Jensen Zhang | Syracuse University (original) (raw)

Papers by Jensen Zhang

Hygrothermal models for numerical simulation of heat and moisture transfer in building envelopes ... more Hygrothermal models for numerical simulation of heat and moisture transfer in building envelopes are already well developed and available to the scientific community. Building upon existing codes, the inclusion of air convection is an essential step towards realistic simulation of air permeable materials. Modeling the airflow effects on hygrothermal performance of vented roofs and lightweight wall assemblies is of particular practical relevance. Key element for an efficient numerical solution is the method of coupling of the balance equations for heat, air and moisture. Various numerical solution techniques exist for coupled non-linear systems of differential equations and have been successfully employed for solving two-dimensional coupled heat and moisture transport problems. However, finding an efficient solution scheme with acceptable accuracy for three-dimensional problems, including airflow effects, remains a challenge. The paper presents the governing equations and assumptions...

Energy and Buildings, 2020

Energy-saving building system integration with a smart and low-cost sensing/control network for s... more Energy-saving building system integration with a smart and low-cost sensing/control network for sustainable and healthy living environments: Demonstration case study, Energy & Buildings (2020), doi:

Healthy, Intelligent and Resilient Buildings and Urban Environments, 2018

In order to evaluate the impacts of volatile organic compounds (VOCs) emissions from building mat... more In order to evaluate the impacts of volatile organic compounds (VOCs) emissions from building materials on the indoor pollution load and indoor air quality beyond the standard chamber test conditions and test period, mechanistic emission source models have been developed in the past. However, very limited data are available for the required model parameters including the initial concentration (Cm0), in-material diffusion coefficient (Dm), partition coefficient (Kma), and convective mass transfer coefficient (km). In this study, a procedure is developed for estimating the model parameters by using VOC emission data from standard small chamber tests. Multivariate regression analysis on the experimental data are used to determine the parameters. The Least Square and Global search algorithm with multi-starting points are used to achieve a good agreement in the normalized VOC concentrations between the model prediction and experimental data. To verify the procedure and estimate its uncertainty, simulated chamber test data are first generated by superposition of different levels of "experimental uncertainties" on the theoretical curve of the analytical solution to a mechanistic model, and then the procedure is used to estimate the model parameters from these data and determine how well the estimates converged to the original parameter values used for the data generation. Results indicated that the mean value of the estimated model parameters Cm0 was within-0.04%+/-2.47% of the true values if the "experimental uncertainty" were within +/-10% (a typical uncertainty present in small-scale chamber testing). The procedure was further demonstrated by applying it to estimate the model parameters from real chamber test data. Wide applications of the procedure will result in a database of mechanistic source model parameters for assessing the impact of VOC emissions on indoor pollution load, and for evaluating the effectiveness of various IAQ design and control strategies.

Science and Technology for the Built Environment, 2020

The effects of moisture content, temperature and pollutant mixture on atmospheric corrosion of co... more The effects of moisture content, temperature and pollutant mixture on atmospheric corrosion of copper and silver were investigated by exposing test specimens to different environmental conditions, followed by surface characterization using the coulometric reduction, Scanning Electron Microscopy and Energy Dispersive Spectrometry (SEM/EDS). Printed circuit board test cards (PCBs) with bare copper were also used to investigate the effects of voltage bias on the PCBs on the corrosion rate. The test specimens were exposed to mixed flowing gases (MFG) environment with 8 different combinations of the following five pollutants at the fixed concentration levels: 60 ppb O3, 80 ppb NO2, 40 ppb SO2, 2 ppb Cl2 and 10 ppb H2S. Temperature and relative humidity were varied from a reference condition (210C and 50% RH which is within the current ASHRAE-recommended thermal envelope) to a higher value (28 C, 70% RH or 80% RH) to effect the moisture content of the test environment. The test results revealed the dominating effect of Cl2 on copper corrosion and that of H2S on silver corrosion. Increasing the moisture content at 21 C caused more severe corrosion for copper when Cl2 was present, but not for silver. When temperature was increased from 21 C to 28 C at 50% RH, it reduced the corrosion on copper, but not on silver. Voltage biased PCBs had a less effect on corrosion than PCBs without the bias. These results could be used for possible expansion of the ASHRAE-recommended thermal envelope for data centers when Cl2 and H2S are not present, and limit the thermal envelope when Cl2 or H2S are present.

Healthy, Intelligent and Resilient Buildings and Urban Environments, 2018

The purpose of this study is to investigate the main influential factors of the subway Particulat... more The purpose of this study is to investigate the main influential factors of the subway Particulate Matter (PM) pollutants under the airconditioning condition and ventilation condition, by an on-site field measurement in a subway station in Shanghai. It is found that the dust accumulation at fresh air shaft was the secondary dusting action under the influence of fresh air flow, leading to a higher concentration of the PM in the subway station than in the outdoor air even when the outdoor air quality was good. In addition, in the morning rush hour the PM 2.5 value near the platform screen door our is highest of the day.

Journal of hazardous materials, Jan 19, 2018

As the awareness of public health/safety becomes important and the desire to provide clean/safe i... more As the awareness of public health/safety becomes important and the desire to provide clean/safe indoor air in a sustainable way increases, air filtration technology has become essential at urban built facilities, which are challenged by significant outdoor air pollution due to dense population and heavy traffic. To provide comparable/objective data for designers and professionals of gas-phase filtration equipment in HVAC systems, it is important to understand the performance and characteristics of possible filter medium candidates within a reasonable testing period at low levels of target hazard concentration (typically, ∼0.05 ppm). The present study investigated the 2000-time scale-down evaluation evidence and its behind reasons between practical high-concentration tests (∼100 ppm NO) and actual low-concentration ones, and investigated potential dangers identified during the study in utilizing activated carbon (AC)-based virgin filter media in indoor applications due to unexpected ...

Journal of hazardous materials, Jan 5, 2017

Catalytic oxidation at ambient temperature has drawn wide attention as a new promising method of ... more Catalytic oxidation at ambient temperature has drawn wide attention as a new promising method of air cleaning, converting hazardous materials into non-hazardous ones. However, limited information is available regarding catalytic filter performance/characteristics under real operating conditions, especially on service efficiency and byproducts. Also, no practical scale-up method/evidence for filter performance evaluation is currently available to scale-up laboratory results to real application conditions. These limitations and knowledge gaps prevent building owners/designers from adopting this new promising technique in their commercial/industrial applications. The present study conducted experiments from small-scale to full-scale chamber tests which challenged a developed catalytic filter under realistic conditions. Formaldehyde was selected for approach demonstration due to its indoor ubiquitousness and criticality for human health even at low-levels. Results showed that the compet...

HVAC&R Research, 2014

ABSTRACT To guide the selection and design of air filter/cleaning devices for improving IAQ, it i... more ABSTRACT To guide the selection and design of air filter/cleaning devices for improving IAQ, it is important to be able to assess the performance and characteristics of filter media within a reasonable/practical testing period for the low concentrations conditions (~50 ppb) under which they are applied. The study objectives were to investigate whether filter media showing good performance at high concentrations per ASHRAE 145.1-2008 would also perform well at low concentrations typical indoors, and to explore whether and how existing models for filtration media beds can be applied to predict and extrapolate the experimental performance results obtained under high concentrations. Six filter media having different filtration property, pellet shape and size, and target compound were selected for this investigation. Experiments were performed at both high (~1 ppm/100 ppm) and low (~50 ppb) levels of O3/NO2 concentration for all media selected. Existing models were valuated for the feasibility of data extrapolation from high to low concentration conditions. The results showed that 1) the relative performance of filter media at high concentration was qualitatively indicative of that from the low concentration results; and 2) no existing models are suitable for any media having major catalytic removal characteristics for the cases studied, and an improved mechanistic model needs to be developed.

HVAC&R Research, 2014

To guide the selection of gas phase filtration media in the air cleaning devices, it is important... more To guide the selection of gas phase filtration media in the air cleaning devices, it is important to understand and estimate the media performance under usage concentrations. Filters for improving indoor air quality are typically subject to low volatile organic compounds (VOCs) concentration levels (e.g., ∼50 ppb), while the current standard tests per ASHRAE 145.1 (ANSI/ASHRAE 2008). are performed at relatively high challenge concentrations (∼1-100 ppm level). The primary objective of this study was to determine if media that perform well at the high concentration test condition would also perform well under the low concentration. The secondary objective was to investigate if and how existing models of filtration by media bed can be applied to extrapolate the results from the high concentration tests to the low concentration condition. Experiments and simulations were carried out at both high concentrations (100 ppm for toluene and 1 ppm for formaldehyde) and low concentrations (0.05 ppm for toluene and formaldehyde) for six selected filtration media. The results show that (1) the high concentration test data were able to differentiate the relative performance among the media at the low concentration properly, confirming the validity of using ASHRAE 145.1 (ANSI/ASHRAE 2008) for relative performance comparison; (2) significant initial breakthrough observed at high concentration tests of large pellet media was not present at the low concentration tests, indicating the dependency of the adsorption capability of the sorbent media on the concentration level as well as the possible "by-pass" effects (i.e., not all the VOC molecules in the air stream had the same chance to contact with the sorbent media); and (3) existing models need to be improved by incorporating the concentration dependency of the partition coefficient and the bypass effect in order to predict the breakthrough curve at low concentrations properly. Such an improved model was proposed, evaluated with the measured data, and was found to be promising for physical sorbent, but requires further development for chemical, catalytic sorbent and large pellet sorbent. The study provides previously unavailable experimental data and new insight into the behavior of the filtration media for volatile organic compounds as well as evidence in support of the application of ASHRAE Standard 145.1 (ANSI/ASHRAE 2008) for media performance evaluation.

The study objectives were to improve the understanding of the long-term variation of VOC emission... more The study objectives were to improve the understanding of the long-term variation of VOC emission chromatograms of building materials and to develop a method to account for this variation in the identification of individual sources of VOC emissions. This is of importance for the application of the source identification method since materials age over time in real indoor environments. The method is based on the mixed air sample measurements containing pollutants from multiple aged materials and the emission signatures of individual new materials determined by PTR-MS. Three emission decay source models were employed and evaluated for their ability to track the change of individual material emission signatures by PTR-MS over a nine-month period. Nine building material specimens were studied in a ventilated 50-L small-size chamber for their emissions individually for nine months, and also in combination later. Chamber exhaust air was sampled by PTR-MS to construct a temporal profile of emission signature unique to individual product type. The similar process was taken to measure mixture emissions from multiple materials, which is for applying and validating the developed method for source identification enhancement, considering the variation in long-term emission rates of individual VOCs. Results showed that the proposed approach could predict the emission signatures of individual building materials at a later time (9-month) with less than 6% difference variance, and hence indicated the potential of the source identification method for aged materials in real indoor environments.

Journal of hazardous materials, Jan 15, 2014

Botanical filtration has been proved to be effective for indoor gas pollutant removal. To underst... more Botanical filtration has been proved to be effective for indoor gas pollutant removal. To understand the roles of different transport, storage and removal mechanism by a dynamic botanical air filter, a series of experimental investigations were designed and conducted in this paper. Golden Pothos (Epipremnum aureum) plants was selected for test, and its original soil or activated/pebbles root bed was used in different test cases. It was found that flowing air through the root bed with microbes dynamically was essential to obtain meaningful formaldehyde removal efficiency. For static potted plant as normally place in rooms, the clean air delivery rate (CADR), which is often used to quantify the air cleaning ability of portable air cleaners, was only ∼ 5.1m(3)/h per m(2) bed, while when dynamically with air flow through the bed, the CADR increased to ∼ 233 m(3)/h per m(2) bed. The calculated CADR due to microbial activity is ∼ 108 m(3)/h per m(2) bed. Moisture in the root bed also play...

Energy and Buildings, 2014

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights

Building and Environment, 2011

A dynamic botanical air filtration system (DBAF) was developed for evaluating the short and long-... more A dynamic botanical air filtration system (DBAF) was developed for evaluating the short and long-term performance of botanical air cleaning technology under realistic indoor conditions. It was a fan-assisted with controlled airflow, activated-carbon/hydroculture based potted plant unit. The DBAF was first tested using a full-scale stainless chamber to evaluate its short-term performance. It was then integrated in the HVAC system of a new office space (96.8 m 2) to study the effects of moisture content in the root bed on the removal efficiency, and the long-term performance. The results indicated that 5% outdoor air plus botanical filtration lead to the similar indoor formaldehyde/toluene concentration level as 25% outdoor air without filtration, which means that the filtration system was equivalent to 20% outdoor air (476 m 3 /h). The DBAF was effective for removing both formaldehyde and toluene under 5e32% volumetric water content of the root bed. It also performed consistently well over the relatively long testing period of 300 days while running continuously. The reduction in outdoor ventilation rate while using the botanical filtration system to maintain acceptable air quality would lead to 10e15% energy saving for the cold climate (Syracuse, NY), based on simulation analysis using EnergyPlus. For winter condition, the filter was also found to increase the supply air RH by 20%, which would decrease the dryness of air. For summer condition, the increase of RH in summer would be within 15% of the RH condition when no botanical air filtration is present.

Atmospheric Environment, 2011

Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on ... more Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre-including this research content-immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

Healthy, Intelligent and Resilient Buildings and Urban Environments, 2018

Applying air cleaning devices is an effective approach to control targeted indoor gaseous polluta... more Applying air cleaning devices is an effective approach to control targeted indoor gaseous pollutants. It is important to understand the adsorption characteristics of filter media (e.g, activated carbon) at typical indoor application conditions as well as standard test conditions. Tests per ASHRAE Standard 145.1 for filter media performance evaluation can provide a relative comparison among different media. However, as the tests are conducted at elevated gas concentrations (1~100 ppm), they do not represent the media performance under lower concentrations typical of indoor applications (<0.1 ppm). Data are currently lacking for describing the correlation between the gas-phase filter media performance and the challenge concentration levels. In this study, single-pass adsorption tests were performed with smaller bed depth and pellet size than that specified in ASHRAE std 145.1 test protocol at four different concentration levels (50 ppb, 500 ppb, 5 ppm and 50 ppm). The data were used to determine the sorption isotherm and suggest a correlation between the partition coefficient and challenge concentration. Results revealed for the first time a linear correlation at log-log scale between the partition coefficient and the challenge concentration. Incorporation of this new correlation in a sorbent bed simulation model enabled the prediction of filter performance at low concentration based on the test data obtained from high concentration tests.

Building and Environment, 2012

The study objectives were to improve the understanding of the long-term variation of VOC emission... more The study objectives were to improve the understanding of the long-term variation of VOC emission chromatograms of building materials and to develop a method to account for this variation in the identification of individual sources of VOC emissions. This is of importance for the application of the source identification method since materials age over time in real indoor environments. The method is based on the mixed air sample measurements containing pollutants from multiple aged materials and the emission signatures of individual new materials determined by PTR-MS. Three emission decay source models were employed and evaluated for their ability to track the change of individual material emission signatures by PTR-MS over a nine-month period. Nine building material specimens were studied in a ventilated 50-L small-size chamber for their emissions individually for nine months, and also in combination later. Chamber exhaust air was sampled by PTR-MS to construct a temporal profile of emission signature unique to individual product type. The similar process was taken to measure mixture emissions from multiple materials, which is for applying and validating the developed method for source identification enhancement, considering the variation in long-term emission rates of individual VOCs. Results showed that the proposed approach could predict the emission signatures of individual building materials at a later time (9-month) with less than 6% difference variance, and hence indicated the potential of the source identification method for aged materials in real indoor environments.

Hygrothermal models for numerical simulation of heat and moisture transfer in building envelopes ... more Hygrothermal models for numerical simulation of heat and moisture transfer in building envelopes are already well developed and available to the scientific community. Building upon existing codes, the inclusion of air convection is an essential step towards realistic simulation of air permeable materials. Modeling the airflow effects on hygrothermal performance of vented roofs and lightweight wall assemblies is of particular practical relevance. Key element for an efficient numerical solution is the method of coupling of the balance equations for heat, air and moisture. Various numerical solution techniques exist for coupled non-linear systems of differential equations and have been successfully employed for solving two-dimensional coupled heat and moisture transport problems. However, finding an efficient solution scheme with acceptable accuracy for three-dimensional problems, including airflow effects, remains a challenge. The paper presents the governing equations and assumptions...

Energy and Buildings, 2020

Energy-saving building system integration with a smart and low-cost sensing/control network for s... more Energy-saving building system integration with a smart and low-cost sensing/control network for sustainable and healthy living environments: Demonstration case study, Energy & Buildings (2020), doi:

Healthy, Intelligent and Resilient Buildings and Urban Environments, 2018

In order to evaluate the impacts of volatile organic compounds (VOCs) emissions from building mat... more In order to evaluate the impacts of volatile organic compounds (VOCs) emissions from building materials on the indoor pollution load and indoor air quality beyond the standard chamber test conditions and test period, mechanistic emission source models have been developed in the past. However, very limited data are available for the required model parameters including the initial concentration (Cm0), in-material diffusion coefficient (Dm), partition coefficient (Kma), and convective mass transfer coefficient (km). In this study, a procedure is developed for estimating the model parameters by using VOC emission data from standard small chamber tests. Multivariate regression analysis on the experimental data are used to determine the parameters. The Least Square and Global search algorithm with multi-starting points are used to achieve a good agreement in the normalized VOC concentrations between the model prediction and experimental data. To verify the procedure and estimate its uncertainty, simulated chamber test data are first generated by superposition of different levels of "experimental uncertainties" on the theoretical curve of the analytical solution to a mechanistic model, and then the procedure is used to estimate the model parameters from these data and determine how well the estimates converged to the original parameter values used for the data generation. Results indicated that the mean value of the estimated model parameters Cm0 was within-0.04%+/-2.47% of the true values if the "experimental uncertainty" were within +/-10% (a typical uncertainty present in small-scale chamber testing). The procedure was further demonstrated by applying it to estimate the model parameters from real chamber test data. Wide applications of the procedure will result in a database of mechanistic source model parameters for assessing the impact of VOC emissions on indoor pollution load, and for evaluating the effectiveness of various IAQ design and control strategies.

Science and Technology for the Built Environment, 2020

The effects of moisture content, temperature and pollutant mixture on atmospheric corrosion of co... more The effects of moisture content, temperature and pollutant mixture on atmospheric corrosion of copper and silver were investigated by exposing test specimens to different environmental conditions, followed by surface characterization using the coulometric reduction, Scanning Electron Microscopy and Energy Dispersive Spectrometry (SEM/EDS). Printed circuit board test cards (PCBs) with bare copper were also used to investigate the effects of voltage bias on the PCBs on the corrosion rate. The test specimens were exposed to mixed flowing gases (MFG) environment with 8 different combinations of the following five pollutants at the fixed concentration levels: 60 ppb O3, 80 ppb NO2, 40 ppb SO2, 2 ppb Cl2 and 10 ppb H2S. Temperature and relative humidity were varied from a reference condition (210C and 50% RH which is within the current ASHRAE-recommended thermal envelope) to a higher value (28 C, 70% RH or 80% RH) to effect the moisture content of the test environment. The test results revealed the dominating effect of Cl2 on copper corrosion and that of H2S on silver corrosion. Increasing the moisture content at 21 C caused more severe corrosion for copper when Cl2 was present, but not for silver. When temperature was increased from 21 C to 28 C at 50% RH, it reduced the corrosion on copper, but not on silver. Voltage biased PCBs had a less effect on corrosion than PCBs without the bias. These results could be used for possible expansion of the ASHRAE-recommended thermal envelope for data centers when Cl2 and H2S are not present, and limit the thermal envelope when Cl2 or H2S are present.

Healthy, Intelligent and Resilient Buildings and Urban Environments, 2018

The purpose of this study is to investigate the main influential factors of the subway Particulat... more The purpose of this study is to investigate the main influential factors of the subway Particulate Matter (PM) pollutants under the airconditioning condition and ventilation condition, by an on-site field measurement in a subway station in Shanghai. It is found that the dust accumulation at fresh air shaft was the secondary dusting action under the influence of fresh air flow, leading to a higher concentration of the PM in the subway station than in the outdoor air even when the outdoor air quality was good. In addition, in the morning rush hour the PM 2.5 value near the platform screen door our is highest of the day.

Journal of hazardous materials, Jan 19, 2018

As the awareness of public health/safety becomes important and the desire to provide clean/safe i... more As the awareness of public health/safety becomes important and the desire to provide clean/safe indoor air in a sustainable way increases, air filtration technology has become essential at urban built facilities, which are challenged by significant outdoor air pollution due to dense population and heavy traffic. To provide comparable/objective data for designers and professionals of gas-phase filtration equipment in HVAC systems, it is important to understand the performance and characteristics of possible filter medium candidates within a reasonable testing period at low levels of target hazard concentration (typically, ∼0.05 ppm). The present study investigated the 2000-time scale-down evaluation evidence and its behind reasons between practical high-concentration tests (∼100 ppm NO) and actual low-concentration ones, and investigated potential dangers identified during the study in utilizing activated carbon (AC)-based virgin filter media in indoor applications due to unexpected ...

Journal of hazardous materials, Jan 5, 2017

Catalytic oxidation at ambient temperature has drawn wide attention as a new promising method of ... more Catalytic oxidation at ambient temperature has drawn wide attention as a new promising method of air cleaning, converting hazardous materials into non-hazardous ones. However, limited information is available regarding catalytic filter performance/characteristics under real operating conditions, especially on service efficiency and byproducts. Also, no practical scale-up method/evidence for filter performance evaluation is currently available to scale-up laboratory results to real application conditions. These limitations and knowledge gaps prevent building owners/designers from adopting this new promising technique in their commercial/industrial applications. The present study conducted experiments from small-scale to full-scale chamber tests which challenged a developed catalytic filter under realistic conditions. Formaldehyde was selected for approach demonstration due to its indoor ubiquitousness and criticality for human health even at low-levels. Results showed that the compet...

HVAC&R Research, 2014

ABSTRACT To guide the selection and design of air filter/cleaning devices for improving IAQ, it i... more ABSTRACT To guide the selection and design of air filter/cleaning devices for improving IAQ, it is important to be able to assess the performance and characteristics of filter media within a reasonable/practical testing period for the low concentrations conditions (~50 ppb) under which they are applied. The study objectives were to investigate whether filter media showing good performance at high concentrations per ASHRAE 145.1-2008 would also perform well at low concentrations typical indoors, and to explore whether and how existing models for filtration media beds can be applied to predict and extrapolate the experimental performance results obtained under high concentrations. Six filter media having different filtration property, pellet shape and size, and target compound were selected for this investigation. Experiments were performed at both high (~1 ppm/100 ppm) and low (~50 ppb) levels of O3/NO2 concentration for all media selected. Existing models were valuated for the feasibility of data extrapolation from high to low concentration conditions. The results showed that 1) the relative performance of filter media at high concentration was qualitatively indicative of that from the low concentration results; and 2) no existing models are suitable for any media having major catalytic removal characteristics for the cases studied, and an improved mechanistic model needs to be developed.

HVAC&R Research, 2014

To guide the selection of gas phase filtration media in the air cleaning devices, it is important... more To guide the selection of gas phase filtration media in the air cleaning devices, it is important to understand and estimate the media performance under usage concentrations. Filters for improving indoor air quality are typically subject to low volatile organic compounds (VOCs) concentration levels (e.g., ∼50 ppb), while the current standard tests per ASHRAE 145.1 (ANSI/ASHRAE 2008). are performed at relatively high challenge concentrations (∼1-100 ppm level). The primary objective of this study was to determine if media that perform well at the high concentration test condition would also perform well under the low concentration. The secondary objective was to investigate if and how existing models of filtration by media bed can be applied to extrapolate the results from the high concentration tests to the low concentration condition. Experiments and simulations were carried out at both high concentrations (100 ppm for toluene and 1 ppm for formaldehyde) and low concentrations (0.05 ppm for toluene and formaldehyde) for six selected filtration media. The results show that (1) the high concentration test data were able to differentiate the relative performance among the media at the low concentration properly, confirming the validity of using ASHRAE 145.1 (ANSI/ASHRAE 2008) for relative performance comparison; (2) significant initial breakthrough observed at high concentration tests of large pellet media was not present at the low concentration tests, indicating the dependency of the adsorption capability of the sorbent media on the concentration level as well as the possible "by-pass" effects (i.e., not all the VOC molecules in the air stream had the same chance to contact with the sorbent media); and (3) existing models need to be improved by incorporating the concentration dependency of the partition coefficient and the bypass effect in order to predict the breakthrough curve at low concentrations properly. Such an improved model was proposed, evaluated with the measured data, and was found to be promising for physical sorbent, but requires further development for chemical, catalytic sorbent and large pellet sorbent. The study provides previously unavailable experimental data and new insight into the behavior of the filtration media for volatile organic compounds as well as evidence in support of the application of ASHRAE Standard 145.1 (ANSI/ASHRAE 2008) for media performance evaluation.

The study objectives were to improve the understanding of the long-term variation of VOC emission... more The study objectives were to improve the understanding of the long-term variation of VOC emission chromatograms of building materials and to develop a method to account for this variation in the identification of individual sources of VOC emissions. This is of importance for the application of the source identification method since materials age over time in real indoor environments. The method is based on the mixed air sample measurements containing pollutants from multiple aged materials and the emission signatures of individual new materials determined by PTR-MS. Three emission decay source models were employed and evaluated for their ability to track the change of individual material emission signatures by PTR-MS over a nine-month period. Nine building material specimens were studied in a ventilated 50-L small-size chamber for their emissions individually for nine months, and also in combination later. Chamber exhaust air was sampled by PTR-MS to construct a temporal profile of emission signature unique to individual product type. The similar process was taken to measure mixture emissions from multiple materials, which is for applying and validating the developed method for source identification enhancement, considering the variation in long-term emission rates of individual VOCs. Results showed that the proposed approach could predict the emission signatures of individual building materials at a later time (9-month) with less than 6% difference variance, and hence indicated the potential of the source identification method for aged materials in real indoor environments.

Journal of hazardous materials, Jan 15, 2014

Botanical filtration has been proved to be effective for indoor gas pollutant removal. To underst... more Botanical filtration has been proved to be effective for indoor gas pollutant removal. To understand the roles of different transport, storage and removal mechanism by a dynamic botanical air filter, a series of experimental investigations were designed and conducted in this paper. Golden Pothos (Epipremnum aureum) plants was selected for test, and its original soil or activated/pebbles root bed was used in different test cases. It was found that flowing air through the root bed with microbes dynamically was essential to obtain meaningful formaldehyde removal efficiency. For static potted plant as normally place in rooms, the clean air delivery rate (CADR), which is often used to quantify the air cleaning ability of portable air cleaners, was only ∼ 5.1m(3)/h per m(2) bed, while when dynamically with air flow through the bed, the CADR increased to ∼ 233 m(3)/h per m(2) bed. The calculated CADR due to microbial activity is ∼ 108 m(3)/h per m(2) bed. Moisture in the root bed also play...

Energy and Buildings, 2014

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights

Building and Environment, 2011

A dynamic botanical air filtration system (DBAF) was developed for evaluating the short and long-... more A dynamic botanical air filtration system (DBAF) was developed for evaluating the short and long-term performance of botanical air cleaning technology under realistic indoor conditions. It was a fan-assisted with controlled airflow, activated-carbon/hydroculture based potted plant unit. The DBAF was first tested using a full-scale stainless chamber to evaluate its short-term performance. It was then integrated in the HVAC system of a new office space (96.8 m 2) to study the effects of moisture content in the root bed on the removal efficiency, and the long-term performance. The results indicated that 5% outdoor air plus botanical filtration lead to the similar indoor formaldehyde/toluene concentration level as 25% outdoor air without filtration, which means that the filtration system was equivalent to 20% outdoor air (476 m 3 /h). The DBAF was effective for removing both formaldehyde and toluene under 5e32% volumetric water content of the root bed. It also performed consistently well over the relatively long testing period of 300 days while running continuously. The reduction in outdoor ventilation rate while using the botanical filtration system to maintain acceptable air quality would lead to 10e15% energy saving for the cold climate (Syracuse, NY), based on simulation analysis using EnergyPlus. For winter condition, the filter was also found to increase the supply air RH by 20%, which would decrease the dryness of air. For summer condition, the increase of RH in summer would be within 15% of the RH condition when no botanical air filtration is present.

Atmospheric Environment, 2011

Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on ... more Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre-including this research content-immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

Healthy, Intelligent and Resilient Buildings and Urban Environments, 2018

Applying air cleaning devices is an effective approach to control targeted indoor gaseous polluta... more Applying air cleaning devices is an effective approach to control targeted indoor gaseous pollutants. It is important to understand the adsorption characteristics of filter media (e.g, activated carbon) at typical indoor application conditions as well as standard test conditions. Tests per ASHRAE Standard 145.1 for filter media performance evaluation can provide a relative comparison among different media. However, as the tests are conducted at elevated gas concentrations (1~100 ppm), they do not represent the media performance under lower concentrations typical of indoor applications (<0.1 ppm). Data are currently lacking for describing the correlation between the gas-phase filter media performance and the challenge concentration levels. In this study, single-pass adsorption tests were performed with smaller bed depth and pellet size than that specified in ASHRAE std 145.1 test protocol at four different concentration levels (50 ppb, 500 ppb, 5 ppm and 50 ppm). The data were used to determine the sorption isotherm and suggest a correlation between the partition coefficient and challenge concentration. Results revealed for the first time a linear correlation at log-log scale between the partition coefficient and the challenge concentration. Incorporation of this new correlation in a sorbent bed simulation model enabled the prediction of filter performance at low concentration based on the test data obtained from high concentration tests.

Building and Environment, 2012

The study objectives were to improve the understanding of the long-term variation of VOC emission... more The study objectives were to improve the understanding of the long-term variation of VOC emission chromatograms of building materials and to develop a method to account for this variation in the identification of individual sources of VOC emissions. This is of importance for the application of the source identification method since materials age over time in real indoor environments. The method is based on the mixed air sample measurements containing pollutants from multiple aged materials and the emission signatures of individual new materials determined by PTR-MS. Three emission decay source models were employed and evaluated for their ability to track the change of individual material emission signatures by PTR-MS over a nine-month period. Nine building material specimens were studied in a ventilated 50-L small-size chamber for their emissions individually for nine months, and also in combination later. Chamber exhaust air was sampled by PTR-MS to construct a temporal profile of emission signature unique to individual product type. The similar process was taken to measure mixture emissions from multiple materials, which is for applying and validating the developed method for source identification enhancement, considering the variation in long-term emission rates of individual VOCs. Results showed that the proposed approach could predict the emission signatures of individual building materials at a later time (9-month) with less than 6% difference variance, and hence indicated the potential of the source identification method for aged materials in real indoor environments.