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Research review: Indoor air quality control techniques

Description: Techniques for controlling the concentration of radon, formaldehyde, and combustion products in the indoor air are reviewed. The most effective techniques, which are generally based on limiting or reducing indoor pollutant source strengths, can decrease indoor pollutant concentrations by a factor of 3 to 10. Unless the initial ventilation rate is unusually low, it is difficult to reduce indoor pollutant concentrations more than approximately 50% by increasing the ventilation rate of an entire building. However, the efficiency of indoor pollutant control by ventilation can be enhanced through the use of local exhaust ventilation near concentrated sources of pollutants, by minimizing short circuiting of air from supply to exhaust when pollutant sources are dispersed and, in some situations, by promoting a displacement flow of air and pollutants toward the exhaust. Active air cleaning is also examined briefly. Filtration and electrostatic air cleaning for removal of particles from the indoor air are the most practical and effective currently available techniques of air cleaning. 49 refs., 7 figs.
Date: October 1, 1986
Creator: Fisk, W.J.
Partner: UNT Libraries Government Documents Department

Improving the energy efficiency of residential clothes dryers

Description: An experimental study on energy efficient electrical domestic clothes dryers is presented. A literature survey was performed and four basic energy saving techniques were identified: (1) reduced air flow rate and heater input, (2) recirculation of a portion of the exhaust air back into the clothes dryer, (3) heat recovery, utilizing an air-to-air heat exchanger, and (4) 100% recirculation of air through the dryer and a heat pump to condense water out of the air. Reduced air flow rate and heater input leads to energy savings around 8%, while recirculation of exhaust air reduces the energy consumption by approximately 18%. Because of the low cost of these two measures, they should be pursued by the manufacturers. When utilizing an air-to-air heat exchanger for heat recovery, two modes are considered. The first is to preheat the inlet air with heat from the exhaust air, which results in 20 to 26% energy savings depending upon the location of the dryer in the house. The second more attractive mode is 100% recirculation of air and condensation of water from this air in the heat exchanger (using indoor air as a heat sink) and represents a 100% heat recovery but leads to a 1 to 6% increase in energy consumption. The development of a clothes dryer equipped with an air-to-air heat exchanger and a summer/winter switch (preheating mode in the summer and recirculation/condenstion mode in the winter) should be pursued by the manufacturers. Recirculation through a heat pump with condensation again gives a 100% heat recovery and can save up to 33% in energy consumption but yields long drying times due to limitations of the condenser temperature.
Date: July 1, 1983
Creator: Hekmat, D. & Fisk, W.J.
Partner: UNT Libraries Government Documents Department

The impacts of balanced and exhaust mechanical ventilation on indoor radon

Description: Models for estimating radon entry rates, indoor radon concentrations, and ventilation rates in houses with a basement or a vented crawl-space and ventilated by natural infiltration, mechanical exhaust ventilation, or balanced mechanical ventilation are described. Simulations are performed for a range of soil and housing characteristics using hourly weather data for the heating season in Spokane, WA. For a house with a basement, we show that any ventilation technique should be acceptable when the soil permeability is less than approximately 10/sup -12/m/sup 2/. However, exhaust ventilation leads to substantially higher indoor radon concentrations than infiltration or balanced ventilation with the same average air exchange rate when the soil permeability is 10/sup -10/m/sup 2/ or greater. For houses with a crawl-space, indoor radon concentrations are lowest with balanced ventilation, intermediate with exhaust ventilation, and highest with infiltration.
Date: February 1, 1987
Creator: Fisk, W.J. & Mowris, R.J.
Partner: UNT Libraries Government Documents Department

Indoor environmental quality and ventilation in U.S. office buildings: A view of current issues

Description: Much of the current focus on indoor environmental quality and ventilation in US office buildings is a response to sick building syndrome and occupant complaints about building-related health symptoms, poor indoor air quality, and thermal discomfort. The authors know that serious ``sick-building`` problems occur in a significant number of US office buildings and that a significant proportion of the occupants in many normal (non-sick) buildings report building-related health symptoms. Concerns about the health effects of environmental tobacco smoke have also focused attention on the indoor environment. The major responses of industry and governments, underway at the present time, are to restrict smoking in offices, to attempt to reduce the emissions of indoor pollutants, and to improve the operation of heating, ventilating and air conditioning (HVAC) systems. Better air filtration, improved HVAC commissioning and maintenance, and increased provisions for individual control of HVAC are some of the improvements in HVAC that are currently being, evaluated. In the future, the potential for improved productivity and reduced airborne transmission of infectious disease may become the major driving force for improved indoor environments.
Date: November 1, 1994
Creator: Fisk, W. J.
Partner: UNT Libraries Government Documents Department

IMPROVING THE ENERGY PERFORMANCE OF RESIDENTIAL CLOTHESDRYERS

Description: Experiments were conducted to evaluate four techniques to improve the energy efficiency of electrically-heated domestic clothes dryers. Reduced air flow rate and heater input led to energy savings around 8%, while recirculation of a portion of the exhaust air back into the clothes dryer reduced energy consumption by approximately 18%. These two measures are attractive because of their low cost. Two modes of using an air-to-air heat exchanger for heat recovery were considered. The first is to preheat the inlet air with heat from the exhaust air, which resulted in 20 to 26% energy savings. The second mode is 100% recirculation of air through the dryer and a heat exchanger and condensation of water from this air in the heat exchanger by using indoor air. as a heat sink. This resulted in 100% heat recovery (i.e., all heat was rejected to indoors) but the energy consumption of the dryer was increased by up to 6%. To maximize energy savings, a clothes dryer with a heat exchanger can be equipped to operate in the preheating mode in the summer and in the recirculation/condensation mode in the winter. The last measure investigated recirculation, through a heat pump (i.e., dehumidifier), also resulted in a 100% heat recovery and, in addition, up to a 33% reduction in dryer energy consumption, but this technique also yielded long drying times.
Date: February 1, 1984
Creator: Hekmat, D. & Fisk, W.J.
Partner: UNT Libraries Government Documents Department

Performance analysis of a windowed high temperature gas receiver using a suspension of ultrafine carbon particles as the absorber

Description: The results of an analytical study of the efficiency of single and double-windowed high temperature solar receivers suitable for use with small central tower or point focus dish collectors are summarized. A detailed window energy balance is used to predict the window temperature. The receiver energy losses, receiver efficiency, and associated thermodynamic cycle efficiency are calculated. The efficiencies for the base line design for single and double-windowed receivers are 93.8% and 95.4% respectively. A sensitivity analysis is used to determine the effects of varying the temperature, concentration ratio, and glass reflectivity.
Date: April 1, 1980
Creator: Fisk, W.J.; Wroblewski, D.E. Jr. & Hunt, A.J.
Partner: UNT Libraries Government Documents Department

Test results and methods: residential air-to-air heat exchangers for maintaining indoor air quality and saving money

Description: LBL has constructed a facility for testing various performance aspects of residential air-to-air heat exchangers. When used in conjunction with a mechanical ventilation system, a residential heat exchanger permits the adequate ventilation of a residence while recovering most of the energy normally lost during ventilation. By constructing or retrofitting a home so that it has low natural infiltration rates and by using a heat exchanger-ventilation system, a homeowner can save energy, reduce heating and cooling costs, and prevent the buildup of indoor-generated air contaminants. Results obtained on five different residential heat exchangers are presented. The performance criteria and the test facility are described. The performance parameters measured were heat exchanger effectiveness (a measure of heat transfer ability), airstream static pressure drop, and fan system performance. The performance of the five heat exchangers differed greatly. The ability to transfer heat ranged from 43% to 75% of the theoretical maximum. The resistance to air flow varied by a factor of two. One of the heat exchangers was highly susceptible to leakage between airstreams and one had an unstable performance. In the future, additional heat exchangers will be tested, a new test system will be used to measure cross-stream leakage, and the possibility and consequences of freeze-up within the heat exchangers will be investigated.
Date: February 1, 1981
Creator: Fisk, W.J.; Roseme, G.D. & Hollowell, C.D.
Partner: UNT Libraries Government Documents Department

Air exchange effectiveness in office buildings: Measurement techniques and results

Description: We define two air exchange effectiveness parameters which indicate the extent of short circuiting, mixing, or displacement air flow in an entire building, the air diffusion effectiveness which indicates the air flow pattern locally, and the normalized local age of air. After describing two tracer gas procedures for measuring these parameters, we discuss assumptions inherent in the data analysis that are often violated in large office buildings. To obtain valuable data, careful selection of buildings for measurements and assessments to determine if operating conditions are reasonably consistent with the assumptions are necessary. Multiple factors, in addition to the air flow pattern in the occupied space, can affect measurement results, consequently, the interpretation of measurements is not straightforward. We summarize the results of measurements in several office buildings and in a research laboratory. Almost all measurements indicate that the extent of both short circuiting and displacement flow is small. A moderate amount of short circuiting is evident from a few measurements in rooms with heated supply air. Ages of air and their reciprocals (local ventilation rates) often vary substantially between rooms, probably because of room-to-room variation in the rate of air supply. For future research, we suggest assessments of measurement accuracy, development of measurement approaches that may be practically applied for a broader range of buildings, and a greater focus on pollutant removal efficiencies.
Date: July 1, 1992
Creator: Fisk, W.J. & Faulkner, D.
Partner: UNT Libraries Government Documents Department

Air exchange effectiveness in office buildings: Measurement techniques and results

Description: We define two air exchange effectiveness parameters which indicate the extent of short circuiting, mixing, or displacement air flow in an entire building, the air diffusion effectiveness which indicates the air flow pattern locally, and the normalized local age of air. After describing two tracer gas procedures for measuring these parameters, we discuss assumptions inherent in the data analysis that are often violated in large office buildings. To obtain valuable data, careful selection of buildings for measurements and assessments to determine if operating conditions are reasonably consistent with the assumptions are necessary. Multiple factors, in addition to the air flow pattern in the occupied space, can affect measurement results, consequently, the interpretation of measurements is not straightforward. We summarize the results of measurements in several office buildings and in a research laboratory. Almost all measurements indicate that the extent of both short circuiting and displacement flow is small. A moderate amount of short circuiting is evident from a few measurements in rooms with heated supply air. Ages of air and their reciprocals (local ventilation rates) often vary substantially between rooms, probably because of room-to-room variation in the rate of air supply. For future research, we suggest assessments of measurement accuracy, development of measurement approaches that may be practically applied for a broader range of buildings, and a greater focus on pollutant removal efficiencies.
Date: July 1, 1992
Creator: Fisk, W. J. & Faulkner, D.
Partner: UNT Libraries Government Documents Department

Potential Nationwide Improvements in Productivity and Health from Better Indoor Environments

Description: Theoretical considerations and empirical data suggest that existing technologies and procedures can improve indoor environments in a manner that significantly increases productivity and health. Existing literature contains moderate to strong evidence that characteristics of buildings and indoor environments significantly influence rates of respiratory disease, allergy and asthma symptoms, sick building symptoms, and worker performance. While there is considerable uncertainty in our estimates of the magnitudes of productivity gains that may be obtained by providing better indoor environments, the projected gains are very large. For the U.S., we estimate potential annual savings and productivity gains of $6 to $19 billion from reduced respiratory disease, $1 to $4 billion from reduced allergies and asthma, $10 to $20 billion from reduced sick building syndrome symptoms, and $12 to $125 billion from direct improvements in worker performance that are unrelated to health. In two example calculations, the potential financial benefits of improving indoor environments exceed costs by a factor of 8 and 14. Productivity gains that are quantified and demonstrated could serve as a strong stimulus for energy efficiency measures that simultaneously improve the indoor environment.
Date: May 1, 1998
Creator: Fisk, W.J. & Rosenfeld, A.H.
Partner: UNT Libraries Government Documents Department

Saving energy and improving IAQ through application of advanced air cleaning technologies

Description: In the future, we may be able use air cleaning systems and reduce rates of ventilation (i.e., reduce rates of outdoor air supply) to save energy, with indoor air quality (IAQ) remaining constant or even improved. The opportunity is greatest for commercial buildings because they usually have a narrower range of indoor pollutant sources than homes. This article describes the types of air cleaning systems that will be needed in commercial buildings.
Date: March 1, 2011
Creator: Fisk, W.J; Destaillats, H. & Sidheswaran, M.A.
Partner: UNT Libraries Government Documents Department

Hygroscopic Fine Mode Particle Deposition on Electronic Circuitsand Resulting Degradation of Circuit Performance: An ExperimentalStudy

Description: A portion of electronic equipment failures is a consequenceof particle deposition on electronic circuits in normal indoorenvironments. Deposited hygroscopic particles reduce the electricalisolation (EI) between conductors. In laboratory experiments, weinvestigated the mechanisms, locations, and effects of particledeposition on electronic circuits with surface mounted chips (SMCs) andalso on small television sets. One set of electronics was exposed for 281h to an unusually high concentration of artificially-generated ammoniumsulfate particles while a second set (experimental controls) was exposedto normal indoor particles. The particle mass concentration in thehigh-exposure chamber was 500 times higher than normal. Televisionreliability was observed and the changes in EI between adjacent legs ofSMCs were measured. The experiments demonstrate the strong influence ofelectrostatic forces on the locations and rates of particle deposition.Although televisions did not fail after exposure to concentratedaerosols, the EI between adjacent legs of the SMCs was, in many cases,greatly diminished. Relative humidity had a very strong influence on themagnitude of EI. A qualitative explanation of the mechanisms of particledeposition and circuit degradation is proposed, including the role offibers. Finally, a potential method to reduce particle deposition onelectronic components is discussed.
Date: March 1, 1998
Creator: Litvak, Andres; Gadgil, A. & Fisk, W.J.
Partner: UNT Libraries Government Documents Department

Modeling radon entry into houses with basements: Model description and verification

Description: We model radon entry into basements using a previously developed three-dimensional steady-state finite difference model that has been modified in the following ways: first, cylindrical coordinates are used to take advantage of the symmetry of the problem in the horizontal plant; second, the configuration of the basement has been made more realistic by incorporating the concrete footer; third, a quadratic relationship between the pressure and flow in the L-shaped gap between slab, footer, and wall has been employed; fourth, the natural convection of the soil gas which follows from the heating of the basement in winter has been taken into account. The temperature field in the soil is determined from the equation of energy conservation, using the basement, surface, and deep-soil temperatures as boundary conditions. The pressure field is determined from Darcy's law and the equation of mass conservation (continuity), assuming that there is no flow across any boundary except the soil surface (atmospheric pressure) and the opening in the basement shell (fixed pressure). After the pressure and temperatures field have been obtained the velocity field is found from Darcy's law. Finally, the radon concentration field is found from the equation of mass-transport. The convective radon entry rate through the opening or openings is then calculated. In this paper we describe the modified model, compare the predicted radon entry rates with and without the consideration of thermal convection, and compare the predicted rates with determined from data from 7 houses in the Spokane River valley of Washington and Idaho. Although the predicted rate is much lower than the mean of the rates determined from measurements, errors in the measurement of soil permeability and variations in the permeability of the area immediately under the basement slab, which has a significant influence on the pressure field, can account for the range of ...
Date: January 1, 1991
Creator: Revzan, K.L.; Fisk, W.J. & Gadgil, A.J.
Partner: UNT Libraries Government Documents Department

Exclusion-list methodology for weatherization program in the Pacific Northwest

Description: The Bonneville Power Administration (BPA) weatherization program includes measures that have the effect of reducing the ventilation rate in the structures in question, thereby not only saving energy but also increasing the potential for increased concentrations of indoor-generated airborne pollutants. In order to avoid having a significant impact on the health of occupants, certain classes of homes were excluded on the basis of house characteristics that may serve as indicators of higher-than-average sources of indoor pollutants. The purpose of this document is to examine the list of excluded classes of homes and to delineate an approach for modifying that list in order to increase the number of houses for which infiltration-reducing measures are offered. The nature of the weatherization program, particularly with respect to infiltration reduction, what is known about the sources and concentrations of indoor pollutants, as well as their health effects are surveyed. Techniques for controlling levels of indoor pollutants, whether by source control or by ventilation and air cleaning, are reviewed. The main considerations relevant to changes in the exclusion list and for formulating the elements that ought to be available in conjunction with such alterations are identified. It is concluded that the two major exclusion classes, that for radon has the greatest potential for reformulation in the near future to permit offering of infiltration-reducing measures to a significantly larger number of homes than at present; a comparable basis for changing the wood-stove exclusion does not yet exist. It also appears feasible to offer infiltration-reducing measures, in some cases, even if an unvented combustion appliance or urea-formaldehyde (UF) foam insulation is present: for gas stoves, if provision of a ventilation hood is deemed adequate, and for UF foam insulation, if monitoring demonstrates low formaldehyde levels.
Date: May 1, 1982
Creator: Nero, A.V.; Turiel, I.; Fisk, W.J.; Cirman, J.R. & Traynor, C.W.
Partner: UNT Libraries Government Documents Department

Demonstration and Field Test of airjacket technology

Description: There are approximately 600,000 paint spray workers in the United States applying paints and coatings with some type of sprayer. Approximately 5% of these spray workers are in the South Coast Air Quality Management District (SCAQMD). These spray workers apply paints or other coatings to products such as bridges, houses, automobiles, wood and metal furniture, and other consumer and industrial products. The materials being sprayed include exterior and interior paints, lacquers, primers, shellacs, stains and varnishes. Our experimental findings indicate that the Airjacket does not significantly reduce the exposure of spray workers to paint fumes during HVLP spraying. The difference between ideal and actual spray paint procedures influence the mechanisms driving spray workers exposures to paint fumes and influence the viability of the Airjacket technology. In the ideal procedure, for which the Airjacket was conceived, the spray worker's exposure to paint fumes is due largely to the formation of a recirculating eddy between the spray worker and the object painted. The Airjacket ejects air to diminish and ventilate this eddy. In actual practice, exposures may result largely from directing paint upstream and from the bounce-back of the air/paint jet of the object being painted. The Airjacket, would not be expected to dramatically reduce exposures to paint fumes when the paint is not directed downstream or when the bounce-back of paint on the object creates a cloud of paint aerosols around the spray worker.
Date: June 1, 1998
Creator: Faulkner, D.; Fisk, W.J.; Gadgil, A.J. & Sullivan, D.P.
Partner: UNT Libraries Government Documents Department

Measurements and modeling of environmental tobacco smoke leakagefrom a simulated smoking room

Description: The purpose of this study is to quantify the effect ofvarious design and operating parameters on smoking room performance.Twenty-eight experiments were conducted in a simulated smoking room witha smoking machine and an automatic door opener. Measurements were made ofair flows, pressures, temperatures, two particle-phase ETS tracers, twogas-phase ETS tracers, and sulfur hexafluoride. Quantification of leakageflows, the effect of these leaks on smoking room performance andnon-smoker exposure, and the relative importance of each leakagemechanism are presented. The results indicate that the first priority foran effective smoking room is to depressurize it with respect to adjoiningnon-smoking areas. Another important ETS leakage mechanism is the pumpingaction of the smoking room door. Substituting a sliding door for astandard swing-type door reduced this source of ETS leakagesignificantly. Measured results correlated well with model predictions(R2 = 0.82-0.99).
Date: March 1, 2002
Creator: Wagner, J.; Sullivan, D.P.; Faulkner, D.; Gundel, L.A.; Fisk,W.J.; Alevantis, L.E. et al.
Partner: UNT Libraries Government Documents Department

Regional and National Estimates of the PotentialEnergy Use, Energy Cost, and CO{sub 2} Emissions Associated with Radon Mitigation by Sub-slab Depressurization

Description: Active sub-slab depressurization (SSD) systems are an effective means of reducing indoor radon concentrations in residential buildings. However, energy is required to operate the system fan and to heat or cool the resulting increased building ventilation. We present regional and national estimates of the energy requirements, operating expenses, and CO{sub 2} emissions associated with using SSD systems at saturation (i.e., in all U.S. homes with radon concentrations above the EPA remediation guideline and either basement or slab-on-grade construction). The primary source of uncertainty in these estimates is the impact of the SSD system on house ventilation rate. Overall, individual SSD system operating expenses are highest in the Northeast and Midwest at about $99 y{sup -1}, and lowest in the South and West at about $66 y{sup -1}. The fan consumes, on average, about 40% of the end-use energy used to operate the SSD system and accounts for about 60% of the annual expense. At saturation, regional impacts are largest in the Midwest because this area has a large number of mitigable houses and a relatively high heating load. We estimate that operating SSD systems in U.S. houses where it is both appropriate and possible (about 2.6 million houses), will annually consume 1.7 x 10{sup 4} (6.4 x 10{sup 3} to 3.9 x 10{sup 4}) TJ of end-use energy, cost $230 (130 to 400) million (at current energy prices), and generate 2.0 x 10{sup 9} (1.2 x 10{sup 9} to 3.5 x 10{sup 9}) kg of CO{sub 2}. Passive or energy efficient radon mitigation systems currently being developed offer opportunities to substantially reduce these impacts.
Date: March 1, 1996
Creator: Riley, W.J.; Fisk, W.J. & Gadgil, A.J.
Partner: UNT Libraries Government Documents Department

A study of the influence of a gravel subslab layer on radon entry rate using two basement structures

Description: In buildings with elevated radon concentrations, the dominant transport mechanism of radon is advective flow of soil gas into the building substructure. However, the building-soil system is often complex, making detailed studies of the radon source term difficult. In order to examine radon entry into buildings, the authors have constructed two room-size, precisely-fabricated basement structures at a site with relatively homogeneous, moderately permeable soil. The basements are identical except that one lies directly on native soil whereas the other lies on a high permeability aggregate layer. The soil pressure field and radon entry rate have been measured for different basement pressures and environmental conditions. The subslab gravel layer greatly enhances the advective entry of radon into the structure; when the structures are depressurized, the radon entry rate into the structure with the subslab gravel layer is more than a factor of 3 times the radon entry rate into the other structure for the same depressurization. The gravel subslab layer also spreads the pressure field around the structure, extending the field of influence of the structure and the region from which it draws radon.
Date: January 1, 1993
Creator: Robinson, A.L.; Sextro, R.G.; Fisk, W.J.; Garbesi, K.; Wooley, J. & Wollenberg, H.A.
Partner: UNT Libraries Government Documents Department

Radon and remedial action in Spokane River Valley residences: an interim report

Description: Fifty-six percent of 46 residences monitored in the Spokane River Valley in eastern Washington/northern Idaho have indoor radon concentrations above the National Council for Radiation Protection (NCRP) guidelines of 8 pCi/1. Indoor levels were over 20 pCi/1 in eight homes, and ranged up to 132 pCi/1 in one house. Radon concentrations declined by factors of 4 to 38 during summer months. Measurements of soil emanation rates, domestic water supply concentrations, and building material flux rates indicate that diffusion of radon does not significantly contribute to the high concentrations observed. Rather, radon entry is dominated by pressure-driven bulk soil gas transport, aggravated by the local subsurface soil composition and structure. A variety of radon control strategies are being evaluated in 14 of these homes. Sub-surface ventilation by depressurization and overpressurization, basement overpressurization, and crawlspace ventilation are capable of successfully reducing radon levels below 5 pCi/1 in these homes. House ventilation is appropriate in buildings with low-moderate concentrations, while sealing of cracks has been relatively ineffective.
Date: March 1, 1986
Creator: Turk, B.H.; Prill, R.J.; Fisk, W.J.; Grimsrud, D.T.; Moed, B.A. & Sextro, R.G.
Partner: UNT Libraries Government Documents Department

Control of respirable particles and radon progeny with portable air cleaners

Description: Eleven portable air cleaning devices have been evaluated for control of indoor concentrations of respirable particles and radon progeny. Following injection of cigarette smoke and radon in a room-size chamber, decay rates for particles and radon progeny concentrations were measured with and without air cleaner operation. Particle concentrations were obtained for total number concentration and for number concentration by particle size. In tests with no air cleaner the natural decay rate for cigarette smoke was observed to be 0.2 hr/sup -1/. Air cleaning rates for particles were found to be negligible for several small panel-filters, a residential ion-generator, and a pair of mixing fans. The electrostatic precipitators and extended surface filters tested had significant particle removal rates, and a HEPA-type filter was the most efficient air cleaner. The evaluation of radon progeny control produced similar results; the air cleaners which were effective in removing particles were also effective in removing radon progeny. At low particle concentrations plateout of the unattached radon progeny is an important removal mechanism. Based on data from these tests, the plateout rate for unattached progeny was found to be 15 hr/sup -1/. The unattached fraction and the overall removal rate due to deposition of attached and unattached nuclides have been estimated for each radon decay product as a function of particle concentration. While air cleaning can be effective in reducing total radon progeny, concentrations of unattached radon progeny can increase with increasing air cleaning. 39 references, 26 figures, 9 tables.
Date: February 1, 1984
Creator: Offermann, F.J.; Sextro, R.G.; Fisk, W.J.; Nazaroff, W.W.; Nero, A.V.; Revzan, K.L. et al.
Partner: UNT Libraries Government Documents Department

A study of the influence of a gravel subslab layer on radon entry rate using two basement structures

Description: In buildings with elevated radon concentrations, the dominant transport mechanism of radon is advective flow of soil gas into the building substructure. However, the building-soil system is often complex, making detailed studies of the radon source term difficult. In order to examine radon entry into buildings, the authors have constructed two room-size, precisely-fabricated basement structures at a site with relatively homogeneous, moderately permeable soil. The basements are identical except that one lies directly on native soil whereas the other lies on a high permeability aggregate layer. The soil pressure field and radon entry rate have been measured for different basement pressures and environmental conditions. The subslab gravel layer greatly enhances the advective entry of radon into the structure; when the structures are depressurized, the radon entry rate into the structure with the subslab gravel layer is more than a factor of 3 times the radon entry rate into the other structure for the same depressurization. The gravel subslab layer also spreads the pressure field around the structure, extending the field of influence of the structure and the region from which it draws radon.
Date: January 1, 1993
Creator: Robinson, A. L.; Sextro, R. G.; Fisk, W. J.; Garbesi, K.; Wooley, J. & Wollenberg, H. A.
Partner: UNT Libraries Government Documents Department

New Methods of Energy Efficient Radon Mitigation

Description: Two new radon mitigation techniques are introduced and their evaluation in a field study complemented by numerical model predictions is described. Based on numerical predictions, installation of a sub gravel membrane at the study site resulted in a factor of two reduction in indoor radon concentrations. Experimental data indicated that installation of 'short-circuit' pipes extending between the subslab gravel and outdoors, caused an additional factor of two decrease in the radon concentration. Consequently, the combination of these two passive radon mitigation features, called the membrane and short-circuit (MASC) technique, was associated with a factor of four reduction in indoor radon concentration. The energy-efficient active radon mitigation method, called efficient active subslab pressurization (EASP), required only 20% of the fan energy of conventional active subslab depressurization and reduced the indoor radon concentration by approximately a factor of 15, including the numerically-predicted impact of the sub-gravel membrane.
Date: May 1, 1994
Creator: Fisk, W.J.; Prill, R.J.; Wooley, J.; Bonnefous, Y.C.; Gadgil, A.J. & Riley, W.J.
Partner: UNT Libraries Government Documents Department

Evaluation of Ultra-Violet Photocatalytic Oxidation for Indoor AirApplications

Description: Acceptable indoor air quality in office buildings may be achieved with less energy by combining effective air cleaning systems for volatile organic compounds (VOCs) with particle filtration then by relying solely on ventilation. For such applications, ultraviolet photocatalytic oxidation (UVPCO) systems are being developed for VOC destruction. An experimental evaluation of a UVPCO system is reported. The evaluation was unique in that it employed complex mixtures of VOCs commonly found in office buildings at realistically low concentrations. VOC conversion efficiencies varied over a broad range, usually exceeded 20%, and were as high as {approx}80%. Conversion efficiency generally diminished with increased air flow rate. Significant amounts of formaldehyde and acetaldehyde were produced due to incomplete mineralization. The results indicate that formaldehyde and acetaldehyde production rates may need to be reduced before such UVPCO systems can be deployed safely in occupied buildings.
Date: February 1, 2006
Creator: Hodgson, A.T.; Sullivan, D.P. & Fisk, W.J.
Partner: UNT Libraries Government Documents Department