for bacteria and viruses with limited health risks. We determined inactivation efficiencies by operating them individually and in combined modules. Gram-positive and gram-negative bacteria, non-enveloped dsDNA virus, and enveloped dsRNA virus were examined in a designed air disinfection system. Our results showed that the bioaerosols were inactivated efficiently by negative ionizers and far-UVC (222-nm), either used individually or in combination. Among which the combined modules of negative ionizers and KrCl excilamp had the best disinfection performance for the bacteria. The aerosolized virus P22 and Phi 6 were more susceptible to 222-nm emitted by KrCl excilamp than negative air ions. Significant greater inactivation of bacterial bioaerosols were identified after treated by combined treatment of negative air ion and far-UVC for 2 minutes (Escherichia coli, 6.25 natural log (ln) reduction; Staphylococcus epidermidis, 3.66 ln reduction), as compared to the mean sum value of inactivation results by respective individual treatment of negative ionizers and KrCl excilamp (Escherichia coli, 4.34 ln; Staphylococcus epidermidis, 1.75 ln), indicating a synergistic inactivation effect. The findings provide important baseline data to support the design and development of safe and high-efficient disinfection systems.
Collapse
Affiliation(s)
- Y H Lu
- Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong China
| | - H Wu
- Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong China; Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong China
| | - H H Zhang
- Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong China
| | - W S Li
- School of Public Health, The University of Hong Kong, Pokfulam, Hong Kong China
| | - A C K Lai
- Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong China.
| |
Collapse
|
7
|
Nunayon SS, Wang M, Zhang HH, Lai ACK. Evaluating the efficacy of a rotating upper-room UVC-LED irradiation device in inactivating aerosolized Escherichia coli under different disinfection ranges, air mixing, and irradiation conditions. JOURNAL OF HAZARDOUS MATERIALS 2022; 440:129791. [PMID: 36027747 DOI: 10.1016/j.jhazmat.2022.129791] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 08/09/2022] [Accepted: 08/15/2022] [Indexed: 06/15/2023]
Abstract
Cost-effective and safe air disinfection methods are urgently needed in various environmental public settings. A novel UVC-based disinfection system was designed and tested to provide a promising solution because of its effective inactivation of indoor bioaerosols at a low cost. UVC light-emitting diodes (UVC-LEDs) were utilized as the irradiation source. This system has the unique feature of rotating the UVC-LEDs to generate a "scanning irradiation" zone. Escherichia coli was aerosolized into an experimental chamber, exposed to UVC-LEDs, and sampled using an impactor. Effects of air mixing (well-mixed vs. poorly-mixed), transmission range (short vs. long), and irradiation mode (stationary vs. rotating) were evaluated. The system performs significantly well under the poorly-mixed condition. The results obtained from the short disinfection range indicate that the rotating UVC was approximately 70.5 % more effective than the stationary UVC for the poorly-mixed case. Further, we evaluated the performance of the long disinfection range under a poorly-mixed situation, and the disinfection efficacy was 84.6 % higher for the rotating irradiation than that of the stationary. About 0.59-1.34 J/m2 UV dose can be used to obtain one-log inactivation of E. coli. In conclusion, the novel rotating upper-room UVC-LED system is effective in reducing indoor pathogen transmission, and our findings are highly significant to a growing field where LEDs are applied for disinfection.
Collapse
Affiliation(s)
- Sunday S Nunayon
- Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China; Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Minghao Wang
- Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
| | - Hui H Zhang
- Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
| | - Alvin C K Lai
- Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
| |
Collapse
|
8
|
Xia T, Guo K, Pan Y, An Y, Chen C. Temporal and spatial far-ultraviolet disinfection of exhaled bioaerosols in a mechanically ventilated space. JOURNAL OF HAZARDOUS MATERIALS 2022; 436:129241. [PMID: 35739760 DOI: 10.1016/j.jhazmat.2022.129241] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 05/18/2022] [Accepted: 05/24/2022] [Indexed: 06/15/2023]
Abstract
Far-UVC with a peak wavelength of 222 nm can potentially be used to inactivate exhaled bioaerosols in an efficient and safe manner. Therefore, this study aimed to experimentally explore the effectiveness of a 222 nm far-UVC light for inactivating bioaerosols, represented by E. coli, exhaled from a manikin in a chamber with mechanical ventilation. The spatial irradiance distribution from the far-UVC light was measured. The susceptibility constant (z-value) for E. coli under the far-UVC light was experimentally obtained. The temporal and spatial concentrations of the bioaerosols exhaled from the manikin were measured under three typical ventilation rates (4, 10, and 36 ACH). According to the results, when the far-UVC light was turned on, the bioaerosol concentrations were lower than those without the far-UVC light under all three ventilation rates, suggesting that far-UVC light can effectively disinfect E. coli under mechanical ventilation. However, the disinfection efficiency of the far-UVC light decreased as the ventilation rate increased, which indicated that the far-UVC light played a more important role in bioaerosol removal under a lower ventilation rate. In general, the results supported the feasibility of using 222 nm far-UVC light for disinfection of exhaled bioaerosols in mechanically ventilated spaces to reduce infection risks.
Collapse
Affiliation(s)
- Tongling Xia
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin N.T. 999077, Hong Kong SAR, China; Breakthrough Technology Center, Midea Building Technologies, Foshan 528000, China
| | - Kangqi Guo
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin N.T. 999077, Hong Kong SAR, China
| | - Yue Pan
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin N.T. 999077, Hong Kong SAR, China
| | - Yuting An
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin N.T. 999077, Hong Kong SAR, China
| | - Chun Chen
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin N.T. 999077, Hong Kong SAR, China; Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China.
| |
Collapse
|
9
|
Nicolau T, Gomes Filho N, Padrão J, Zille A. A Comprehensive Analysis of the UVC LEDs' Applications and Decontamination Capability. MATERIALS (BASEL, SWITZERLAND) 2022; 15:2854. [PMID: 35454546 PMCID: PMC9028096 DOI: 10.3390/ma15082854] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 04/08/2022] [Accepted: 04/11/2022] [Indexed: 01/27/2023]
Abstract
The application of light-emitting diodes (LEDs) has been gaining popularity over the last decades. LEDs have advantages compared to traditional light sources in terms of lifecycle, robustness, compactness, flexibility, and the absence of non-hazardous material. Combining these advantages with the possibility of emitting Ultraviolet C (UVC) makes LEDs serious candidates for light sources in decontamination systems. Nevertheless, it is unclear if they present better decontamination effectiveness than traditional mercury vapor lamps. Hence, this research uses a systematic literature review (SLR) to enlighten three aspects: (1) UVC LEDs' application according to the field, (2) UVC LEDs' application in terms of different biological indicators, and (3) the decontamination effectiveness of UVC LEDs in comparison to conventional lamps. UVC LEDs have spread across multiple areas, ranging from health applications to wastewater or food decontamination. The UVC LEDs' decontamination effectiveness is as good as mercury vapor lamps. In some cases, LEDs even provide better results than conventional mercury vapor lamps. However, the increase in the targets' complexity (e.g., multilayers or thicker individual layers) may reduce the UVC decontamination efficacy. Therefore, UVC LEDs still require considerable optimization. These findings are stimulating for developing industrial or final users' applications.
Collapse
Affiliation(s)
- Talita Nicolau
- 2C2T-Centre for Textile Science and Technology, University of Minho, 4800-058 Guimaraes, Portugal
| | - Núbio Gomes Filho
- School of Economics and Management, University of Minho, 4710-057 Braga, Portugal
| | - Jorge Padrão
- 2C2T-Centre for Textile Science and Technology, University of Minho, 4800-058 Guimaraes, Portugal
| | - Andrea Zille
- 2C2T-Centre for Textile Science and Technology, University of Minho, 4800-058 Guimaraes, Portugal
| |
Collapse
|
10
|
Shamim JA, Hsu WL, Daiguji H. Review of component designs for post-COVID-19 HVAC systems: Possibilities and challenges. Heliyon 2022; 8:e09001. [PMID: 35224237 PMCID: PMC8863315 DOI: 10.1016/j.heliyon.2022.e09001] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 09/16/2021] [Accepted: 02/18/2022] [Indexed: 11/01/2022] Open
Abstract
The globally occurring recurrent waves of the COVID-19 pandemic, primarily caused by the transmission of aerosolized droplets from an infected person to a healthy person in the indoor environment, has led to the urgency of designing new modes of indoor ventilation. To prevent cross-contaminations due to airborne viruses, bacteria, and other pollutants in indoor environments, heating ventilation and air-conditioning (HVAC) systems need to be redesigned with anti-pandemic components. The three vital anti-pandemic components for the post-COVID-19 HVAC systems, as identified by the authors, are: a biological contaminant inactivation unit, a volatile organic compound decomposition unit, and an advanced air filtration unit. The purpose of the current article is to provide an overview of the latest research outcomes toward designing these anti-pandemic components and pointing out the future promises and challenges. In addition, the role of personalized ventilation in minimizing the risk of indoor cross-contamination by employing various air terminal devices is discussed. The authors believe that this article will encourage HVAC designers to develop effective anti-pandemic components to minimize the indoor airborne transmission.
Collapse
Affiliation(s)
- Jubair A Shamim
- Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Wei-Lun Hsu
- Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Hirofumi Daiguji
- Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| |
Collapse
|
11
|
Nunayon SS, Zhang HH, Chan V, Kong RYC, Lai ACK. Study of synergistic disinfection by UVC and positive/negative air ions for aerosolized Escherichia coli, Salmonella typhimurium, and Staphylococcus epidermidis in ventilation duct flow. INDOOR AIR 2022; 32:e12957. [PMID: 34796996 DOI: 10.1111/ina.12957] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Revised: 10/29/2021] [Accepted: 10/30/2021] [Indexed: 06/13/2023]
Abstract
The efficacy of the in-duct application of ultraviolet waveband C (UVC) emitting at 254 nm wavelength and air ions against aerosolized bacteria was studied in a full-scale 9-m long ventilation duct. Combined positive and negative ion polarities (bipolar ions) and combined UVC and ions were tested. The UVC was generated by a mercury-type UVC lamp and air ions were generated by positive and negative polarity ionizers. Escherichia coli (E. coli), Salmonella typhimurium (S. typhimurium), and Staphylococcus epidermidis (S. epidermidis)were tested at a concentration of 108 to 109 cells in 50 ml of sterilized distilled water. The case in which the positive ionizer was placed first, followed by the negative ionizer, demonstrated significantly higher disinfection efficiencies for E. coli (p = 0.007) and S. typhimurium (p < 0.001), but lower efficiency for S. epidermidis (p = 0.01) than the reversed sequence. The combination of UVC (3.71 J/m2 ) and air ions (1.13 × 1012 ions/m3 for positive ions and 8.00 × 1011 ions/m3 for negative ions) led to higher inactivation than individual disinfection agents operating under the same dose. A synergetic inactivation effect was observed for S. epidermidis under the combined UVC and positive ion case, while the combined UVC and negative ion case showed significant synergy effects for E. coli and S. typhimurium.
Collapse
Affiliation(s)
- Sunday S Nunayon
- Department of Architecture and Civil Engineering, City University of Hong Kong, Hong Kong, China
| | - Hui H Zhang
- Department of Architecture and Civil Engineering, City University of Hong Kong, Hong Kong, China
| | - Vincent Chan
- Department of Biomedical Engineering, Khalifa University of Science and Technology, Abu Dhabi, UAE
| | - Richard Y C Kong
- Department of Chemistry, City University of Hong Kong, Hong Kong, China
| | - Alvin C K Lai
- Department of Architecture and Civil Engineering, City University of Hong Kong, Hong Kong, China
| |
Collapse
|
12
|
Mishra D, Yadav R, Pratap Singh R, Taneja A, Tiwari R, Khare P. The incorporation of lemongrass oil into chitosan-nanocellulose composite for bioaerosol reduction in indoor air. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 285:117407. [PMID: 34049138 DOI: 10.1016/j.envpol.2021.117407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 04/30/2021] [Accepted: 05/16/2021] [Indexed: 06/12/2023]
Abstract
The bioaerosols present in indoor air play a major role in the transmission of infectious diseases to humans, therefore concern about their exposure is increased recently. In this regard, the present investigation described the preparation of lemongrass essential oil (LGEO) loaded chitosan and cellulose nanofibers composites (CH/CNF) for controlling the indoor air bioaerosol. The evaluation of the inhibitory effect of the composite system on culturable bacteria of the indoor air was done at different sites (air volume from 30 m3 to 80 m3) and in different size fractions of aerosol (<0.25 μm-2.5 μm). The composite system had high encapsulation efficiency (88-91%) and citrals content. A significant reduction in culturable bacteria of aerosol (from 6.23 log CFUm-3 to 2.33 log CFUm-3) was observed in presence of cellulose nanofibers and chitosan composites. The bacterial strains such as Staphylococcus sp., Bacillus cereus, Bacillus pseudomycoides sp., Pseudomonas otitidis, and Pseudomonas sp. Cf0-3 in bioaerosols were inhibited dominantly due to the diffusion of aroma molecules in indoor air. The results indicate that the interaction of diffused aroma molecule from the composite system with bacterial strains enhanced the production of ROS, resulting in loss of membrane integrity of bacterial cells. Among different size fractions of aerosol, the composite system was more effective in finer size fractions (<0.25 μm) of aerosol due to the interaction of smaller aroma compounds with bacterial cells. The study revealed that LGEO loaded chitosan and cellulose nanofibers composites could be a good option for controlling the culturable bacteria even in small-sized respirable bioaerosol.
Collapse
Affiliation(s)
- Disha Mishra
- Division of Crop Production and Protection, CSIR-Central Institute of Medicinal and Aromatic Plants, Lucknow, 226 015, India
| | - Ranu Yadav
- Division of Crop Production and Protection, CSIR-Central Institute of Medicinal and Aromatic Plants, Lucknow, 226 015, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Raghvendra Pratap Singh
- Division of Crop Production and Protection, CSIR-Central Institute of Medicinal and Aromatic Plants, Lucknow, 226 015, India
| | - Ajay Taneja
- Department of Chemistry, Dr B.R. Ambedkar University, Agra, 282002, India
| | - Rahul Tiwari
- Department of Chemistry, Dr B.R. Ambedkar University, Agra, 282002, India
| | - Puja Khare
- Division of Crop Production and Protection, CSIR-Central Institute of Medicinal and Aromatic Plants, Lucknow, 226 015, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India.
| |
Collapse
|
13
|
Luo H, Zhong L. Ultraviolet germicidal irradiation (UVGI) for in-duct airborne bioaerosol disinfection: Review and analysis of design factors. BUILDING AND ENVIRONMENT 2021; 197:107852. [PMID: 33846664 PMCID: PMC8021448 DOI: 10.1016/j.buildenv.2021.107852] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 03/11/2021] [Accepted: 03/29/2021] [Indexed: 05/04/2023]
Abstract
The rapid increase in global cases of COVID-19 illness and death requires the implementation of appropriate and efficient engineering controls to improve indoor air quality. This paper focuses on the use of the ultraviolet germicidal irradiation (UVGI) air purification technology in HVAC ducts, which is particularly applicable to buildings where fully shutting down air recirculation is not feasible. Given the poor understanding of the in-duct UVGI system regarding its working mechanisms, designs, and applications, this review has the following key research objectives:•Identifying the critical parameters for designing a UVGI system, including the characterization of lamp output, behavior of the target microbial UV dose-response, and evaluation of the inactivation performance and energy consumption.•Elucidating the effects of environmental factors (air velocity, air temperature, and humidity) on the UVGI system design parameters and optimization of the in-duct UVGI design.•Summarizing existing UVGI system designs in the literature and illustrating their germicidal and energy performance in light of COVID-19 mitigation.
Collapse
Affiliation(s)
- Hao Luo
- Department of Mechanical Engineering, University of Alberta, 9211-116 Street NW, Edmonton, AB, T6G 1H9, Canada
| | - Lexuan Zhong
- Department of Mechanical Engineering, University of Alberta, 9211-116 Street NW, Edmonton, AB, T6G 1H9, Canada
| |
Collapse
|
14
|
Lai ACK, Nunayon SS. A new UVC-LED system for disinfection of pathogens generated by toilet flushing. INDOOR AIR 2021; 31:324-334. [PMID: 32989792 PMCID: PMC7537215 DOI: 10.1111/ina.12752] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 08/27/2020] [Accepted: 09/15/2020] [Indexed: 06/11/2023]
Abstract
A new disinfection system utilizing UVC-LED irradiation was developed. The system was affixed to the toilet seat, and it was challenged by three bacteria strains. Different configurations were tested: 3-LEDs, 5-LEDs (two variants), and 8-LEDs. To determine the arrangement designs of LEDs with the optimum efficacy, two variants of 5-LEDs configurations were additionally considered-uniform and concentrated (2-sided) distributions. It was noticed that disinfection efficacy initially increased with the number of LEDs, but with 8-LEDs, the trend became almost non-obvious for surface disinfection and just marginally increased for airborne disinfection. The mean efficiencies for the surface disinfection ranged from 55.17 ± 23.89% to 72.80 ± 4.13% for E. coli; 36.65 ± 2.99% to 50.05 ± 13.38% for S. typhimurium; and 8.81 ± 3.23% to 39.43 ± 9.33% for S. epidermidis. Likewise, the mean efficiencies for airborne disinfection ranged from 42.17 ± 8.18% to 70.70 ± 4.80%; 40.40 ± 17.90% to 58.31 ± 13.87%; and 24.16 ± 3.81% to 42.79 ± 10.20% for E. coli; S. typhimurium; and S. epidermidis, respectively. Furthermore, the efficacy of the uniform irradiation was nearly twice that of the concentrated irradiation for surface disinfection and 17.70% higher for airborne disinfection, when tested against E coli. Collectively, these very promising results showcased that this compact, sustainable, and localized disinfection system has a high potential for the next generation of disinfection devices.
Collapse
Affiliation(s)
- Alvin C. K. Lai
- Department of Architecture and Civil EngineeringCity University of Hong KongKowloon TongHong Kong
| | - Sunday S. Nunayon
- Department of Architecture and Civil EngineeringCity University of Hong KongKowloon TongHong Kong
| |
Collapse
|