Your browser doesn't support javascript.
Show: 20 | 50 | 100
Results 1 - 20 de 52
Filter
1.
MMWR Morb Mortal Wkly Rep ; 71(23): 770-775, 2022 Jun 10.
Article in English | MEDLINE | ID: covidwho-1887358

ABSTRACT

Effective COVID-19 prevention in kindergarten through grade 12 (K-12) schools requires multicomponent prevention strategies in school buildings and school-based transportation, including improving ventilation (1). Improved ventilation can reduce the concentration of infectious aerosols and duration of potential exposures (2,3), is linked to lower COVID-19 incidence (4), and can offer other health-related benefits (e.g., better measures of respiratory health, such as reduced allergy symptoms) (5). Whereas ambient wind currents effectively dissipate SARS-CoV-2 (the virus that causes COVID-19) outdoors,* ventilation systems provide protective airflow and filtration indoors (6). CDC examined reported ventilation improvement strategies among a nationally representative sample of K-12 public schools in the United States using wave 4 (February 14-March 27, 2022) data from the National School COVID-19 Prevention Study (NSCPS) (420 schools), a web-based survey administered to school-level administrators beginning in summer 2021.† The most frequently reported ventilation improvement strategies were lower-cost strategies, including relocating activities outdoors (73.6%), inspecting and validating existing heating, ventilation and air conditioning (HVAC) systems (70.5%), and opening doors (67.3%) or windows (67.2%) when safe to do so. A smaller proportion of schools reported more resource-intensive strategies such as replacing or upgrading HVAC systems (38.5%) or using high-efficiency particulate air (HEPA) filtration systems in classrooms (28.2%) or eating areas (29.8%). Rural and mid-poverty-level schools were less likely to report several resource-intensive strategies. For example, rural schools were less likely to use portable HEPA filtration systems in classrooms (15.6%) than were city (37.7%) and suburban schools (32.9%), and mid-poverty-level schools were less likely than were high-poverty-level schools to have replaced or upgraded HVAC systems (32.4% versus 48.8%). Substantial federal resources to improve ventilation in schools are available.§ Ensuring their use might reduce SARS-CoV-2 transmission in schools. Focusing support on schools least likely to have resource-intensive ventilation strategies might facilitate equitable implementation of ventilation improvements.


Subject(s)
Air Pollution, Indoor , COVID-19 , Air Conditioning , Air Pollution, Indoor/prevention & control , COVID-19/epidemiology , COVID-19/prevention & control , Humans , SARS-CoV-2 , Schools , United States/epidemiology , Ventilation
2.
PLoS One ; 17(4): e0266487, 2022.
Article in English | MEDLINE | ID: covidwho-1855007

ABSTRACT

Respiratory viruses are capable of transmitting via an aerosol route. Emerging evidence suggests that SARS-CoV-2 which causes COVID-19 can be spread through airborne transmission, particularly in indoor environments with poor ventilation. Heating, ventilation, and air conditioning (HVAC) systems can play a role in mitigating airborne virus transmission. Ultraviolet germicidal irradiation (UVGI), a feature that can be incorporated into HVAC systems, can be used to impede the ability of viruses to replicate and infect a host. We conducted a systematic review of the scientific literature examining the effectiveness of HVAC design features in reducing virus transmission-here we report results for ultraviolet (UV) radiation. We followed international standards for conducting systematic reviews and developed an a priori protocol. We conducted a comprehensive search to January 2021 of published and grey literature using Ovid MEDLINE, Compendex, and Web of Science Core. Two reviewers were involved in study selection, data extraction, and risk of bias assessments. We presented study characteristics and results in evidence tables, and synthesized results across studies narratively. We identified 32 relevant studies published between 1936 and 2020. Research demonstrates that: viruses and bacteriophages are inactivated by UV radiation; increasing UV dose is associated with decreasing survival fraction of viruses and bacteriophages; increasing relative humidity is associated with decreasing susceptibility to UV radiation; UV dose and corresponding survival fraction are affected by airflow pattern, air changes per hour, and UV device location; and UV radiation is associated with decreased transmission in both animal and human studies. While UV radiation has been shown to be effective in inactivating viruses and reducing disease transmission, practical implementation of UVGI in HVAC systems needs to consider airflow patterns, air changes per hour, and UV device location. The majority of the scientific literature is comprised of experimental, laboratory-based studies. Further, a variety of viruses have been examined; however, there are few studies of coronaviruses and none to date of SARS-CoV-2. Future field studies of UVGI systems could address an existing research gap and provide important information on system performance in real-world situations, particularly in the context of the current COVID-19 pandemic. This comprehensive synthesis of the scientific evidence examining the impact of UV radiation on virus transmission can be used to guide implementation of systems to mitigate airborne spread and identify priorities for future research. Trial registration PROSPERO 2020 CRD42020193968.


Subject(s)
Air Pollution, Indoor , COVID-19 , Air Conditioning , Heating , Humans , Pandemics/prevention & control , SARS-CoV-2 , Ultraviolet Rays , Ventilation
3.
PLoS One ; 16(11): e0257549, 2021.
Article in English | MEDLINE | ID: covidwho-1793615

ABSTRACT

Particulate generation occurs during exercise-induced exhalation, and research on this topic is scarce. Moreover, infection-control measures are inadequately implemented to avoid particulate generation. A laminar airflow ventilation system (LFVS) was developed to remove respiratory droplets released during treadmill exercise. This study aimed to investigate the relationship between the number of aerosols during training on a treadmill and exercise intensity and to elucidate the effect of the LFVS on aerosol removal during anaerobic exercise. In this single-center observational study, the exercise tests were performed on a treadmill at Running Science Lab in Japan on 20 healthy subjects (age: 29±12 years, men: 80%). The subjects had a broad spectrum of aerobic capacities and fitness levels, including athletes, and had no comorbidities. All of them received no medication. The exercise intensity was increased by 1-km/h increments until the heart rate reached 85% of the expected maximum rate and then maintained for 10 min. The first 10 subjects were analyzed to examine whether exercise increased the concentration of airborne particulates in the exhaled air. For the remaining 10 subjects, the LFVS was activated during constant-load exercise to compare the number of respiratory droplets before and after LFVS use. During exercise, a steady amount of particulates before the lactate threshold (LT) was followed by a significant and gradual increase in respiratory droplets after the LT, particularly during anaerobic exercise. Furthermore, respiratory droplets ≥0.3 µm significantly decreased after using LFVS (2120800±759700 vs. 560 ± 170, p<0.001). The amount of respiratory droplets significantly increased after LT. The LFVS enabled a significant decrease in respiratory droplets during anaerobic exercise in healthy subjects. This study's findings will aid in exercising safely during this pandemic.


Subject(s)
Air Conditioning/methods , COVID-19/prevention & control , Exercise/physiology , Particulate Matter/chemistry , Adult , Aerosols/chemistry , Air Filters , Anaerobic Threshold/physiology , COVID-19/metabolism , Exercise Test/methods , Exhalation/physiology , Female , Heart Rate/physiology , Humans , Japan , Lactic Acid/metabolism , Male , Oxygen Consumption/physiology , Respiration , Respiratory System/physiopathology , Running/physiology , SARS-CoV-2/pathogenicity , Ventilation/methods
4.
Int J Environ Res Public Health ; 19(6)2022 03 16.
Article in English | MEDLINE | ID: covidwho-1760587

ABSTRACT

Indoor air quality in hospital operating rooms is of great concern for the prevention of surgical site infections (SSI). A wide range of relevant medical and engineering literature has shown that the reduction in air contamination can be achieved by introducing a more efficient set of controls of HVAC systems and exploiting alarms and monitoring systems that allow having a clear report of the internal air status level. In this paper, an operating room air quality monitoring system based on a fuzzy decision support system has been proposed in order to help hospital staff responsible to guarantee a safe environment. The goal of the work is to reduce the airborne contamination in order to optimize the surgical environment, thus preventing the occurrence of SSI and reducing the related mortality rate. The advantage of FIS is that the evaluation of the air quality is based on easy-to-find input data established on the best combination of parameters and level of alert. Compared to other literature works, the proposed approach based on the FIS has been designed to take into account also the movement of clinicians in the operating room in order to monitor unauthorized paths. The test of the proposed strategy has been executed by exploiting data collected by ad-hoc sensors placed inside a real operating block during the experimental activities of the "Bacterial Infections Post Surgery" Project (BIPS). Results show that the system is capable to return risk values with extreme precision.


Subject(s)
Air Pollution, Indoor , Operating Rooms , Air Conditioning , Air Microbiology , Air Pollution, Indoor/analysis , Air Pollution, Indoor/prevention & control , Humans , Surgical Wound Infection/prevention & control
5.
Int J Environ Res Public Health ; 19(3)2022 01 29.
Article in English | MEDLINE | ID: covidwho-1667146

ABSTRACT

Improving indoor air quality present in environments where people live is important to protect human health. This particularly applies to public transportation, where air quality may affect the health and safety of passengers, workers and staff. To provide better air quality, many buildings and transports are provided with heating, ventilation and air conditioning (HVAC) systems, which are always equipped with filters to retain the particulate present in the airflow, but they lack continuous air sanitization systems. In this study, a new UV-C LED and ionizer-based continuous sanitation air (CSA) system to be installed in a train HVAC was developed (international patent: N.PCT/IB2021/054194) and its sanitation efficacy against various microbial species (bacteria and fungi) was assessed. The device proved to be very effective at the microbial killing of aerodispersed microorganisms, both in its experimental configuration (ISO 15714:2019) and in a train setting. The installation of this CSA system on public transportation appears to be a promising solution to guarantee high microbiological air quality with a very low environmental impact due to its eco-friendly components.


Subject(s)
Air Pollution, Indoor , Sanitation , Air Conditioning , Air Pollution, Indoor/analysis , Heating , Humans , Ventilation
6.
Int J Environ Res Public Health ; 19(3)2022 01 29.
Article in English | MEDLINE | ID: covidwho-1667139

ABSTRACT

A cross-layer non-vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) occurred in a quarantine hotel in Guangzhou, Guangdong Province, China in June 2021. To explore the cross-layer transmission path and influencing factors of viral aerosol, we set up different scenarios to carry out simulation experiments. The results showed that the air in the polluted room can enter the corridor by opening the door to take food and move out the garbage, then mix with the fresh air taken from the outside as part of the air supply of the central air conditioning system and re-enter into different rooms on the same floor leading to the same-layer transmission. In addition, flushing the toilet after defecation and urination will produce viral aerosol that pollutes rooms on different floors through the exhaust system and the vertical drainage pipe in the bathroom, resulting in cross-layer vertical transmission, also aggravating the transmission in different rooms on the same floor after mixing with the air of the room and entering the corridor to become part of the air supply, and meanwhile, continuing to increase the cross-layer transmission through the vertical drainage pipe. Therefore, the air conditioning and ventilation system of the quarantine hotel should be operated in full fresh air mode and close the return air; the exhaust volume of the bathroom should be greater than the fresh air volume. The exhaust pipe of the bathroom should be independently set and cannot be interconnected or connected in series. The riser of the sewage and drainage pipeline of the bathroom should maintain vertical to exhaust independently and cannot be arbitrarily changed to horizontal pipe assembly.


Subject(s)
COVID-19 , SARS-CoV-2 , Aerosols , Air Conditioning , Humans , Quarantine
7.
PLoS One ; 16(12): e0259996, 2021.
Article in English | MEDLINE | ID: covidwho-1592627

ABSTRACT

OBJECTIVES: To evaluate (1) the relationship between heating, ventilation, and air conditioning (HVAC) systems and bioaerosol concentrations in hospital rooms, and (2) the effectiveness of laminar air flow (LAF) and high efficiency particulate air (HEPA) according to the indoor bioaerosol concentrations. METHODS: Databases of Embase, PubMed, Cochrane Library, MEDLINE, and Web of Science were searched from 1st January 2000 to 31st December 2020. Two reviewers independently extracted data and assessed the quality of the studies. The samples obtained from different areas of hospitals were grouped and described statistically. Furthermore, the meta-analysis of LAF and HEPA were performed using random-effects models. The methodological quality of the studies included in the meta-analysis was assessed using the checklist recommended by the Agency for Healthcare Research and Quality. RESULTS: The mean CFU/m3 of the conventional HVAC rooms and enhanced HVAC rooms was lower than that of rooms without HVAC systems. Furthermore, the use of the HEPA filter reduced bacteria by 113.13 (95% CI: -197.89, -28.38) CFU/m3 and fungi by 6.53 (95% CI: -10.50, -2.55) CFU/m3. Meanwhile, the indoor bacterial concentration of LAF systems decreased by 40.05 (95% CI: -55.52, -24.58) CFU/m3 compared to that of conventional HVAC systems. CONCLUSIONS: The HVAC systems in hospitals can effectively remove bioaerosols. Further, the use of HEPA filters is an effective option for areas that are under-ventilated and require additional protection. However, other components of the LAF system other than the HEPA filter are not conducive to removing airborne bacteria and fungi. LIMITATION OF STUDY: Although our study analysed the overall trend of indoor bioaerosols, the conclusions cannot be extrapolated to rare, hard-to-culture, and highly pathogenic species, as well as species complexes. These species require specific culture conditions or different sampling requirements. Investigating the effects of HVAC systems on these species via conventional culture counting methods is challenging and further analysis that includes combining molecular identification methods is necessary. STRENGTH OF THE STUDY: Our study was the first meta-analysis to evaluate the effect of HVAC systems on indoor bioaerosols through microbial incubation count. Our study demonstrated that HVAC systems could effectively reduce overall bioaerosol concentrations to maintain better indoor air quality. Moreover, our study provided further evidence that other components of the LAF system other than the HEPA filter are not conducive to removing airborne bacteria and fungi. PRACTICAL IMPLICATION: Our research showed that HEPA filters are more effective at removing bioaerosols in HVAC systems than the current LAF system. Therefore, instead of opting for the more costly LAF system, a filter with a higher filtration rate would be a better choice for indoor environments that require higher air quality; this is valuable for operating room construction and maintenance budget allocation.


Subject(s)
Air Conditioning/instrumentation , Air Pollution, Indoor/prevention & control , Environmental Monitoring/methods , Filtration/standards , Heating/instrumentation , Hospitals/standards , Ventilation/instrumentation , Air Pollution, Indoor/analysis , Environmental Monitoring/instrumentation , Equipment and Supplies, Hospital , Humans
8.
Viruses ; 13(12)2021 12 17.
Article in English | MEDLINE | ID: covidwho-1580426

ABSTRACT

There is strong evidence associating the indoor environment with transmission of SARS-CoV-2, the virus that causes COVID-19. SARS-CoV-2 can spread by exposure to droplets and very fine aerosol particles from respiratory fluids that are released by infected persons. Layered mitigation strategies, including but not limited to maintaining physical distancing, adequate ventilation, universal masking, avoiding overcrowding, and vaccination, have shown to be effective in reducing the spread of SARS-CoV-2 within the indoor environment. Here, we examine the effect of mitigation strategies on reducing the risk of exposure to simulated respiratory aerosol particles within a classroom-style meeting room. To quantify exposure of uninfected individuals (Recipients), surrogate respiratory aerosol particles were generated by a breathing simulator with a headform (Source) that mimicked breath exhalations. Recipients, represented by three breathing simulators with manikin headforms, were placed in a meeting room and affixed with optical particle counters to measure 0.3-3 µm aerosol particles. Universal masking of all breathing simulators with a 3-ply cotton mask reduced aerosol exposure by 50% or more compared to scenarios with simulators unmasked. While evaluating the effect of Source placement, Recipients had the highest exposure at 0.9 m in a face-to-face orientation. Ventilation reduced exposure by approximately 5% per unit increase in air change per hour (ACH), irrespective of whether increases in ACH were by the HVAC system or portable HEPA air cleaners. The results demonstrate that mitigation strategies, such as universal masking and increasing ventilation, reduce personal exposure to respiratory aerosols within a meeting room. While universal masking remains a key component of a layered mitigation strategy of exposure reduction, increasing ventilation via system HVAC or portable HEPA air cleaners further reduces exposure.


Subject(s)
Air Pollution, Indoor/prevention & control , Inhalation Exposure/prevention & control , Masks , Physical Distancing , Ventilation , Air Conditioning , COVID-19/prevention & control , Humans , SARS-CoV-2/isolation & purification
9.
PLoS One ; 16(11): e0257549, 2021.
Article in English | MEDLINE | ID: covidwho-1511814

ABSTRACT

Particulate generation occurs during exercise-induced exhalation, and research on this topic is scarce. Moreover, infection-control measures are inadequately implemented to avoid particulate generation. A laminar airflow ventilation system (LFVS) was developed to remove respiratory droplets released during treadmill exercise. This study aimed to investigate the relationship between the number of aerosols during training on a treadmill and exercise intensity and to elucidate the effect of the LFVS on aerosol removal during anaerobic exercise. In this single-center observational study, the exercise tests were performed on a treadmill at Running Science Lab in Japan on 20 healthy subjects (age: 29±12 years, men: 80%). The subjects had a broad spectrum of aerobic capacities and fitness levels, including athletes, and had no comorbidities. All of them received no medication. The exercise intensity was increased by 1-km/h increments until the heart rate reached 85% of the expected maximum rate and then maintained for 10 min. The first 10 subjects were analyzed to examine whether exercise increased the concentration of airborne particulates in the exhaled air. For the remaining 10 subjects, the LFVS was activated during constant-load exercise to compare the number of respiratory droplets before and after LFVS use. During exercise, a steady amount of particulates before the lactate threshold (LT) was followed by a significant and gradual increase in respiratory droplets after the LT, particularly during anaerobic exercise. Furthermore, respiratory droplets ≥0.3 µm significantly decreased after using LFVS (2120800±759700 vs. 560 ± 170, p<0.001). The amount of respiratory droplets significantly increased after LT. The LFVS enabled a significant decrease in respiratory droplets during anaerobic exercise in healthy subjects. This study's findings will aid in exercising safely during this pandemic.


Subject(s)
Air Conditioning/methods , COVID-19/prevention & control , Exercise/physiology , Particulate Matter/chemistry , Adult , Aerosols/chemistry , Air Filters , Anaerobic Threshold/physiology , COVID-19/metabolism , Exercise Test/methods , Exhalation/physiology , Female , Heart Rate/physiology , Humans , Japan , Lactic Acid/metabolism , Male , Oxygen Consumption/physiology , Respiration , Respiratory System/physiopathology , Running/physiology , SARS-CoV-2/pathogenicity , Ventilation/methods
10.
Am J Infect Control ; 50(3): 330-335, 2022 03.
Article in English | MEDLINE | ID: covidwho-1474275

ABSTRACT

BACKGROUND: The COVID-19 pandemic affected universities and institutions and caused campus shutdowns with a transition to online teaching models. To detect infections that might spread on campus, we pursued research towards detecting SARS-CoV-2 in air samples inside student dorms. METHODS: We sampled air in 2 large dormitories for 3.5 months and a separate isolation suite containing a student who had tested positive for COVID-19. We developed novel techniques employing 4 methods to collect air samples: Filter Cassettes, Button Sampler, BioSampler, and AerosolSense sampler combined with direct qRT-PCR SARS-CoV-2 analysis. RESULTS: For the 2 large dorms with the normal student population, we detected SARS-CoV-2 in 11 samples. When compared with student nasal swab qRT-PCR testing, we detected SARS-CoV-2 in air samples when a PCR positive COVID-19 student was living on the same floor of the sampling location with a detection rate of 75%. For the isolation dorm, we had a 100% SARS-CoV-2 detection rate with AerosolSense sampler. CONCLUSIONS: Our data suggest air sampling may be an important SARS-CoV-2 surveillance technique, especially for buildings with congregant living settings (dorms, correctional facilities, barracks). Future building designs and public health policies should consider implementation of Heating, Ventilation, and Air Conditioning surveillance.


Subject(s)
COVID-19 , SARS-CoV-2 , Air Conditioning , COVID-19/diagnosis , Heating , Humans , Pandemics , Students
11.
PLoS Comput Biol ; 17(10): e1009474, 2021 10.
Article in English | MEDLINE | ID: covidwho-1477508

ABSTRACT

The role of heating, ventilation, and air-conditioning (HVAC) systems in the transmission of SARS-CoV-2 is unclear. To address this gap, we simulated the release of SARS-CoV-2 in a multistory office building and three social gathering settings (bar/restaurant, nightclub, wedding venue) using a well-mixed, multi-zone building model similar to those used by Wells, Riley, and others. We varied key factors of HVAC systems, such as the Air Changes Per Hour rate (ACH), Fraction of Outside Air (FOA), and Minimum Efficiency Reporting Values (MERV) to examine their effect on viral transmission, and additionally simulated the protective effects of in-unit ultraviolet light decontamination (UVC) and separate in-room air filtration. In all building types, increasing the ACH reduced simulated infections, and the effects were seen even with low aerosol emission rates. However, the benefits of increasing the fraction of outside air and filter efficiency rating were greatest when the aerosol emission rate was high. UVC filtration improved the performance of typical HVAC systems. In-room filtration in an office setting similarly reduced overall infections but worked better when placed in every room. Overall, we found little evidence that HVAC systems facilitate SARS-CoV-2 transmission; most infections in the simulated office occurred near the emission source, with some infections in individuals temporarily visiting the release zone. HVAC systems only increased infections in one scenario involving a marginal increase in airflow in a poorly ventilated space, which slightly increased the likelihood of transmission outside the release zone. We found that improving air circulation rates, increasing filter MERV rating, increasing the fraction of outside air, and applying UVC radiation and in-room filtration may reduce SARS-CoV-2 transmission indoors. However, these mitigation measures are unlikely to provide a protective benefit unless SARS-CoV-2 aerosol emission rates are high (>1,000 Plaque-forming units (PFU) / min).


Subject(s)
Air Conditioning , COVID-19/transmission , Heating , SARS-CoV-2 , Ventilation , Aerosols , Air Microbiology , Air Movements , COVID-19/prevention & control , COVID-19/virology , Computational Biology , Computer Simulation , Humans , Models, Biological , Pandemics , SARS-CoV-2/radiation effects , Social Interaction , Ultraviolet Rays , Workplace
12.
BMJ Open ; 11(10): e047772, 2021 10 12.
Article in English | MEDLINE | ID: covidwho-1462954

ABSTRACT

OBJECTIVES: In COVID-19, transfer of respiratory materials transmits disease and drives the pandemic but the interplay of droplet and aerosol physics, physiology and environment is not fully understood. To advance understanding of disease transmission mechanisms and to find novel exposure minimisation strategies, we studied cough-driven material transport modes and the efficacy of control strategies. DESIGN: Computer simulations and real-world experiments were used for integrating an intensive care setting, multiphysics and physiology. Patient-focused airflow management and air purification strategies were examined computationally and validated by submicron particle exhalation imaging in volunteers. SETTING: Hospital setting during a respiratory virus pandemic with transmission by respiratory droplets and aerosols. PARTICIPANTS: Healthy volunteers. OUTCOME MEASURES: Distribution of, and exposure to, potentially infectious respiratory secretions. RESULTS: Respiratory materials ejected by cough exhibited four transport modes: long-distance ballistic, short-distance ballistic, 'jet rider' and aerosol modes. Interaction with air conditioning driven flow contaminated a hospital room rapidly. Different than large droplets or aerosols, jet rider droplets travelled with the turbulent air jet initially, but fell out at a distance, were not well eliminated by air conditioning and exposed bystanders at larger distance and longer time; their size predisposes them to preferential capture in the nasal mucosa, the primordial COVID-19 infection site. 'Cough shields' captured large droplets but induced lateral dispersion of aerosols and jet riders. An air purification device alone had limited efficacy. A 'Shield and Sink' approach combining cough shields with 'virus sinks' minimised exposure to all secretions in modelling and real-life experiments. CONCLUSIONS: Jet riders have characteristics of highly efficient respiratory infection vectors and may play a role in COVID-19 transmission. Exposure to all droplet types can be minimised through an easily implemented Shield and Sink strategy.


Subject(s)
Air Conditioning , COVID-19 , Aerosols , Hospitals , Humans , SARS-CoV-2
13.
J Hosp Infect ; 119: 163-169, 2022 Jan.
Article in English | MEDLINE | ID: covidwho-1433519

ABSTRACT

BACKGROUND: While the range of possible transmission pathways of severe acute respiratory syndrome coronavirus-2 in various settings has been investigated thoroughly, most authorities have recently acknowledged the role of aerosol spread in its transmission, especially in indoor environments where ventilation is poor. Engineering controls are needed to mitigate aerosol transmission in high-risk settings including hospital wards, classrooms and offices. AIM: To assess the effectiveness of aerosol filtration by portable air cleaning devices with high-efficiency particulate air filters used in addition to a standard building heating ventilation and air conditioning (HVAC) system. METHODS: Test rooms, including a single-bed hospital room, were filled with test aerosol to simulate aerosol movement. Aerosol counts were measured over time with various portable air cleaning devices and room ventilation systems to quantify the overall aerosol clearance rate. FINDINGS: Portable air cleaning devices were very effective for removal of aerosols. The aerosols were cleared five times faster in a small control room with portable air cleaning devices than in the room with HVAC alone. The single-bed hospital room had an excellent ventilation rate (∼14 air changes per hour) and cleared the aerosols in 20 min. However, with the addition of two air cleaning devices, the clearance time was three times faster. CONCLUSIONS: Inexpensive portable air cleaning devices should be considered for small and enclosed spaces in healthcare settings, such as inpatient rooms and personal protective equipment donning/doffing stations. Portable air cleaning devices are particularly important where there is limited ability to reduce aerosol transmission with building HVAC ventilation.


Subject(s)
Air Pollution, Indoor , COVID-19 , Aerosols , Air Conditioning , Filtration , Humans , SARS-CoV-2 , Ventilation
14.
Sci Total Environ ; 804: 150249, 2022 Jan 15.
Article in English | MEDLINE | ID: covidwho-1401854

ABSTRACT

Occupancy schedules and density can have a substantial influence on building plug, lighting, and air conditioning energy usage. In recent years, the study related to occupancy and its impact on building energy consumption has gained momentum and is also promoted by ASHRAE as it has created a multi-disciplinary group to encourage a comprehensive study of occupant behaviour in buildings. Past studies suggest that building systems do not consume the same energy and provide similar Indoor Environmental Quality (IEQ) to their designed specifications due to inaccurate assumptions of occupants and their behaviour. Supplying ASHRAE 62.1 specified minimum required ventilation based on accurate occupancy may lead to significant air-conditioning energy savings. However, the same strategy is not suitable in the current time since minimum required ventilation may not be sufficient to mitigate the SARS-CoV-2 virus spread in confined spaces. High-temperature cooling augmented with elevated air movement across an acceptable range of velocity can maintain the health and comfort of occupants by providing higher ventilation and without an energy penalty. The analysis of the literature highlights strengths, weaknesses, and key observations about the existing occupancy monitoring and occupancy-based building system control methods to help in the direction of future occupancy-based research.


Subject(s)
Air Pollution, Indoor , COVID-19 , Air Conditioning , Humans , SARS-CoV-2 , Ventilation
15.
ACS Nano ; 14(7): 7704-7713, 2020 07 28.
Article in English | MEDLINE | ID: covidwho-1387152

ABSTRACT

We advocate the widespread use of UV-C light as a short-term, easily deployable, and affordable way to limit virus spread in the current SARS-CoV-2 pandemic. Radical social distancing with the associated shutdown of schools, restaurants, sport clubs, workplaces, and traveling has been shown to be effective in reducing virus spread, but its economic and social costs are unsustainable in the medium term. Simple measures like frequent handwashing, facial masks, and other physical barriers are being commonly adopted to prevent virus transmission. However, their efficacy may be limited, particularly in shared indoor spaces, where, in addition to airborne transmission, elements with small surface areas such as elevator buttons, door handles, and handrails are frequently used and can also mediate transmission. We argue that additional measures are necessary to reduce virus transmission when people resume attending schools and jobs that require proximity or some degree of physical contact. Among the available alternatives, UV-C light satisfies the requirements of rapid, widespread, and economically viable deployment. Its implementation is only limited by current production capacities, an increase of which requires swift intervention by industry and authorities.


Subject(s)
Air Conditioning/standards , Coronavirus Infections/transmission , Disease Transmission, Infectious/prevention & control , Disinfection/methods , Heating/standards , Pneumonia, Viral/transmission , Ventilation/standards , Air Conditioning/adverse effects , COVID-19 , Confined Spaces , Coronavirus Infections/epidemiology , Heating/adverse effects , Humans , Pandemics , Pneumonia, Viral/epidemiology , Transportation/standards , Ultraviolet Rays
16.
Environ Sci Pollut Res Int ; 28(40): 56376-56391, 2021 Oct.
Article in English | MEDLINE | ID: covidwho-1384555

ABSTRACT

It is important to know whether SARS-CoV-2 is spread through the air conditioning systems. Taking the central air conditioning system as an example, we analyze the mechanism and potential health risk of respiratory virus transmission in air-conditioned rooms and propose a method to study the risk of virus transmission in central air conditioning systems by investigating the data from medical experiments. The virus carrying capacity and the decay characteristics of indoor pathogen droplets are studied in this research. Additionally, the effects of air temperature and relative humidity on the virus survival in the air or on surfaces are investigated. The removal efficiency of infectious droplet nuclei by using an air conditioning filter was then determined. Thus, the transmission risk during the operation of the centralized air conditioning system is evaluated. The results show that the indoor temperature and humidity are controlled in the range of 20-25 °C and 40-70% by central air conditioning during the epidemic period, which not only benefits the health and comfort of residents, but also weakens the vitality of the virus. The larger the droplet size, the longer the viruses survive. Since the filter efficiency of the air conditioning filter increases with the increase in particle size, increasing the number of air changes of the circulating air volume can accelerate the removal of potential pathogen particles. Therefore, scientific operation of centralized air conditioning systems during the epidemic period has more advantages than disadvantages.


Subject(s)
Air Conditioning , Air Pollution, Indoor , COVID-19 , Viruses , Air Microbiology , Air Pollution, Indoor/analysis , COVID-19/transmission , Humans , Humidity , SARS-CoV-2 , Virus Diseases/transmission
17.
Indoor Air ; 32(1): e12917, 2022 01.
Article in English | MEDLINE | ID: covidwho-1388295

ABSTRACT

Tracer gas experiments were conducted in a 158 m3 room with overhead supply diffusers to study dispersion of contaminants from simulated speaking in physically distanced meeting and classroom configurations. The room was contained within a 237 m3 cell with open plenum return to the HVAC system. Heated manikins at desks and a researcher operating the tracer release apparatus presented 8-9 thermal plumes. Experiments were conducted under conditions of no forced air and neutral, cooled, or heated air supplied at 980-1100 cmh, and with/out 20% outdoor air. CO2 was released at the head of one manikin in each experiment to simulate small (<5 µm diameter) respiratory aerosols. The metric of exposure relative to perfectly mixed (ERM) is introduced to quantify impacts, based on measurements at manikin heads and at three heights in the center and corners of the room. Chilled or neutral supply air provided good mixing with ERMs close to one. Thermal stratification during heating produced higher ERMs at most manikins: 25% were ≥2.5 and the highest were >5× perfectly mixed conditions. Operation of two within-zone air cleaners together moving ≥400 cmh vertically in the room provided enough mixing to mitigate elevated exposure variations.


Subject(s)
Air Pollution, Indoor , Ventilation , Air Conditioning , Air Movements , Heating
18.
Environ Res ; 203: 111765, 2022 01.
Article in English | MEDLINE | ID: covidwho-1330806

ABSTRACT

COVID-19 forced the human population to rethink its way of living. The threat posed by the potential spread of the virus via an airborne transmission mode through ventilation systems in buildings and enclosed spaces has been recognized as a major concern. To mitigate this threat, researchers have explored different technologies and methods that can remove or decrease the concentration of the virus in ventilation systems and enclosed spaces. Although many technologies and methods have already been researched, some are currently available on the market, but their effectiveness and safety concerns have not been fully investigated. To acquire a broader view and collective perspective of the current research and development status, this paper discusses a comprehensive review of various workable technologies and methods to combat airborne viruses, e.g., COVID-19, in ventilation systems and enclosed spaces. These technologies and methods include an increase in ventilation, high-efficiency air filtration, ionization of the air, environmental condition control, ultraviolet germicidal irradiation, non-thermal plasma and reactive oxygen species, filter coatings, chemical disinfectants, and heat inactivation. Research gaps have been identified and discussed, and recommendations for applying such technologies and methods have also been provided in this article.


Subject(s)
COVID-19 , Air Conditioning , Humans , Probability , SARS-CoV-2 , Ventilation
19.
PLoS One ; 16(7): e0255051, 2021.
Article in English | MEDLINE | ID: covidwho-1327979

ABSTRACT

At present, people are demanding better indoor air quality during the COVID-19 pandemic. In addition to maintaining the basic functions, new air-conditioning should also add air purification functions to improve indoor air quality and reduce the possibility of virus transmission. Nowadays, there is lack of research results on the innovation of air-conditioning. The aim of this study is to present a two-stage mathematical model for identifying critical manufacturing factors in the innovation process of air conditioning. In this paper, Kano and quality function deployment (QFD) are used to analyze the critical factors affecting air-conditioning innovation. Some studies have proposed using Kano-QFD model to analyze product innovation, but the study only studies one stage, which loses the analysis of the subsequent stages of product innovation. Based on this, this paper studies the priority method of two-stage critical factors for air-conditioning innovation. Firstly, the questionnaire survey and fuzzy sets are used to collect demand information of multi-agent (customers and professional technicians). Secondly, the Kano model is used to classify and calculate satisfaction of multi-agent. Then, QFD is used to transform multi-agent demands into engineering property indexes (first stage) and technical property indexes (second stage) and calculate the weight of each index. Finally, the applicability and superiority of this method is illustrated by taking the central air-conditioning as an example.


Subject(s)
Air Conditioning , Air Microbiology , COVID-19/epidemiology , Filtration/instrumentation , Models, Theoretical , Pandemics , COVID-19/prevention & control , COVID-19/transmission , Fuzzy Logic
20.
Environ Int ; 157: 106774, 2021 12.
Article in English | MEDLINE | ID: covidwho-1322094

ABSTRACT

To identify potential countermeasures for coronavirus disease (COVID-19), we determined the air exchange rates in stationary and moving train cars under various conditions in July, August, and December 2020 in Japan. When the doors were closed, the air exchange rates in both stationary and moving trains increased with increasing area of window-opening (0.23-0.78/h at 0 m2, windows closed to 2.1-10/h at 2.86 m2, fully open). The air exchange rates were one order of magnitude higher when doors were open than when closed. With doors closed, the air exchange rates were higher when the centralized air conditioning (AC) and crossflow fan systems (fan) were on than when off. The air exchange rates in moving trains increased as train speed increased, from 10/h at 20 km/h to 42/h at 57 km/h. Air exchange rates did not differ significantly between empty cars and those filled with 230 mannequins representing commuters. The air exchange rates were lower during aboveground operation than during underground. Assuming that 30-300 passengers travel in a train car for 7-60 min and that the community infection rate is 0.0050-0.30%, we estimated that commuters' infection risk on trains was reduced by 91-94% when all 12 windows were opened (to a height of 10 cm) and the AC/fan was on compared with that when windows were closed and the AC/fan was off.


Subject(s)
Air Microbiology , Air Pollution, Indoor , COVID-19 , Railroads , Ventilation , Air Conditioning , COVID-19/transmission , Humans , SARS-CoV-2
SELECTION OF CITATIONS
SEARCH DETAIL