The Experts below are selected from a list of 2301 Experts worldwide ranked by ideXlab platform
Xudong Yang - One of the best experts on this subject based on the ideXlab platform.
-
a test based method for estimating the service life of adsorptive portable Air Cleaners in removing indoor formaldehyde
Building and Environment, 2019Co-Authors: Mengqiang Lv, Xudong YangAbstract:Abstract Portable Air Cleaners (PACs) with activated carbon filters are frequently used to remove gaseous contaminants. However, activated carbon has a limited adsorption capacity for small polar molecules, such as formaldehyde. Formaldehyde is a ubiquitous Air contaminant with hazardous effects to human health. Thus, characterizing carbon filter performance decay and being able to predict the service life of PACs is of high importance. This study proposes a testing method which enables the continuous measurement of the clean Air delivery rate (CADR). Vaporized formaldehyde was injected at a constant rate, i.e. 14 mg/h or 45 mg/h, into an Air-tight chamber where the PAC was operating. The CADR was calculated from the steady-state concentration in the chamber according to the mass-balance equation. An adsorptive PAC with a pleated composite filter of activated carbon and high efficiency particulate Air (HEPA) was tested until the CADR decreased to ca. 30% of its initial value. The functional relationship between the CADR and the cumulative adsorbed mass (CAM) of formaldehyde was established. Then, formaldehyde emission rates and ventilation rates in real Chinese residences were estimated by literature research. The obtained data were used in simulation to investigate PAC service life under a range of different situations. Test results showed that the CADR tended to decay exponentially with the CAM. According to the simulation, the CADR declined by 90% after a duration of 130–190 h under the most strenuous condition. However, PAC service life could be prolonged to more than 2000 h under realistic usage conditions.
-
a predictive model for the formaldehyde removal performance of sorption based portable Air Cleaners with pleated composite filter
Building and Environment, 2019Co-Authors: Mengqiang Lv, Xudong YangAbstract:Abstract Sorption-based portable Air Cleaners (PACs) are widely-used to remove gaseous contaminants. However, their capacity decline as a result of saturation cannot be well predicted through tests alone. Therefore, a predictive model to characterize the performance of a sorption-based PAC installed with a pleated composite filter is proposed in this paper. A salient merit of this proposed model is that once verified, it merely requires information regarding the adsorbent to simulate the assembled PAC. The model verification was conducted at three levels: 1) Dynamic adsorption test on the single-layer filter segment; 2) Contaminant removal test on the assembled PAC in the laboratory, which validated the extrapolation from the filter to the actual PAC unit; and 3) Field test in the research building. The third part estimated the robustness of the model in real situations. Formaldehyde was chosen as the target contaminant. Results show that the model can handle changes in significant factors including temperature, relative humidity, flow rate, and inlet concentration. It was successfully extrapolated to an assembled PAC and was able to capture the point of decline of the clean Air delivery rate (CADR) in the laboratory. Besides, the average relative errors between the tested and simulated results in the field test were under 20%, which is considered suitable for engineering applications.
-
performance of sorption based portable Air Cleaners in formaldehyde removal laboratory tests and field verification
Building and Environment, 2018Co-Authors: Mengqiang Lv, Xudong YangAbstract:Abstract Formaldehyde is one of the primary indoor Air contaminants that widely exists in construction materials and household consumable products. Acute exposure to formaldehyde causes irritation and dermal allergies, while chronic exposure can result in DNA and chromosomal damage. However, only a handful studies have evaluated formaldehyde removal capacities of portable Air Cleaners (PACs) both in the field and in the laboratory. The laboratory performance of PACs has not been statistically compared with their field performance. This study evaluated the initial formaldehyde removal capabilities of several relatively popular commercial sorption-based PACs in Chinese market by measuring their clean Air delivery rates (CADRs) in an 8 m3 environmental chamber. The modified ‘pull-down’ method was applied in this study, and the total operation time of the tested PACs was 1.5 h. The laboratory results showed wide variations in the CADRs (13.8 m3/h to 75.6 m3/h), which was in agreement with the CADRs reported in previous studies. A single-zone field test under natural ventilation was also conducted in a bedroom with an area of 25 m2 and a volume of 67.5 m3 using the best performing PAC. The results were statistically analyzed for any significant difference between the laboratory and field data. The difference between the laboratory and field performance of the tested PAC was insignificant at a confidence level of 95%.
William P Bahnfleth - One of the best experts on this subject based on the ideXlab platform.
-
estimating the effects of ambient conditions on the performance of uvgi Air Cleaners
Building and Environment, 2009Co-Authors: William P Bahnfleth, James D. FreihautAbstract:Abstract Ultraviolet germicidal irradiation (UVGI) uses UVC radiation produced by low pressure mercury vapor lamps to control biological Air contaminants. Ambient Air velocity and temperature have a strong effect on lamp output by influencing the lamp surface cold spot temperature. In-duct UVGI systems are particularly susceptible to ambient effects due to the range of velocity and temperature conditions they may experience. An analytical model of the effect of ambient conditions on lamp surface temperature was developed for three common lamp types in cross flow from a convective–radiative energy balance assuming constant surface temperature. For one lamp type, a single tube standard output lamp, UVC output and cold spot temperature data were obtained under typical in-duct operating conditions. Over an ambient temperature range of 10–32.2 °C and an Air velocity range of 0–3.25 m/s, measured cold spot temperature varied from 12.7 to 41.9 °C and measured lamp output varied by 68% of maximum. Surface temperatures predicted by the heat transfer model were 6–17 °C higher than corresponding measured cold spot temperatures, but were found to correlate well with cold spot temperature via a two-variable linear regression. When corrected using this relationship, the simple model predicted the cold spot temperature within 1 °C and lamp UVC output within ±5%. To illustrate its practical use, the calibrated lamp model was employed in a simulation of the control of a contaminant in a single-zone ventilation system by an in-duct UVGI device. In this example, failure to account for the impact of ambient condition effects resulted in under-prediction of average space concentration by approximately 20% relative to a constant output system operating at maximum UVC output.
-
Estimating the effects of ambient conditions on the performance of UVGI Air Cleaners
Building and Environment, 2009Co-Authors: Josephine Lau, William P Bahnfleth, James D. FreihautAbstract:Ultraviolet germicidal irradiation (UVGI) uses UVC radiation produced by low pressure mercury vapor lamps to control biological Air contaminants. Ambient Air velocity and temperature have a strong effect on lamp output by influencing the lamp surface cold spot temperature. In-duct UVGI systems are particularly susceptible to ambient effects due to the range of velocity and temperature conditions they may experience. An analytical model of the effect of ambient conditions on lamp surface temperature was developed for three common lamp types in cross flow from a convective-radiative energy balance assuming constant surface temperature. For one lamp type, a single tube standard output lamp, UVC output and cold spot temperature data were obtained under typical in-duct operating conditions. Over an ambient temperature range of 10-32.2 °C and an Air velocity range of 0-3.25 m/s, measured cold spot temperature varied from 12.7 to 41.9 °C and measured lamp output varied by 68% of maximum. Surface temperatures predicted by the heat transfer model were 6-17 °C higher than corresponding measured cold spot temperatures, but were found to correlate well with cold spot temperature via a two-variable linear regression. When corrected using this relationship, the simple model predicted the cold spot temperature within 1 °C and lamp UVC output within ±5%. To illustrate its practical use, the calibrated lamp model was employed in a simulation of the control of a contaminant in a single-zone ventilation system by an in-duct UVGI device. In this example, failure to account for the impact of ambient condition effects resulted in under-prediction of average space concentration by approximately 20% relative to a constant output system operating at maximum UVC output. © 2008 Elsevier Ltd. All rights reserved.
-
estimating the effects of ambient conditions and aging on the performance of uvgi Air Cleaners
6th International Conference on Indoor Air Quality Ventilation and Energy Conservation in Buildings: Sustainable Built Environment IAQVEC 2007, 2007Co-Authors: William P Bahnfleth, James D. FreihautAbstract:Ultraviolet germicidal irradiation (UVGI) uses UVC radiation produced by low pressure Hg vapor lamps to control biological Air contaminants. Lamp UV output depends on multiple factors, including accumulated operating time (age) and the thermal effects of ambient Air temperature and velocity. Additionally, the life of some lamp types depends on the frequency of on-off cycles. Models of lamp life as a function of cycling rate and lamp output as a function of age and ambient conditions are developed for three common standard output lamp types based on heat transfer theory and manufacturer’s lamp performance data. Example results are presented and a parametric study in the form of a 3 factorial experiment is used to identify significant factors affecting output and their interactions. A typical range of ambient conditions reduces lamp output by more than 30% of rated capacity and the inclusion of aging effects reduces capacity by as much as 70%. For given ambient conditions, performance varies substantially across lamp types due to their differing heat transfer characteristics. It is concluded that short term and long term variation of lamp output is highly significant and that modeling of such effects is necessary for accurate system design and analysis.
-
Indoor-Air quality: Issues and resolutions
HPAC Heating Piping AirConditioning Engineering, 2005Co-Authors: William P Bahnfleth, Wladyslaw Jan KowalskiAbstract:Some critical issues related to indoor-Air-quality (IAQ) are presented along with their salient solutions. Some contemporary indoor-Air-quality problems affecting the health and comfort of occupants and the progresses made towards laws and legislations related to IAQ are also presented. The development of 62.2 and 62.1 versions of the ANSI/ASHRAE Standard 62, Ventilation for Acceptable Indoor Air quality, which covers low-rise residential buildings in particular, and all buildings, respectively, are discussed. The developments made on technologies such as ultraviolet germicidal irradiation (UVGI), electrostatic filters, and gas-phase Air Cleaners, are also discussed.
Mengqiang Lv - One of the best experts on this subject based on the ideXlab platform.
-
a test based method for estimating the service life of adsorptive portable Air Cleaners in removing indoor formaldehyde
Building and Environment, 2019Co-Authors: Mengqiang Lv, Xudong YangAbstract:Abstract Portable Air Cleaners (PACs) with activated carbon filters are frequently used to remove gaseous contaminants. However, activated carbon has a limited adsorption capacity for small polar molecules, such as formaldehyde. Formaldehyde is a ubiquitous Air contaminant with hazardous effects to human health. Thus, characterizing carbon filter performance decay and being able to predict the service life of PACs is of high importance. This study proposes a testing method which enables the continuous measurement of the clean Air delivery rate (CADR). Vaporized formaldehyde was injected at a constant rate, i.e. 14 mg/h or 45 mg/h, into an Air-tight chamber where the PAC was operating. The CADR was calculated from the steady-state concentration in the chamber according to the mass-balance equation. An adsorptive PAC with a pleated composite filter of activated carbon and high efficiency particulate Air (HEPA) was tested until the CADR decreased to ca. 30% of its initial value. The functional relationship between the CADR and the cumulative adsorbed mass (CAM) of formaldehyde was established. Then, formaldehyde emission rates and ventilation rates in real Chinese residences were estimated by literature research. The obtained data were used in simulation to investigate PAC service life under a range of different situations. Test results showed that the CADR tended to decay exponentially with the CAM. According to the simulation, the CADR declined by 90% after a duration of 130–190 h under the most strenuous condition. However, PAC service life could be prolonged to more than 2000 h under realistic usage conditions.
-
a predictive model for the formaldehyde removal performance of sorption based portable Air Cleaners with pleated composite filter
Building and Environment, 2019Co-Authors: Mengqiang Lv, Xudong YangAbstract:Abstract Sorption-based portable Air Cleaners (PACs) are widely-used to remove gaseous contaminants. However, their capacity decline as a result of saturation cannot be well predicted through tests alone. Therefore, a predictive model to characterize the performance of a sorption-based PAC installed with a pleated composite filter is proposed in this paper. A salient merit of this proposed model is that once verified, it merely requires information regarding the adsorbent to simulate the assembled PAC. The model verification was conducted at three levels: 1) Dynamic adsorption test on the single-layer filter segment; 2) Contaminant removal test on the assembled PAC in the laboratory, which validated the extrapolation from the filter to the actual PAC unit; and 3) Field test in the research building. The third part estimated the robustness of the model in real situations. Formaldehyde was chosen as the target contaminant. Results show that the model can handle changes in significant factors including temperature, relative humidity, flow rate, and inlet concentration. It was successfully extrapolated to an assembled PAC and was able to capture the point of decline of the clean Air delivery rate (CADR) in the laboratory. Besides, the average relative errors between the tested and simulated results in the field test were under 20%, which is considered suitable for engineering applications.
-
performance of sorption based portable Air Cleaners in formaldehyde removal laboratory tests and field verification
Building and Environment, 2018Co-Authors: Mengqiang Lv, Xudong YangAbstract:Abstract Formaldehyde is one of the primary indoor Air contaminants that widely exists in construction materials and household consumable products. Acute exposure to formaldehyde causes irritation and dermal allergies, while chronic exposure can result in DNA and chromosomal damage. However, only a handful studies have evaluated formaldehyde removal capacities of portable Air Cleaners (PACs) both in the field and in the laboratory. The laboratory performance of PACs has not been statistically compared with their field performance. This study evaluated the initial formaldehyde removal capabilities of several relatively popular commercial sorption-based PACs in Chinese market by measuring their clean Air delivery rates (CADRs) in an 8 m3 environmental chamber. The modified ‘pull-down’ method was applied in this study, and the total operation time of the tested PACs was 1.5 h. The laboratory results showed wide variations in the CADRs (13.8 m3/h to 75.6 m3/h), which was in agreement with the CADRs reported in previous studies. A single-zone field test under natural ventilation was also conducted in a bedroom with an area of 25 m2 and a volume of 67.5 m3 using the best performing PAC. The results were statistically analyzed for any significant difference between the laboratory and field data. The difference between the laboratory and field performance of the tested PAC was insignificant at a confidence level of 95%.
Martin M Shafer - One of the best experts on this subject based on the ideXlab platform.
-
the impact of household Air Cleaners on the oxidative potential of pm2 5 and the role of metals and sources associated with indoor and outdoor exposure
Environmental Research, 2020Co-Authors: Collin Brehmer, Christina Norris, Michael H Bergin, Yinping Zhang, Junfeng Zhang, Karoline K Barkjohn, Marilyn Black, Zhen Li, Yanbo Teng, Martin M ShaferAbstract:Abstract The health effects associated with human exposure to Airborne fine particulate matter (PM2.5) have been linked to the ability of PM2.5 to facilitate the production of excess cellular reactive oxygen species (oxidative potential). Concern about the adverse human health impacts of PM2.5 has led to the increased use of indoor Air Cleaners to improve indoor Air quality, which can be an important environment for PM2.5 exposure. However, the degree to which the oxidative potential of indoor and personal PM2.5 can be influenced by an indoor Air cleaner remains unclear. In this study we enrolled 43 children with physician diagnosed asthma in suburban Shanghai, China and collected two pAired-sets of 48-h indoor, outdoor, and personal PM2.5 exposure samples. One set of samples was collected under “real filtration” during which a functioning Air cleaner was installed in the child's bedroom, and the other (“false filtration”) with an Air cleaner without internal filters. The PM2.5 samples were characterized by inductively coupled plasma mass spectroscopy for elements, and by an alveolar macrophage assay for oxidative potential. The sources of metals contributing to our samples were determined by the EPA Positive Matrix Factorization model. The oxidative potential was lower under real filtration compared to sham for indoor (median real/sham ratio: 0.260) and personal exposure (0.813) samples. Additionally, the sources of elements in PM2.5 that were reduced indoors and personal exposure samples by the Air cleaner (e.g. regional aerosol and roadway emissions) were found by univariate multiple regression models to be among those contributing to the oxidative potential of the samples. An IQR increase in the regional aerosol and roadway emissions sources was associated with a 107% (95% CI: 80.1–138%) and 38.1% (17.6–62.1%) increase in measured oxidative potential respectively. Our results indicate that indoor Air Cleaners can reduce the oxidative potential of indoor and personal exposure to PM2.5, which may lead to improved human health.
-
the impact of household Air Cleaners on the chemical composition and children s exposure to pm2 5 metal sources in suburban shanghai
Environmental Pollution, 2019Co-Authors: Collin Brehmer, Christina Norris, Martin M Shafer, Michael H Bergin, Yinping Zhang, Junfeng Zhang, Karoline K Barkjohn, Marilyn Black, Zhen Li, James J SchauerAbstract:Abstract Increased public awareness of the health impacts of atmospheric fine particulate matter (PM 2.5 ) has led to increased demand and deployment of indoor Air Cleaners. Yet, questions still remain about the effectiveness of indoor Air Cleaners on indoor PM 2.5 concentrations and personal exposure to potentially hazardous components of PM 2.5 . Metals in PM 2.5 have been associated with adverse health outcomes, so knowledge of their sources in urban indoor and outdoor areas and how exposures are influenced by indoor Air Cleaners would be beneficial for public health interventions. We collected 48-h indoor, outdoor, and personal PM 2.5 exposure samples for 43 homes with asthmatic children in suburban Shanghai, China during the spring months. Two sets of samples were collected for each household, one set with a functioning Air filter placed in the bedroom (“true filtration”) and the other with a non-functioning (“sham”) Air cleaner. PM 2.5 samples were analyzed for elements, elemental carbon, and organic carbon. The major sources of metals in PM 2.5 were determined by Positive Matrix Factorization (PMF) to be regional aerosol, resuspended dust, residual oil combustion, roadway emissions, alloy steel abrasion, and a lanthanum (La) and cerium (Ce) source. Under true filtration, the median indoor to outdoor percent removal across all elements increased from 31% to 78% and from 46% to 88% across all sources. Our findings suggest that indoor Air Cleaners are an effective strategy for reducing indoor concentrations of PM 2.5 metals from most sources, which could translate into improved health outcomes for some populations.
-
the influence of Air Cleaners on indoor particulate matter components and oxidative potential in residential households in beijing
Science of The Total Environment, 2018Co-Authors: Ying Zhan, Karoline K Johnson, Christina Norris, Martin M Shafer, Michael H Bergin, Yinping Zhang, Junfeng Zhang, James J SchauerAbstract:Abstract In many developing regions with poor Air quality, the use of Air filtration devices to clean indoor Air is growing rapidly. In this study, we collected indoor, outdoor and personal exposure filter-based samples of fine particulate matter (PM 2.5 ) with both properly operating, and sham Air Cleaners in six Beijing residences from July 24th to August 17th, 2016. Mass concentrations of PM 2.5 and several health relevant components of PM 2.5 including organic carbon, elemental carbon, sulfate, nitrate, ammonium, and 21 selected metals, were analyzed to evaluate the effectiveness of Air Cleaners. The effect of Air purification on PM 2.5 reactive oxygen species (ROS) activity, a metric of the oxidative potential of the aerosol, was also evaluated. The average indoor PM 2.5 concentration during true filtration was 8.47 μg/m 3 , compared to 49.0 μg/m 3 during sham filtration; thus, Air Cleaners can significantly reduce the indoor PM 2.5 concentration to well below WHO guideline levels and significantly lower all major components of PM 2.5 . However, the utility of Air Cleaners in reducing overall personal exposure to PM 2.5 and its components was marginal in this study: the average personal exposure PM 2.5 concentration was 67.8 and 51.1 μg/m 3 during true and sham filtration respectively, and it is likely due to the activity patterns of the subjects. Short-term exposure contributions from environments with high PM 2.5 concentrations, including exposure to traffic related emissions as well as uncharacterized indoor microenvironments, likely add substantially to the total PM 2.5 exposure burden. The toxicity assay indicates that the Air Cleaners can also significantly reduce ROS activity in the indoor environment; however, this decrease did not translate to a reduction in personal exposure. Elemental carbon, lead, and arsenic were well-correlated with the ROS activity, thus adding to the knowledge base of drivers for ROS activity.
James J Schauer - One of the best experts on this subject based on the ideXlab platform.
-
the impact of household Air Cleaners on the chemical composition and children s exposure to pm2 5 metal sources in suburban shanghai
Environmental Pollution, 2019Co-Authors: Collin Brehmer, Christina Norris, Martin M Shafer, Michael H Bergin, Yinping Zhang, Junfeng Zhang, Karoline K Barkjohn, Marilyn Black, Zhen Li, James J SchauerAbstract:Abstract Increased public awareness of the health impacts of atmospheric fine particulate matter (PM 2.5 ) has led to increased demand and deployment of indoor Air Cleaners. Yet, questions still remain about the effectiveness of indoor Air Cleaners on indoor PM 2.5 concentrations and personal exposure to potentially hazardous components of PM 2.5 . Metals in PM 2.5 have been associated with adverse health outcomes, so knowledge of their sources in urban indoor and outdoor areas and how exposures are influenced by indoor Air Cleaners would be beneficial for public health interventions. We collected 48-h indoor, outdoor, and personal PM 2.5 exposure samples for 43 homes with asthmatic children in suburban Shanghai, China during the spring months. Two sets of samples were collected for each household, one set with a functioning Air filter placed in the bedroom (“true filtration”) and the other with a non-functioning (“sham”) Air cleaner. PM 2.5 samples were analyzed for elements, elemental carbon, and organic carbon. The major sources of metals in PM 2.5 were determined by Positive Matrix Factorization (PMF) to be regional aerosol, resuspended dust, residual oil combustion, roadway emissions, alloy steel abrasion, and a lanthanum (La) and cerium (Ce) source. Under true filtration, the median indoor to outdoor percent removal across all elements increased from 31% to 78% and from 46% to 88% across all sources. Our findings suggest that indoor Air Cleaners are an effective strategy for reducing indoor concentrations of PM 2.5 metals from most sources, which could translate into improved health outcomes for some populations.
-
the influence of Air Cleaners on indoor particulate matter components and oxidative potential in residential households in beijing
Science of The Total Environment, 2018Co-Authors: Ying Zhan, Karoline K Johnson, Christina Norris, Martin M Shafer, Michael H Bergin, Yinping Zhang, Junfeng Zhang, James J SchauerAbstract:Abstract In many developing regions with poor Air quality, the use of Air filtration devices to clean indoor Air is growing rapidly. In this study, we collected indoor, outdoor and personal exposure filter-based samples of fine particulate matter (PM 2.5 ) with both properly operating, and sham Air Cleaners in six Beijing residences from July 24th to August 17th, 2016. Mass concentrations of PM 2.5 and several health relevant components of PM 2.5 including organic carbon, elemental carbon, sulfate, nitrate, ammonium, and 21 selected metals, were analyzed to evaluate the effectiveness of Air Cleaners. The effect of Air purification on PM 2.5 reactive oxygen species (ROS) activity, a metric of the oxidative potential of the aerosol, was also evaluated. The average indoor PM 2.5 concentration during true filtration was 8.47 μg/m 3 , compared to 49.0 μg/m 3 during sham filtration; thus, Air Cleaners can significantly reduce the indoor PM 2.5 concentration to well below WHO guideline levels and significantly lower all major components of PM 2.5 . However, the utility of Air Cleaners in reducing overall personal exposure to PM 2.5 and its components was marginal in this study: the average personal exposure PM 2.5 concentration was 67.8 and 51.1 μg/m 3 during true and sham filtration respectively, and it is likely due to the activity patterns of the subjects. Short-term exposure contributions from environments with high PM 2.5 concentrations, including exposure to traffic related emissions as well as uncharacterized indoor microenvironments, likely add substantially to the total PM 2.5 exposure burden. The toxicity assay indicates that the Air Cleaners can also significantly reduce ROS activity in the indoor environment; however, this decrease did not translate to a reduction in personal exposure. Elemental carbon, lead, and arsenic were well-correlated with the ROS activity, thus adding to the knowledge base of drivers for ROS activity.
