Indoor Air Contaminant Concentrations Research Articles

A preliminary assessment of the health impacts of indoor air contaminants determined using the DALY metric

Common metrics used for assessing air quality are based on guidelines and/or standards for regulating concentrations that should not be exceeded over a period. Exceeding those values would represent problematic situations. A lack of agreement on appropriate norms or standards deems this approach sub-optimal. Moreover, this approach does not relate a proportion of exceedance to specific health outcomes. A need to develop health-centered IAQ metrics that can quantify burden of disease in terms of epidemiological evidence of population morbidity and mortality supported by the best knowledge of health effects, is pressing. This work proposes an approach that harnesses the advantages of using disability adjusted life years (DALYs) as a valuable metric to quantify and rank the burden of household air pollution, as a global perspective. Two methods were used to compute DALYs, one mainly based on incidence data and another mainly based on effect factors (i.e. DALYs per unit-intake of contaminant of interest). The methods are based on the following parameters: risk estimates, baseline incidence rates, damage factors, indoor air contaminant concentrations, human toxicological & epidemiological effect factors, dose–response factors, cancer-related variables and breathing rates. Systematic searches and reviews of peer-reviewed literature (including systematic reviews and meta-analyses) were performed to find information on said input parameters. Meta-analysis was used to pooled and synthesise data from different studies. A Monte Carlo approach was used to model results in DALYs lost. Over 1000 articles were revised and overall ∼200 unique sources were used as sources of data. Ten contaminants were accounted for with specific risk estimates and damage factors data, for which human epidemiological effect factors were derived. Representative concentrations of 45 contaminants were calculated. Thirty-nine contaminants were accounted for human toxicological effect factors. Total pooled DALYs were estimated per 100,000 exposed population with corresponding uncertainty intervals. Estimated population-averaged annual cost, in DALYs lost, of chronic air contaminant inhalation in dwellings indicate that the contaminants with highest median DALY loss estimates are PM10 and PM2.5 (magnitudes of 103); PMcoarse, formaldehyde and NO2 could be found with magnitudes of 102; contaminants with magnitudes of 101 include radon and ozone, finally SO2 and acrolein would have magnitudes of 10°; mould-related bioaerosols could be of interest as well. The updated strategies allowed for the quantification of contaminants and health outcomes that were not accounted for in previous works. Computed DALYs have lower uncertainty intervals than those previously proposed. The updated methodology presented in this study may be used to assess cumulative health impacts of indoor air contaminants.

Comparison of Indoor Air Distribution in a Ceiling Cooling Room with Different Mechanical Ventilation Systems

This paper presents an experimental study concerning the influence of ventilation system type on indoor air distribution in a ceiling cooling (CC) room with mixing ventilation (MV), underfloor air distribution (UFAD) and stratum ventilation (SV) when the internal or external cooling load was increased from 41.5 W/m2to 69.5 W/m2. The distributions of indoor air temperature, air velocity and contaminant concentration were measured and evaluated by the vertical air temperature difference, turbulence intensity and contaminant removal effectiveness, respectively. The results show that when the ceiling surface temperature increased from 17.0°C to 26.0°C, the vertical air temperature differences, turbulence intensities and contaminant removal effectiveness were 0.2°C-0.4°C, 27%-34% and 0.53-0.85 with CC+MV, 0.2°C-1.2°C, 27%-43% and 0.68-1.25 with CC+UFAD and 0.3°C-0.9°C, 24%-40% and 0.5-0.83 with CC+SV. The CC+MV had the most uniform distributions of indoor air temperature and velocity, whereas the CC+UFAD had the most non-uniform distribution of indoor contaminant concentration.

Evaluation of fast fluid dynamics with different solving schemes on scalar transport equation for predicting indoor contaminant concentration

Predicting the transport of indoor pollution can assist designer to optimize ventilation mode of room. However, the high computational cost restricts the wide implementation of computational fluid dynamics (CFD) technique to predict indoor contaminant concentration. This study evaluated three potential numerical methods with scalar transport equation to resolve this dilemma which were combine fast fluid dynamics (FFD) and different solving schemes on scalar transport equation. To test the performance of three potential numerical methods, the conventional PISO algorithm was also employed to compare. A threedimensional ventilation case with experimental data of indoor CO2 concentration was adopted. The results show that the FFD with iterative scheme of scalar transport equation could predicting indoor CO2 concentration efficiently. The numerical method with semi-Lagrangian method and iterative scheme for predicting indoor air contaminant concentration could obtain satisfactory results at large time step size.

Influence of sensible cooling load on indoor air distribution in an office room with ceiling cooling and mixing ventilation

A mixing ventilation system integrated with a ceiling cooling system is a potential advanced heating, ventilation and air conditioning system for modern office buildings with a high sensible cooling load. This paper presents an evaluation of the effect of sensible cooling load on the indoor air distribution in a typical office room with mixing ventilation and ceiling cooling. The vertical distributions of indoor air temperature, air velocity and contaminant (CO2) concentration were evaluated by the vertical air temperature difference, turbulence intensity and contaminant removal effectiveness. The results showed that when the chilled ceiling surface temperature was increased from 15.0°C to 23.0°C and supply air temperature was decreased from 22.0°C to 19.0°C, the average vertical air temperature difference, turbulence intensity and contaminant removal effectiveness were 0.2°C–0.3°C, 27%–32% and 0.53–0.81 as both internal and external sensible cooling loads were 41.5 W/m2. Moreover, these evaluation indices varied slightly as the external sensible cooling load was increased from 41.5 W/m2 to 69.5 W/m2, whereas they varied greatly as the internal sensible cooling load was increased from 41.5 W/m2 to 69.5 W/m2. Hence, the external sensible cooling load could slightly affect the indoor air distribution, whereas the internal sensible cooling load could clearly affect the indoor air distribution in an office room with mixing ventilation and ceiling cooling.

Improved indoor environment through optimised ventilator and furniture positioning: A case of slum rehabilitation housing, Mumbai, India

This study optimized the ventilator and furniture location of a tenement unit in a low-income urban habitat to obtain maximum experiential indoor environmental quality (e-IEQ) over the breathing zone. Hypothetical interior layouts using a combination of the two design parameters of ventilator location and bed position were generated for optimizing the design layout. This layout could promote maximum indoor airflow and minimum indoor air temperature and contaminant concentration. In this study, an improved indoor environment is hypothesized to be attainable through improved natural ventilation and thermal performance in the occupied zones. A sequential methodology involving “parametric design modeling–computational simulation–multiobjective optimization–multicriteria decision making”-based framework was selected. Results exhibited that the currently designed tenement unit had a poor indoor environment, whereas the hypothesized iterated layout “optimized design layout, scenario 3 (ODL 3)” derived from the optimization and decision-making algorithm performed effectively in providing e-IEQ. An increase in experiential indoor air velocity by 0.2 m/s and a decrease in temperature by 2 °C were observed over the monitoring point in the ODL 3 considering the existing scenario. Therefore, this study can find a way toward the development of sustainable habitat design guidelines under upcoming slum redevelopment policies across the nation.

Impact of chilled ceiling on indoor air distribution in a room with mixing ventilation

A mixing ventilation (MV) system integrated with a chilled ceiling (CC) cooling system will be a potential advanced heating, ventilation and air conditioning (HVAC) system in the modern buildings. This paper presented an experimental study concerning the effect of CC on the indoor air distribution with MV when the internal and external sensible cooling loads changed. The vertical distributions of indoor air temperature, air velocity and contaminant (CO2) concentration were evaluated by the vertical air temperature difference, turbulence intensity and contaminant removal effectiveness, respectively. The results showed that when chilled ceiling surface temperature ranged from 17.0 °C to 26.0 °C, the average vertical air temperature difference, turbulence intensity and contaminant removal effectiveness were 0.2 °C–0.4 °C, 30%–36% and 0.6–0.84 when both internal and external sensible cooling loads were 41.5 W/m2. Moreover, the ranges of these evaluation indices varied slightly when the internal or external sensible cooling load increased from 41.5 W/m2 to 69.5 W/m2. Hence, the chilled ceiling had a slight impact on the indoor air distribution in a room with mixing ventilation. It is interestingly found that the small vertical air temperature difference coincided with the large turbulence intensity and contaminant removal effectiveness with different internal or external cooling loads.

Building science approaches for vapor intrusion studies.

Indoor air concentrations are susceptible to temporal and spatial variations and have long posed a challenge to characterize for vapor intrusion scientists, in part, because there was a lack of evidence to draw conclusions about the role that building and weather conditions played in altering vapor intrusion exposure risks. Importantly, a large body of evidence is available within the building science discipline that provides information to support vapor intrusion scientists in drawing connections about fate and transport processes that influence exposure risks. Modeling tools developed within the building sciences provide evidence of reported temporal and spatial variation of indoor air contaminant concentrations. In addition, these modeling tools can be useful by calculating building air exchange rates (AERs) using building specific features. Combining building science models with vapor intrusion models, new insight to facilitate decision-making by estimating indoor air concentrations and building ventilation conditions under various conditions can be gained. This review highlights existing building science research and summarizes the utility of building science models to improve vapor intrusion exposure risk assessments.

Factors affecting temporal variations in vapor intrusion-induced indoor air contaminant concentrations

Temporal variability in indoor air contaminant concentrations at vapor intrusion (VI) sites has been a concern for some time. We consider the source of the reported variability at VI sites located near Hill Air Force Base (AFB) in Utah, an EPA experimental house in Indiana, and Naval Air Station North Island in California. We focus in particular on how the indoor/outdoor pressure differences and air exchange rates affected indoor air contaminant concentrations at these sites. We investigate how these dynamics differ for a site that is characterized by a preferential pathway (like Hill AFB) and VI sites that are not influenced by such pathways, using three-dimensional fluid dynamics models and statistical analysis of the aforementioned sites. A preferential pathway can dramatically increase a VI site's sensitivity to build pressurization, provided there exist a medium allowing effective communication between a contaminant-delivering preferential pathway and the indoor air space, e.g. a permeable subslab space that may be provided by a gravel layer. Preferential pathways may also erroneously indicate the presence of indoor contaminant sources. At sites characterized by significant advective transport from the subslab to the indoor air space, much of the short-term variability in indoor air contaminant concentration can be explained by an impact of fluctuations in indoor/outdoor pressure differences. Meanwhile, air exchange rate variation drives most of the short-term variability at sites characterized by minor variations in advective transport.

Indoor air distribution in a room with underfloor air distribution and chilled ceiling: Effect of ceiling surface temperature and supply air velocity

An underfloor air distribution (UFAD) system integrated with a chilled ceiling (CC) cooling system may be a potential advanced heating, ventilation and air conditioning system in modern non-residential buildings with high sensible cooling loads. This article presents an experimental study concerning the effect of ceiling surface temperature and supply air velocity on the indoor air distribution in a room with UFAD as the internal and external sensible cooling loads change. The vertical distributions of indoor air temperature, air velocity and contaminant (CO2) concentration were evaluated by vertical air temperature difference (VATD), turbulence intensity (TI) and contaminant removal effectiveness (CRE), respectively. The results showed that the average VATD, TI and CRE levels were 0.5°C–1.0°C, 31%–41% and 0.85–1.06 when both internal and external sensible cooling loads were 41.5 W/m2. These evaluation indices varied clearly when the external sensible cooling load increased from 41.5 W/m2 to 69.5 W/m2, whereas they remained almost the same when the internal sensible cooling load increased from 41.5 W/m2 to 69.5 W/m2. The maximum TI coincided with the minimum CRE under the condition of a constant sensible cooling load. Moreover, an air diffusion performance index clearly reduced with an increase in the heat removal effectiveness. It is recommended that it is important to balance the indoor air quality and energy consumption in a room with UFAD + CC.

Examining the use of USEPA's Generic Attenuation Factor in determining groundwater screening levels for vapor intrusion.

A value of 0.001 is recommended by the United States Environmental Protection Agency (USEPA) for its groundwater-to-indoor air Generic Attenuation Factor (GAFG), used in assessing potential vapor intrusion (VI) impacts to indoor air, given measured groundwater concentrations of volatile chemicals of concern (e.g., chlorinated solvents). The GAFG can, in turn, be used for developing groundwater screening levels for VI given target indoor air quality screening levels. In this study, we examine the validity and applicability of the GAFG both for predicting indoor air impacts and for determining groundwater screening levels. This is done using both analysis of published data and screening model calculations. Among the 774 total paired groundwater-indoor air measurements in the USEPA's VI database (which were used by that agency to generate the GAFG) we found that there are 427 pairs for which a single groundwater measurement or interpolated value was applied to multiple buildings. In one case, up to 73 buildings were associated with a single interpolated groundwater value and in another case up to 15 buildings were associated with a single groundwater measurement (i.e, that the indoor air contaminant concentrations in all of the associated buildings were influenced by the concentration determined at a single point). In more than 70% of the cases (390 of 536 paired measurements in which horizontal building-monitoring well distance was recorded) the monitoring wells were located more than 30 meters (and some up to over 200 meters) from the associated buildings. In a few cases, the measurements in the database even improbably implied that soil gas contaminant concentrations increased, rather than decreased, in an upward direction from a contaminant source to a foundation slab. Such observations indicate problematic source characterization within the dataset used to generate the GAFG, and some indicate the possibility of a significant influence of a preferential contaminant pathway. While the inherent value of the USEPA database itself is not being questioned here, the above facts raise the very real possibility that the recommended groundwater attenuation factors are being influenced by variables or conditions that have not thus far been fully accounted for. In addition, the predicted groundwater attenuation factors often fall far beyond the upper limits of predictions from mathematical models of VI, ranging from screening models to detailed computational fluid dynamic models. All these models are based on the same fundamental conceptual site model, involving a vadose zone vapor transport pathway starting at an underlying uniform groundwater source and leading to the foundation of a building of concern. According to the analysis presented here, we believe that for scenarios for which such a "traditional" VI pathway is appropriate, 10-4 is a more appropriately conservative generic groundwater to indoor air attenuation factor than is the EPA-recommended 10-3. This is based both on the statistical analysis of USEPA's VI database, as well as the traditional mathematical models of VI. This result has been validated by comparison with results from some well documented field studies.

Numerical Study and Analysis on Combined Ventilation System in House Room

Indoor air quality is studied using numerical simulation method in house room based on the tracer gas. A comprehensive discussion of indoor air temperature and contaminant concentration distribution is given by the comparing analysis results. The results show that the cooperation of combined ventilation system and air conditioning system has preferable effect on decreasing indoor contamination concentration and improving indoor air quality.

Quantification of Vapor Intrusion Pathways: An Integration of Modeling and Site Characterization

Core Ideas A numerical model was developed based on comprehensive field site characterization. Modeling results and field measurements were comprehensively compared. Soil anisotropic property could significantly influence vapor intrusion pathways. Vapor intrusion was highly dependent on oxygen availability. Vapor intrusion of volatile organic compounds into buildings can be a significant source of human exposure to hazardous materials. Field assessment is essential to evaluate the vapor intrusion pathways, which can be challenging due to uncontrolled site environments. Mathematical modeling is expected to play significant roles to predict indoor air contaminant concentration and to provide guidance for vapor intrusion management. Efforts on field assessment and mathematical modeling, however, are not well integrated in current vapor intrusion management practice. This work seeks to quantify vapor intrusion pathways into a slab‐on‐ground building by integrating mathematical modeling with well‐controlled field measurements under three different pressure and ventilation site conditions. Mechanisms controlling vapor intrusion pathways were identified through systematic comparisons between modeled and measured indoor air concentration, contaminant and oxygen distribution profiles beneath the building, and diffusive and advective flux under different pressure and air ventilation conditions. Enhanced horizontal oxygen movement was found to be critical to evaluate vapor intrusion pathways, which can be attributed to the soil anisotropic properties in combination with vertical penetration of oxygen from slab. The dependency of oxygen concentration in the biodegradation modeling was found to be very important to describe the biodegradation of volatile hydrocarbons.

Impacts of changes of indoor air pressure and air exchange rate in vapor intrusion scenarios

There has, in recent years, been increasing interest in understanding the transport processes of relevance in vapor intrusion of volatile organic compounds (VOCs) into buildings on contaminated sites. These studies have included fate and transport modeling. Most such models have simplified the prediction of indoor air contaminant vapor concentrations by employing a steady state assumption, which often results in difficulties in reconciling these results with field measurements. This paper focuses on two major factors that may be subject to significant transients in vapor intrusion situations, including the indoor air pressure and the air exchange rate in the subject building. A three-dimensional finite element model was employed with consideration of daily and seasonal variations in these factors. From the results, the variations of indoor air pressure and air exchange rate are seen to contribute to significant variations in indoor air contaminant vapor concentrations. Depending upon the assumptions regarding the variations in these parameters, the results are only sometimes consistent with the reports of several orders of magnitude in indoor air concentration variations from field studies. The results point to the need to examine more carefully the interplay of these factors in order to quantitatively understand the variations in potential indoor air exposures.

Assessment of LEED Indoor Environmental Quality Parameters at a New Church Building In South-central Kentucky

ABSTRACT An indoor environmental quality assessment was conducted at a newly completed Catholic church building in South-central Kentucky as part of the United States Green Building Council's (USGBC's) Leadership in Energy and Environmental Design (LEED) certification requirements. From a business perspective, green building certification has become an important staple for demonstrating energy efficiency, environmental stewardship, and sustainability. The LEED certification process stipulates, among other things, that points be awarded for energy conservation as well as documentation that selected indoor air contaminant concentrations are below certain target levels. (It must be noted that any decision by a builder or architect aimed at obtaining the LEED credit point certification involves some financial commitment.) This article summarizes the results of a comprehensive indoor environmental quality assessment for four LEED chemical contaminants and selected parameters present in indoor air, with a view ...

A Review of Vapor Intrusion Models

A complete vapor intrusion (VI) model, describing vapor entry of volatile organic chemicals (VOCs) into buildings located on contaminated sites, generally consists of two main parts: one part describing vapor transport in the soil and the other describing its entry into the building. Modeling the soil vapor transport part involves either analytically or numerically solving the equations of vapor advection and diffusion in the subsurface. Contaminant biodegradation must often also be included in this simulation, and can increase the difficulty of obtaining a solution, especially when explicitly considering coupled oxygen transport and consumption. The models of contaminant building entry pathway are often coupled to calculations of indoor air contaminant concentration, and both are influenced by building construction and operational features. The description of entry pathway involves consideration of building foundation characteristics, while calculation of indoor air contaminant levels requires characterization of building enclosed space and air exchange within this. This review summarizes existing VI models, and discusses the limits of current screening tools commonly used in this field.

외기상태의 변화에 따른 실내 환경인자의 민감도 분석

The most important factors relating to the indoor air environment are temperature, airflow, humidity, and contaminant concentration. A sensitivity analysis of indoor environment factors was carried out to grasp influences along with changes of atmospheric conditions. An integrated multizone model was used to predict these sensitivities. This model was applied to an apartment with six zones. Airflow rates are influenced very seriously by changes of wind direct or wind velocity, but are influenced very slightly by changes of outdoor air temperature and are not influenced at all by changes of outdoor air humidity or contaminant concentration. Indoor air temperatures are influenced very directly by changes of outdoor air temperature, but are influenced very slightly by wind direction or wind velocity and are not influenced at all by changes of outdoor air humidity or contaminant concentration. Indoor air humidities are influenced very directly by changes of outdoor air humidity, but are not influenced at all by changes of outdoor air contaminant concentration and have little or no influence by changes of wind direction, wind velocity, or outdoor air temperature. Indoor air contaminant concentrations are influenced very seriously by changes of wind direct or wind velocity, but are influenced somewhat by changes of outdoor air contaminant concentration and are influenced very slightly by changes of outdoor air temperature and are not influenced at all by changes of outdoor air humidity.

Effects of inlet and exhaust locations and emitted gas density on indoor air contaminant concentrations

The steady-state distribution of contaminant concentrations in a workroom is a function of several factors, of which the types and relative position of air inlets and exhausts are some of the most important. Here several different inlet and exhaust locations and types (with or without diffuser) were investigated to determine the optimum inlet and exhaust positions. Room concentration patterns for a workroom were explored by computational fluid dynamics (CFD) simulations for various inlet locations, exhaust locations, contaminant gas densities, and dilution air flow rates. Average contaminant concentrations were calculated for the entire room, the breathing zone plane, and the near-source breathing zone (BZ). The computational results were validated with experimental results. For wall jet inlets and for lighter than air, the exhausts located near the ceiling resulted in lower concentrations than the corresponding exhausts near the floor. Also, the exhausts located on the same wall as the inlet were relatively better than that of the opposite side wall. The relative density of the contaminant was found to have some effects on the concentration distribution at low flow rates, whereas this effect was negligible at higher flow rates (8 ACH or higher). Exhaust location was not important for ceiling inlets as the room was well mixed. Although ceiling inlet type had almost no effect on average concentration, near-source concentrations were markedly less for the ceiling jet inlet than for the ceiling diffuser inlet.

Relationship between outdoor and indoor air quality in eight French schools

In the frame of the French national research program PRIMEQUAL (inter-ministry program for better air quality in urban environments), measurements of outdoor and indoor pollution have been carried out in eight schools in La Rochelle (France) and its suburbs. The buildings were naturally ventilated by opening the windows, or mechanically ventilated, and showed various air permeabilities. Ozone, nitrogen oxides (NO and NO(2)), and airborne particle (particle counts within 15 size intervals ranging from 0.3 to 15 mum) concentrations were continuously monitored indoors and outdoors for two 2-week periods. The indoor humidity, temperature, CO(2) concentration (an indicator of occupancy), window openings and building permeability were also measured. The temporal profiles of indoor and outdoor concentrations show ozone and nitrogen oxides behave differently: NO and NO(2) indoor/outdoor concentration ratios (I/O) were found to vary in a range from 0.5 to 1, and from 0.88 to 1, respectively, but no correlation with building permeability was observed. On the contrary, I/O ratios of ozone vary in a range from 0 to 0.45 and seem to be strongly influenced by the building air-tightness: the more airtight the building envelope, the lower the ratio. Occupancy, through re-suspension of previously deposited particles and possible particle generation, strongly influences the indoor concentration level of airborne particles. However, this influence decreases with particle size, reflecting the way deposition velocities vary as a function of size. The influence of particle size on deposition and penetration across the building envelope is also discussed by analyzing the I/O ratios measured when the buildings were unoccupied, by comparing the indoor concentrations measured when the buildings were occupied and when they were not (O/U ratios), and by referring to previously published studies focussing on this topic. Except one case, I/O were found to vary in the range from 0.03 to 1.79. All O/U are greater than one and increase up to 100 with particle size. Assessing children's total exposure requires the knowledge of outdoor and indoor air contaminant concentrations. The study presented here provides data on compared outdoor and indoor concentration levels in school buildings, as well as information on the parameters influencing the relationship between outdoor and indoor air quality. It may be used as a basis for estimating indoor concentrations from outdoor concentrations data, or as a first step in designing buildings sheltering children against atmospheric pollution.

An Evaluation of Vapor Intrusion Into Buildings through a Study of Field Data

A systematic examination of cases on file with the Massachusetts Department of Environmental Protection was undertaken to identify a universe of sites with volatile organic compound (VOC) contamination in groundwater in close proximity to buildings. Such locations were grouped according to site variables, such as contaminants of concern and concentrations in various media; soil type; depth to groundwater; distance to building; and building construction. Indoor air, soil gas, and/or groundwater field data collected from these sites was then assembled and used to: (1) evaluate available transport models which describe the intrusion of vapors into buildings and predict indoor air contaminant concentrations resulting from the volatilization of VOC s in the subsurface; (2) examine the validity of established regulatory criteria; (3) identify specific trends and field conditions which appear to most influence vapor phase contaminant migration and intrusion processes; and (4) evaluate the possibility of vapor migration being inhibited by a "freshwater lens".

Comparison of Different Subgrid-Scale Models of Large Eddy Simulation for Indoor Airflow Modeling

The Smagorinsky subgrid-scale model, a dynamic subgrid-scale model, and a stimulated subgrid-scale model have been used in a large eddy simulation (LES) program to compute airflow in a room. A fast Fourier transformation (FFT) method and a conventional iteration method were used in solving the Poisson equation. The predicted distributions of indoor air velocity, temperature, and contaminant concentrations show that the three subgrid-scale models can produce acceptable results for indoor environment design. The dynamic and stimulated models performed slightly better than the Smagorinsky model. The use of FFT can significantly reduce the computing time. LES is a tool of the next generation of indoor air distribution design.