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1.
J Occup Environ Hyg ; 19(5): 327-334, 2022 05.
Article in English | MEDLINE | ID: covidwho-1764436

ABSTRACT

A company COVID-19 Heating, Ventilation, and Air Conditioning Guideline was implemented globally, as part of a larger control measure toolset, to minimize the potential for SARS-CoV-2 aerosol transmission. The COVID-19 Heating, Ventilation, and Air Conditioning Guideline informed and provided the process to optimize existing ventilation systems, set occupancy duration limits, and set clearance periods for a given space. Aerosol transmission modeling was used extensively to determine space limitations to reduce the potential for aerosol transmission in various manufacturing, lab, warehouse, aircraft, and administrative workspaces. This paper focuses on the modeling completed for administrative spaces (e.g., offices, conference rooms, restrooms, elevators) due to their lower ventilation rates, higher occupant densities, and greater vocalization levels. A detailed description of how the Guideline was implemented, with examples showing the evaluation and determinations made for specific spaces, is provided. World-wide implementation of this Guideline, as one of the layers of protection, was a key component in the overall strategy to reduce aerosol transmission of the SARS-CoV-2 virus.


Subject(s)
Air Pollution, Indoor , COVID-19 , Aerosols , Air Pollution, Indoor/prevention & control , Humans , SARS-CoV-2 , Ventilation
2.
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
3.
J Occup Environ Hyg ; 19(5): 295-301, 2022 05.
Article in English | MEDLINE | ID: covidwho-1740663

ABSTRACT

Ventilation plays an important role in mitigating the risk of airborne virus transmission in university classrooms. During the early phase of the COVID-19 pandemic, methods to assess classrooms for ventilation adequacy were needed. The aim of this paper was to compare the adequacy of classroom ventilation determined through an easily accessible, simple, quantitative measure of air changes per hour (ACH) to that determined through qualitative "expert judgment" and recommendations from the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), and the American Conference of Governmental Industrial Hygienists (ACGIH)®. Two experts, ventilation engineers from facilities maintenance, qualitatively ranked buildings with classrooms on campus with regard to having "acceptable classroom ventilation." Twelve lecture classrooms were selected for further testing, including a mix of perceived adequate/inadequate ventilation. Total air change per hour (ACH) was measured to quantitatively assess ventilation through the decay of carbon dioxide in the front and rear of these classrooms. The outdoor ACH was calculated by multiplying the total ACH by the outdoor air fraction. The classrooms in a building designed to the highest ASHRAE standards (62.1 2004) did not meet ACGIH COVID-19 recommendations. Four of the classrooms met the ASHRAE criteria. However, a classroom that was anticipated to fail based on expert knowledge met the ASHRAE and ACGIH criteria. Only two classrooms passed stringent ACGIH recommendations (outdoor ACH > 6). None of the classrooms that passed ACGIH criteria were originally expected to pass. There was no significant difference in ACH measured in the front and back of classrooms, suggesting that all classrooms were well mixed with no dead zones. From these results, schools should assess classroom ventilation considering a combination of classroom design criteria, expert knowledge, and ACH measurements.


Subject(s)
Air Pollution, Indoor , COVID-19 , Air Pollution, Indoor/prevention & control , COVID-19/epidemiology , Humans , Pandemics , Schools , Universities , Ventilation/methods
4.
J Occup Environ Hyg ; 19(5): 310-317, 2022 05.
Article in English | MEDLINE | ID: covidwho-1740662

ABSTRACT

The purpose of this study was to determine if strategic placement of portable air purifiers would improve effectiveness of aerosol reduction in a space as compared to use as a general room air purifier. Two sizes of portable air purifiers were placed in two different positions intended to function similar to either a local exhaust ventilation hood or an air curtain to determine if strategic placement would lead to a reduction of particles in a worker's position at a desk in an office environment. Particle generators were used to introduce particulate into the air and personal aerosol monitors measured particles during each test condition. Results showed that when the medium room portable air purifiers used in this study were set to high, corresponding to 98 CFM, and placed near the breathing zone of each office worker with the unit's filter cover removed, the particle concentration was reduced 35% beyond the reduction that would be expected if the same units were placed on the floor behind the occupant's workstation. Results also indicated that the larger portable air purifier tested, positioned as close as reasonable to each occupant's breathing zone with the largest capture area possible (i.e., removing the unit's filter cover), delivers the best aerosol reduction performance. The authors concluded that as a layer of protection against transmission of airborne infectious organisms for office occupants, installing a portable air purifier, sized and operated similar to the units tested in this study on the desk 12 inches from the breathing zone of the worker, has the potential to reduce airborne particulate to a greater degree than if the same units were placed outside of the breathing zone, in the general cubicle area.


Subject(s)
Air Filters , Air Pollution, Indoor , COVID-19 , Aerosols , Air Pollution, Indoor/prevention & control , COVID-19/prevention & control , Humans , Vehicle Emissions , Ventilation
5.
Int J Environ Res Public Health ; 19(5)2022 Mar 03.
Article in English | MEDLINE | ID: covidwho-1732012

ABSTRACT

Due to the current COVID-19 pandemic, guaranteeing thermal comfort and low CO2 levels in classrooms through efficient ventilation has become vitally important. This study presents three-dimensional simulations based on computational fluid dynamics of airflow inside an air-conditioned classroom located in Veracruz, Mexico. The analysis included various positions of an air extractor, Reynolds numbers up to 3.5 × 104, four different concentrations of pollutant sources, and three different times of the day. The simulations produced velocity, air temperature, and CO2 concentrations fields, and we calculated average air temperatures, average CO2 concentrations, and overall ventilation effectiveness. Our results revealed an optimal extractor position and Reynolds number conducive to thermal comfort and low CO2 levels due to an adequate ventilation configuration. At high pollutant concentrations, it is necessary to reduce the number of students in the classroom to achieve safe CO2 levels.


Subject(s)
Air Pollution, Indoor , COVID-19 , Air Pollution, Indoor/analysis , Air Pollution, Indoor/prevention & control , COVID-19/epidemiology , Carbon Dioxide/analysis , Humans , Pandemics , SARS-CoV-2
6.
Indoor Air ; 32(2): e12989, 2022 02.
Article in English | MEDLINE | ID: covidwho-1714193

ABSTRACT

To optimize strategies for curbing the transmission of airborne pathogens, the efficacy of three key controls-face masks, ventilation, and physical distancing-must be well understood. In this study, we used the Quadrature-based model of Respiratory Aerosol and Droplets to quantify the reduction in exposure to airborne pathogens from various combinations of controls. For each combination of controls, we simulated thousands of scenarios that represent the tremendous variability in factors governing airborne transmission and the efficacy of mitigation strategies. While the efficacy of any individual control was highly variable among scenarios, combining universal mask-wearing with distancing of 1 m or more reduced the median exposure by more than 99% relative to a close, unmasked conversation, with further reductions if ventilation is also enhanced. The large reductions in exposure to airborne pathogens translated to large reductions in the risk of initial infection in a new host. These findings suggest that layering controls is highly effective for reducing transmission of airborne pathogens and will be critical for curbing outbreaks of novel viruses in the future.


Subject(s)
Air Microbiology , Air Pollution, Indoor , COVID-19 , Aerosols , Air Pollution, Indoor/prevention & control , COVID-19/prevention & control , Humans , SARS-CoV-2 , Ventilation
7.
Indoor Air ; 32(2): e12987, 2022 02.
Article in English | MEDLINE | ID: covidwho-1714191

ABSTRACT

To limit community spread of SARS-CoV-2, CDC recommends universal masking indoors, maintaining 1.8 m of physical distancing, adequate ventilation, and avoiding crowded indoor spaces. Several studies have examined the independent influence of each control strategy in mitigating transmission in isolation, yet controls are often implemented concomitantly within an indoor environment. To address the influence of physical distancing, universal masking, and ventilation on very fine respiratory droplets and aerosol particle exposure, a simulator that coughed and exhaled aerosols (the source) and a second breathing simulator (the recipient) were placed in an exposure chamber. When controlling for the other two mitigation strategies, universal masking with 3-ply cotton masks reduced exposure to 0.3-3 µm coughed and exhaled aerosol particles by >77% compared to unmasked tests, whereas physical distancing (0.9 or 1.8 m) significantly changed exposure to cough but not exhaled aerosols. The effectiveness of ventilation depended upon the respiratory activity, that is, coughing or breathing, as well as the duration of exposure time. Our results demonstrate that a layered mitigation strategy approach of administrative and engineering controls can reduce personal inhalation exposure to potentially infectious very fine respiratory droplets and aerosol particles within an indoor environment.


Subject(s)
Air Pollution, Indoor , COVID-19 , Masks , Physical Distancing , Ventilation , Air Pollution, Indoor/prevention & control , COVID-19/prevention & control , Humans , SARS-CoV-2
8.
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
9.
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
11.
PLoS One ; 16(6): e0253096, 2021.
Article in English | MEDLINE | ID: covidwho-1388924

ABSTRACT

BACKGROUND: In light of the role that airborne transmission plays in the spread of SARS-CoV-2, as well as the ongoing high global mortality from well-known airborne diseases such as tuberculosis and measles, there is an urgent need for practical ways of identifying congregate spaces where low ventilation levels contribute to high transmission risk. Poorly ventilated clinic spaces in particular may be high risk, due to the presence of both infectious and susceptible people. While relatively simple approaches to estimating ventilation rates exist, the approaches most frequently used in epidemiology cannot be used where occupancy varies, and so cannot be reliably applied in many of the types of spaces where they are most needed. METHODS: The aim of this study was to demonstrate the use of a non-steady state method to estimate the absolute ventilation rate, which can be applied in rooms where occupancy levels vary. We used data from a room in a primary healthcare clinic in a high TB and HIV prevalence setting, comprising indoor and outdoor carbon dioxide measurements and head counts (by age), taken over time. Two approaches were compared: approach 1 using a simple linear regression model and approach 2 using an ordinary differential equation model. RESULTS: The absolute ventilation rate, Q, using approach 1 was 2407 l/s [95% CI: 1632-3181] and Q from approach 2 was 2743 l/s [95% CI: 2139-4429]. CONCLUSIONS: We demonstrate two methods that can be used to estimate ventilation rate in busy congregate settings, such as clinic waiting rooms. Both approaches produced comparable results, however the simple linear regression method has the advantage of not requiring room volume measurements. These methods can be used to identify poorly-ventilated spaces, allowing measures to be taken to reduce the airborne transmission of pathogens such as Mycobacterium tuberculosis, measles, and SARS-CoV-2.


Subject(s)
Air Microbiology , Air Pollution, Indoor/prevention & control , COVID-19/prevention & control , COVID-19/transmission , Models, Biological , SARS-CoV-2 , Ventilation , COVID-19/epidemiology , Humans
12.
PLoS One ; 16(4): e0251049, 2021.
Article in English | MEDLINE | ID: covidwho-1388911

ABSTRACT

Respiratory infections, including SARS-CoV-2, are spread via inhalation or ingestion of airborne pathogens. Airborne transmission is difficult to control, particularly indoors. Manufacturers of high efficiency particulate air (HEPA) filters claim they remove almost all small particles including airborne bacteria and viruses. This study investigates whether modern portable, commercially available air filters reduce the incidence of respiratory infections and/or remove bacteria and viruses from indoor air. We systematically searched Medline, Embase and Cochrane for studies published between January 2000 and September 2020. Studies were eligible for inclusion if they included a portable, commercially available air filter in any indoor setting including care homes, schools or healthcare settings, investigating either associations with incidence of respiratory infections or removal and/or capture of aerosolised bacteria and viruses from the air within the filters. Dual data screening and extraction with narrative synthesis. No studies were found investigating the effects of air filters on the incidence of respiratory infections. Two studies investigated bacterial capture within filters and bacterial load in indoor air. One reported higher numbers of viable bacteria in the HEPA filter than in floor dust samples. The other reported HEPA filtration combined with ultraviolet light reduced bacterial load in the air by 41% (sampling time not reported). Neither paper investigated effects on viruses. There is an important absence of evidence regarding the effectiveness of a potentially cost-efficient intervention for indoor transmission of respiratory infections, including SARS-CoV-2. Two studies provide 'proof of principle' that air filters can capture airborne bacteria in an indoor setting. Randomised controlled trials are urgently needed to investigate effects of portable HEPA filters on incidence of respiratory infections.


Subject(s)
Air Filters , Air Pollution, Indoor/prevention & control , COVID-19/prevention & control , Respiratory Tract Infections/prevention & control , SARS-CoV-2/isolation & purification , Air Filters/microbiology , Air Filters/virology , Bacteria/isolation & purification , Communicable Disease Control/methods , Housing , Humans , Viruses/isolation & purification , Workplace
13.
Photochem Photobiol ; 97(3): 532-541, 2021 05.
Article in English | MEDLINE | ID: covidwho-1388390

ABSTRACT

During the current SARS-CoV-2 and tuberculosis global pandemics, public health and infection prevention and control professionals wrestle with cost-effective means to control airborne transmission. One technology recommended by Centers for Disease Control and Prevention and the World Health Organization for lowering indoor concentration of these and other microorganisms and viruses is upper-room ultraviolet 254 nm (UVC254 ) systems. Applying both a material balance as well as some nondimensional parameters developed by Rudnick and First, the impact of several critical parameters and their effect on the fraction of microorganisms surviving UVC254 exposure was evaluated. Vertical airspeed showed a large impact at velocities <0.05 m s-1 but a lesser effect at velocities >0.05 m s-1 . In addition, the efficacy of any upper-room UVC system is influenced greatly by the mean room fluence rate as opposed to a simple volume- or area-based dosing criteria. An alternative UVC254 dosing strategy was developed based on the fluence rate as a function of the UVC254 luminaire output (W) and the square root of the product of the room volume and the ceiling height.


Subject(s)
Air Microbiology , Disinfection/instrumentation , Disinfection/methods , Lighting , Ultraviolet Rays , Air Pollution, Indoor/prevention & control , Animals , COVID-19/prevention & control , Environment, Controlled , Infection Control/methods , SARS-CoV-2/radiation effects , Virus Inactivation/radiation effects
14.
Photochem Photobiol ; 97(3): 549-551, 2021 05.
Article in English | MEDLINE | ID: covidwho-1388389

ABSTRACT

Although the environmental control measure of ultraviolet germicidal irradiation (UVGI) for disinfection has not been widely used in the United States and some parts of the world in the past few decades, this technology has been well applied in Russia. UVGI technology has been particularly useful with regard to limiting TB transmission in medical facilities. There is good evidence that UV-C (180-280 nm) air disinfection can be a helpful intervention in reducing transmission of the SARS-CoV-2 virus.


Subject(s)
COVID-19/prevention & control , Disinfection/methods , Hospitals/standards , SARS-CoV-2/radiation effects , Ultraviolet Rays , Virus Inactivation/radiation effects , Air Microbiology , Air Pollution, Indoor/prevention & control , COVID-19/epidemiology , Disinfection/instrumentation , Humans , Infection Control , Russia
15.
Nat Commun ; 12(1): 5096, 2021 08 19.
Article in English | MEDLINE | ID: covidwho-1366815

ABSTRACT

Nearly all mass gathering events worldwide were banned at the beginning of the COVID-19 pandemic, as they were suspected of presenting a considerable risk for the transmission of SARS-CoV-2. We investigated the risk of transmitting SARS-CoV-2 by droplets and aerosols during an experimental indoor mass gathering event under three different hygiene practices, and used the data in a simulation study to estimate the resulting burden of disease under conditions of controlled epidemics. Our results show that the mean number of measured direct contacts per visitor was nine persons and this can be reduced substantially by appropriate hygiene practices. A comparison of two versions of ventilation with different air exchange rates and different airflows found that the system which performed worst allowed a ten-fold increase in the number of individuals exposed to infectious aerosols. The overall burden of infections resulting from indoor mass gatherings depends largely on the quality of the ventilation system and the hygiene practices. Presuming an effective ventilation system, indoor mass gathering events with suitable hygiene practices have a very small, if any, effect on epidemic spread.


Subject(s)
Air Pollution, Indoor/prevention & control , COVID-19/transmission , Hygiene/standards , SARS-CoV-2/pathogenicity , Ventilation/methods , Aerosols , COVID-19/diagnosis , COVID-19/virology , Computer Simulation , Disease Transmission, Infectious/prevention & control , Humans , SARS-CoV-2/genetics , SARS-CoV-2/isolation & purification
17.
MMWR Morb Mortal Wkly Rep ; 70(27): 972-976, 2021 Jul 09.
Article in English | MEDLINE | ID: covidwho-1302821

ABSTRACT

SARS-CoV-2, the virus that causes COVID-19, can be spread by exposure to droplets and aerosols of respiratory fluids that are released by infected persons when they cough, sing, talk, or exhale. To reduce indoor transmission of SARS-CoV-2 between persons, CDC recommends measures including physical distancing, universal masking (the use of face masks in public places by everyone who is not fully vaccinated), and increased room ventilation (1). Ventilation systems can be supplemented with portable high efficiency particulate air (HEPA) cleaners* to reduce the number of infectious particles in the air and provide enhanced protection from transmission between persons (2); two recent reports found that HEPA air cleaners in classrooms could reduce overall aerosol particle concentrations by ≥80% within 30 minutes (3,4). To investigate the effectiveness of portable HEPA air cleaners and universal masking at reducing exposure to exhaled aerosol particles, the investigation team used respiratory simulators to mimic a person with COVID-19 and other, uninfected persons in a conference room. The addition of two HEPA air cleaners that met the Environmental Protection Agency (EPA)-recommended clean air delivery rate (CADR) (5) reduced overall exposure to simulated exhaled aerosol particles by up to 65% without universal masking. Without the HEPA air cleaners, universal masking reduced the combined mean aerosol concentration by 72%. The combination of the two HEPA air cleaners and universal masking reduced overall exposure by up to 90%. The HEPA air cleaners were most effective when they were close to the aerosol source. These findings suggest that portable HEPA air cleaners can reduce exposure to SARS-CoV-2 aerosols in indoor environments, with greater reductions in exposure occurring when used in combination with universal masking.


Subject(s)
Air Conditioning/instrumentation , Air Filters , Air Pollution, Indoor/prevention & control , Masks , SARS-CoV-2 , Aerosols , Equipment Design , Humans , United States
18.
Ann Biomed Eng ; 49(9): 2554-2565, 2021 Sep.
Article in English | MEDLINE | ID: covidwho-1287444

ABSTRACT

Ultraviolet radiation as a germicide is widely used in the health field and even in domestic hygiene. Here, we propose an improvement in low-cost portable units of filtration for indoor air, which is based on ultraviolet radiation. In the current technology, to carry out an air filtration with a suspension of aerosols in which there is a likely concentration of pathogens, whether viral, bacterial or molds, the air is forced to pass as close as possible to the ionizing radiation source (near field). Since the optical mass is very small, the desired effect can be achieved in a considerably short time, deactivating the infective potential of these biological agents. The proposal of this work is the regulation of the flow or speed control of passage through these filters by passive elements instead of by electronic control systems. For this, two devices have been designed, simulated, and built, obtaining similar net pathogen inactivation rates under different flow rates. The passive flow control device has demonstrated higher performance in terms of flow rate and lower cost of production since they do not require electronics and are produced with fewer diodes. This passive device has also shown a lower projection of maintenance cost, lower energy consumption rate (higher efficiency), and longer projection of useful life.


Subject(s)
Air Filters , Air Pollution, Indoor/prevention & control , COVID-19/prevention & control , Microbial Viability/radiation effects , SARS-CoV-2/chemistry , Ultraviolet Rays , Aerosols , Humans
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