This article was downloaded by: [Case Western Reserve University] On: 11 December 2014, At: 07:53 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of the Air & Waste Management Association Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/uawm18
Structural Dependence of Diurnal Fluctuations of Radon Progeny in Residential Buildings Ralph W. Sheets
a
a
Southwest Missouri State University , Springfield , Missouri , USA Published online: 07 Mar 2012.
To cite this article: Ralph W. Sheets (1992) Structural Dependence of Diurnal Fluctuations of Radon Progeny in Residential Buildings, Journal of the Air & Waste Management Association, 42:4, 457-459, DOI: 10.1080/10473289.1992.10467006 To link to this article: http://dx.doi.org/10.1080/10473289.1992.10467006
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
ISSN 1047-3289 J. Air Waste Manage. Assoc. 42:457-459
Structural Dependence of Diurnal Fluctuations of Radon Progeny in Residential Buildings Ralph W. Sheets
Downloaded by [Case Western Reserve University] at 07:53 11 December 2014
Southwest Missouri State University Springfield, Missouri
Movement of radon progeny inside houses is a complex process that depends both on atmospheric conditions and on building structure. The indoor working level (WL) monitored in four houses of differing structures shows regular diurnal fluctuations related to solar warming of the atmosphere. In the two houses with full basements, radon is removed by indoor/outdoor pressure-driven airflow, and basement WL varies inversely with outdoor temperature. In the two houses with half basements open to crawl spaces, radon is drawn into the basement faster than it is removed, so that basement WL varies directly with outside temperature. Average WL's in basements are about twice as high as first floor WL's and as much as 18 times as high as outdoor WL's. Each house shows an individual pattern of radon progeny movement throughout the building.
Outdoor radon (222Rn) concentrations near the ground fluctuate diurnally, with minimum concentrations occurring in the afternoon and evening hours, and maximum concentrations during the night and early morning.1""^ These diurnal patterns are attributed to variations in atmospheric stability, and it has been established that outdoor radon concentration is a periodic function of solar heating.3 Similarly, measurements of indoor radon have shown regular diurnal fluctuations inside houses.1-4 Spitz4 reported a diurnal fluctuation in the basement of a New Jersey house similar to the outdoor pattern with a morning maximum and an afternoon minimum. Harley et al.5 found different diurnal patterns in the basements of two houses: in one a positive correlation was found between basement radon concentration and indoor/outdoor temperature difference; in the other a negative correlation was observed. It thus appears that indoor radon patterns are structure-specific. Measurements of radon in hundreds of resi-
dences throughout the United States, funded by the U.S. Environmental Protection Agency and other government agencies, have investigated relationships between indoor radon and structural properties. Many of these studies are summarized in collections and handbooks.6 Models have also been developed to predict behavior of radon and its decay products indoors,7'8 and to relate lung cancer risk to indoor radon concentrations.9"11 In order to assess the health effects of indoor radon, it is important to know whether basement levels generally correlate with outdoor patterns and whether levels in living areas correlate with basement and crawl space levels. Since human health consequences of long term exposure are related, not to radon itself, but to its short-lived decay progeny ( 218 Po, 214pb> 214 Bij
and
214p o) 12
i t ig
eyen
more important to know how indoor concentrations of these nuclides vary. This study was designed to answer some of these questions.
Implications Buildup and removal of radon and its lung cancer-inducing progeny in houses depends on the structure of the building as well as on meteorological conditions. Concentrations of radon decay products in many houses fluctuate regularly over a 24-hour period as outside temperature changes. The patterns of increase and decrease are not identical in all houses, or even in different parts of the same house. This structure-dependent behavior is important in assessing health effects of indoor radon pollution.
Experimental
Radon daughter levels of four houses in the city of Springfield, Missouri, were monitored (Table I). The houses all lie near the central part of the city, but are located at least one mile apart. All houses were continuously occupied during the study. Measurements were made under a variety of conditions (weather, ventilation, heating/cooling), and no attempts were made to control any of these variables. Indoor levels of radon progeny measured in this way better reflect real-life conditions than do measurements made in studies which attempt to control these variables. Continuous monitoring was carried out over periods of 3 to 6 days in several different months (November; March-June). Parameters measured include: outdoor temperature, pressure, and relative humidity; indoor temperature, pressure, and relative humidity; outdoor working level (WL) (a measure of total radon progeny concentration); and indoor WL. Working levels were continuously monitored by an Eberline monitoring system with alpha activity averaged over one-hour periods. The system consisted of two WLM-1A working level monitors and a WLR-1A readout unit. Air flow rates were calibrated with a flowmeter and the solid state alpha counters were calibrated with a 0.00493 microCurie (182 Bq) NBS-traceable 230 Th source. Usually two sites at each structure were monitored simultaneously (e.g., indoors/outdoors, or basement/first floor). Temperature, atmospheric pressure, and relative humidity were monitored by Cole Parmer recording instruments at the same locations as the working level monitors. All measurements were made at ground or floor level. Results and Discussion
For all parameters (WL, temperature, atmospheric pressure and relaCopyright 1992—Air & Waste Management Association
April 1992
Volume 42, No. 4
457
Downloaded by [Case Western Reserve University] at 07:53 11 December 2014
Table I. Description of houses monitored in Springfield, Missouri. House
Description
A B C D
Brick—One Story—Full Basement (Finished) Brick—One Story—Full Basement (1/2 Finished) Brick—One Story—1/2 Basement, 1/2 Crawl Space Frame—Two Story—1/2 Basement, 1/2 Crawl Space
30+ Years 30+ Years 30+ Years 30+ Years
tive humidity) regular diurnal patterns emerged when data collected for several days were averaged over a 24hour period. To a first approximation the diurnal fluctuations in pressure and relative humidity in the houses investigated were found to be inversely proportional to the diurnal fluctuations in temperature. Thus these parameters added little information beyond that provided by temperature measurements alone. Since average indoor temperatures were relatively constant, the relationship between WL
and outdoor temperature was examined. For comparison, outdoor WL and temperature values at House A collected for three consecutive days in June 1988, and averaged over a 24hour period (local standard time) are given in Figure 1. The inverse relationship between the two variables is clearly evident. Figure 2 shows indoor diurnal WL fluctuation together with the outdoor average temperature during a 9-day period in March and April 1988. The indoor WL patterns are
28
_
LOCAL STANDARD TIME (HR)
Figure 1. Diurnal fluctuation of outdoor working level (WL) and outdoor temperature at house A (three-day mean). WLB 140
TEMP
-
120
L 1OO
80
WLF
60
40
/
A
on
LOCAL STANDARD TIME (HR)
Figure 2. Diurnal fluctuation in working level (WLB), working level on first floor (WLF), and outdoor temperature at house A (nine-day mean).
458
seen to be similar to the outdoor patterns and are due to the same cause: solar heating of the atmosphere. The resulting decreased density of the outdoor air causes it to rise, diluting the outdoor WL and causing a decrease in outdoor pressure relative to indoor pressure. Airflow from the higher pressure indoor environment to the outside carries radon and its decay products out of the building, decreasing the indoor WL. Similar patterns are observed both in the basement and on the first floor. Anomalous behavior was observed during several early morning periods when outside temperature dropped below about 5°C. During these times, indoor WL's appeared to be directly related to outdoor temperature (Figure 2). This is due to convective flow of air out of the warm house, which causes a decrease in indoor WL. House A is a one-story brick building with a full, finished (occupied) basement. Simultaneous measurements were made in the basement and in the living room directly above during a 6-day period in March 1988. Measurements were made in the basement and in a bedroom above for three different 3-day periods in April 1988. Diurnal plots of all data were similar to Figure 2. In general, WL's in various parts of the house are directly proportional to each other and inversely related to the outdoor temperature. Minimum WL's occur around 4 pm (CST), corresponding to maximum outdoor temperature. Maximum WL's occur during the night. Correlation analysis shows R2 values of about 0.70.9. The higher correlations are obtained by offsetting the dependent variable to correct for the lag time inherent in measurement of the decay products of radon. The ratio of WL(Outdoor): WL(Bedroom):WL(Living Room):WL(Basement) was approximately 1:3:4:8. House B has a structure much like House A. It is a brick, one-story building with a full basement. Only half the basement is finished and occupied, however. The other half is enclosed in unfinished concrete. Measurements of WL and temperature made during May-June 1988 yielded diurnal plots very similar to Figure 2. Working levels in both parts of the basement and in a bedroom directly above the unfinished basement were directly proportional to each other and inversely related to outdoor temperature (R2 values of 0.7-0.8). The ratio of WL (Outdoor):WL(Bedroom):WL(Finished Basement) :WL(Unfinished Basement) was about 1:5:5:10. House C is also a one-story brick building, but its basement is different from Houses A and B. In House C, one-half of the house lies over an enclosed unfinished concrete basement, and the other half over an enJ. Air Waste Manage. Assoc.
Downloaded by [Case Western Reserve University] at 07:53 11 December 2014
closed, dirt-filled crawl space. There is a large opening (4 x 12 feet) which allows free interchange of air between the basement and crawl space. In House C, WL and temperature were monitored for a total of 44 days in November 1986 and March-May 1987. All diurnal plots are similar to Figure 3. The WL in a first floor bedroom above the basement shows the diurnal pattern found in Houses A and B. Minimum WL's are reached around 6-8 pm and maximum levels in the morning hours. Figure 3 shows that, unlike the other houses, diurnal WL fluctuation in the basement of House C varies directly with outdoor temperature and inversely with first floor WL. WL in the crawl space followed the basement pattern, being directly proportional to both outdoor temperature and basement WL. The average ratio of WL(Outdoor):WL(First Floor): WL(Basement):WL(Crawl Space) was about 1:6:12:18. The diurnal pattern observed in House C can be explained as follows: the outdoor/indoor pressure differential caused by afternoon solar heating results in convective flow of air out of the house. In the upper part of the house, which is shielded from the crawl space, radon and its progeny are drawn out of the house, reducing the WL. The same convective effect, however, draws air and radon gas from the soil in the crawl space and into the basement. The net effect is that radon and decay products enter the basement faster than they are removed. Table II. Dependence of indoor working level (WL) on outdoor temperature. Crawl Space
House A B C D
No Crawl Space No Crawl Space Direct Direct
Basement
First Floor
Inverse
Inverse
Inverse Direct Direct
Inverse Inverse Direct
20 LOCAL STANDARD TIME (HR)
Figure 3. Diurnal fluctuation of working level in basement (WLB), on first floor (WLF), and outdoor temperature at house C (six-day mean).
living room (above the basement) show weaker diurnal variations that appear to be positively correlated with outdoor temperature, and with the basement and crawl space WL's. Measurement of WL in two bedrooms of the second floor show no diurnal effect. In these rooms there is a rather constant, low level of radon progeny only slightly higher than the average outdoor level. The average ratio of WL(Outdoor): WL(Second Floor): WL(Living Room): WL(Dining Room):WL(Basement):WL(Crawl Space) is about 1:1:2:3:6:12. Table II summarizes diurnal WL patterns of the four houses included in this study. The results indicate that outdoor temperature (or indoor/outdoor temperature difference) has a large effect on indoor radon progeny concentrations. The effects do depend on specific structural variations, however, and these factors need to be kept in mind in designing laboratory models in applying results of model studies to real-life situations. Acknowledgment
A similar pattern is seen in House D. This house is a two-story frame house quite unlike the other three in construction. It is similar to House C in that it has a one-half unfinished basement which is open to an enclosed crawl space through two 3 x 3 ft holes. Monitoring of this house in April-June 1986 indicated that its WL pattern resembles House C more than Houses A and B. The crawl space and basement show a strong diurnal effect with maximum WL occurring in midafternoon and minimum values around midnight. In this house, maxima and minima in the basement lag 1-2 hours behind corresponding maxima and minima in the crawl space. The dining room (above the crawl space) and the April 1992
Volume 42, No. 4
This work was sponsored in part by the Air Force Office of Scientific Research, Boiling AFB, DC(S-760-OMG032). References 1. 222 Gesell, T. F. "Background atmospheric Rn concentration outdoors and indoors: a review," Health Phys. 45: 289 (1983). 2. U.S. Dept. of Energy, Indoor Air Quality Environmental Information Handbook: Radon, National Technical Information Service, Springfield, Virginia, 1986, pp. 2-24. 3. Garzon, L.; Juanco, J. M.; Perez, J. M.; Fernandez, J. M.; Arganza, B. "The universal Rn wave: an approach," Health Phys. 51:185 (1986). 4. Spitz, H. B.; Wrenn, M. E.; Cohen, N. "Diurnal Variation of Radon Measured
Indoors and Outdoors in Grand Junction, Colorado, and Teaneck, New Jersey, and the Influence that Ventilation has on Buildup of Radon Indoors," in Natural Radiation Environment III, U.S. Dept. of Energy, Special Symposium Series 51, CONF 780422,1980, p. 1308. 5. Harley, N. H.; Terilli, T. B.; Khademi, B. "Indoor radon related to indoor outdoor temperature difference," abstract in Thirty-Third Annual Meeting of the Health Physics Society, Health Phys. 54: (Supplement 1), Abstract WAM-F4 (1988). 6. Nagda, N. L.; Rector, H. E. "Guidelines for monitoring indoor air quality,'' Environmental Protection Agency Report No. EPA-600/4-83-046,1983. 7. Bruno, R. C. "Verifying a model of radon decay product behavior indoors,'' Health Phys. 45: 471 (1983). 8. Mowris, R. J.; Fisk, W. J. "Modeling the effects of exhaust ventilation on 222 Rn entry rates and indoor 222Rn concentrations," Health Phys. 54: 491 (1988). 9. McCullough, R. P.; Letorneau, E. G.; Waight, P. J. "A four factor model for estimating human radiation exposure to radon daughters in the home," Health Phys. 40: 299 (1981). 10. Harley, N. H.; Pasternack, B. S. "A model for predicting lung cancer risks induced by environmental levels of radon daughters," Health Phys. 40: 307 (1981). 11. Hofmann, W.; Katz, R.; Chunxiang, Z. "Lung cancer risk at low doses of alpha particles," Health Phys. 51:477 (1986). 12. Nero, A. V.222"Indoor radiation exposures from Rn and its daughters: a view of the issue," Health Phys. 45: 277 (1983).
R. W. Sheets is a professor of Chemistry at Southwest Missouri State University, Springfield, MO 65804. This manuscript was submitted for peer review on September 14, 1990. The revised manuscript was received on January 3,1991.
459
Journal of the Air & Waste Management Association Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/uawm18
Structural Dependence of Diurnal Fluctuations of Radon Progeny in Residential Buildings Ralph W. Sheets
a
a
Southwest Missouri State University , Springfield , Missouri , USA Published online: 07 Mar 2012.
To cite this article: Ralph W. Sheets (1992) Structural Dependence of Diurnal Fluctuations of Radon Progeny in Residential Buildings, Journal of the Air & Waste Management Association, 42:4, 457-459, DOI: 10.1080/10473289.1992.10467006 To link to this article: http://dx.doi.org/10.1080/10473289.1992.10467006
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
ISSN 1047-3289 J. Air Waste Manage. Assoc. 42:457-459
Structural Dependence of Diurnal Fluctuations of Radon Progeny in Residential Buildings Ralph W. Sheets
Downloaded by [Case Western Reserve University] at 07:53 11 December 2014
Southwest Missouri State University Springfield, Missouri
Movement of radon progeny inside houses is a complex process that depends both on atmospheric conditions and on building structure. The indoor working level (WL) monitored in four houses of differing structures shows regular diurnal fluctuations related to solar warming of the atmosphere. In the two houses with full basements, radon is removed by indoor/outdoor pressure-driven airflow, and basement WL varies inversely with outdoor temperature. In the two houses with half basements open to crawl spaces, radon is drawn into the basement faster than it is removed, so that basement WL varies directly with outside temperature. Average WL's in basements are about twice as high as first floor WL's and as much as 18 times as high as outdoor WL's. Each house shows an individual pattern of radon progeny movement throughout the building.
Outdoor radon (222Rn) concentrations near the ground fluctuate diurnally, with minimum concentrations occurring in the afternoon and evening hours, and maximum concentrations during the night and early morning.1""^ These diurnal patterns are attributed to variations in atmospheric stability, and it has been established that outdoor radon concentration is a periodic function of solar heating.3 Similarly, measurements of indoor radon have shown regular diurnal fluctuations inside houses.1-4 Spitz4 reported a diurnal fluctuation in the basement of a New Jersey house similar to the outdoor pattern with a morning maximum and an afternoon minimum. Harley et al.5 found different diurnal patterns in the basements of two houses: in one a positive correlation was found between basement radon concentration and indoor/outdoor temperature difference; in the other a negative correlation was observed. It thus appears that indoor radon patterns are structure-specific. Measurements of radon in hundreds of resi-
dences throughout the United States, funded by the U.S. Environmental Protection Agency and other government agencies, have investigated relationships between indoor radon and structural properties. Many of these studies are summarized in collections and handbooks.6 Models have also been developed to predict behavior of radon and its decay products indoors,7'8 and to relate lung cancer risk to indoor radon concentrations.9"11 In order to assess the health effects of indoor radon, it is important to know whether basement levels generally correlate with outdoor patterns and whether levels in living areas correlate with basement and crawl space levels. Since human health consequences of long term exposure are related, not to radon itself, but to its short-lived decay progeny ( 218 Po, 214pb> 214 Bij
and
214p o) 12
i t ig
eyen
more important to know how indoor concentrations of these nuclides vary. This study was designed to answer some of these questions.
Implications Buildup and removal of radon and its lung cancer-inducing progeny in houses depends on the structure of the building as well as on meteorological conditions. Concentrations of radon decay products in many houses fluctuate regularly over a 24-hour period as outside temperature changes. The patterns of increase and decrease are not identical in all houses, or even in different parts of the same house. This structure-dependent behavior is important in assessing health effects of indoor radon pollution.
Experimental
Radon daughter levels of four houses in the city of Springfield, Missouri, were monitored (Table I). The houses all lie near the central part of the city, but are located at least one mile apart. All houses were continuously occupied during the study. Measurements were made under a variety of conditions (weather, ventilation, heating/cooling), and no attempts were made to control any of these variables. Indoor levels of radon progeny measured in this way better reflect real-life conditions than do measurements made in studies which attempt to control these variables. Continuous monitoring was carried out over periods of 3 to 6 days in several different months (November; March-June). Parameters measured include: outdoor temperature, pressure, and relative humidity; indoor temperature, pressure, and relative humidity; outdoor working level (WL) (a measure of total radon progeny concentration); and indoor WL. Working levels were continuously monitored by an Eberline monitoring system with alpha activity averaged over one-hour periods. The system consisted of two WLM-1A working level monitors and a WLR-1A readout unit. Air flow rates were calibrated with a flowmeter and the solid state alpha counters were calibrated with a 0.00493 microCurie (182 Bq) NBS-traceable 230 Th source. Usually two sites at each structure were monitored simultaneously (e.g., indoors/outdoors, or basement/first floor). Temperature, atmospheric pressure, and relative humidity were monitored by Cole Parmer recording instruments at the same locations as the working level monitors. All measurements were made at ground or floor level. Results and Discussion
For all parameters (WL, temperature, atmospheric pressure and relaCopyright 1992—Air & Waste Management Association
April 1992
Volume 42, No. 4
457
Downloaded by [Case Western Reserve University] at 07:53 11 December 2014
Table I. Description of houses monitored in Springfield, Missouri. House
Description
A B C D
Brick—One Story—Full Basement (Finished) Brick—One Story—Full Basement (1/2 Finished) Brick—One Story—1/2 Basement, 1/2 Crawl Space Frame—Two Story—1/2 Basement, 1/2 Crawl Space
30+ Years 30+ Years 30+ Years 30+ Years
tive humidity) regular diurnal patterns emerged when data collected for several days were averaged over a 24hour period. To a first approximation the diurnal fluctuations in pressure and relative humidity in the houses investigated were found to be inversely proportional to the diurnal fluctuations in temperature. Thus these parameters added little information beyond that provided by temperature measurements alone. Since average indoor temperatures were relatively constant, the relationship between WL
and outdoor temperature was examined. For comparison, outdoor WL and temperature values at House A collected for three consecutive days in June 1988, and averaged over a 24hour period (local standard time) are given in Figure 1. The inverse relationship between the two variables is clearly evident. Figure 2 shows indoor diurnal WL fluctuation together with the outdoor average temperature during a 9-day period in March and April 1988. The indoor WL patterns are
28
_
LOCAL STANDARD TIME (HR)
Figure 1. Diurnal fluctuation of outdoor working level (WL) and outdoor temperature at house A (three-day mean). WLB 140
TEMP
-
120
L 1OO
80
WLF
60
40
/
A
on
LOCAL STANDARD TIME (HR)
Figure 2. Diurnal fluctuation in working level (WLB), working level on first floor (WLF), and outdoor temperature at house A (nine-day mean).
458
seen to be similar to the outdoor patterns and are due to the same cause: solar heating of the atmosphere. The resulting decreased density of the outdoor air causes it to rise, diluting the outdoor WL and causing a decrease in outdoor pressure relative to indoor pressure. Airflow from the higher pressure indoor environment to the outside carries radon and its decay products out of the building, decreasing the indoor WL. Similar patterns are observed both in the basement and on the first floor. Anomalous behavior was observed during several early morning periods when outside temperature dropped below about 5°C. During these times, indoor WL's appeared to be directly related to outdoor temperature (Figure 2). This is due to convective flow of air out of the warm house, which causes a decrease in indoor WL. House A is a one-story brick building with a full, finished (occupied) basement. Simultaneous measurements were made in the basement and in the living room directly above during a 6-day period in March 1988. Measurements were made in the basement and in a bedroom above for three different 3-day periods in April 1988. Diurnal plots of all data were similar to Figure 2. In general, WL's in various parts of the house are directly proportional to each other and inversely related to the outdoor temperature. Minimum WL's occur around 4 pm (CST), corresponding to maximum outdoor temperature. Maximum WL's occur during the night. Correlation analysis shows R2 values of about 0.70.9. The higher correlations are obtained by offsetting the dependent variable to correct for the lag time inherent in measurement of the decay products of radon. The ratio of WL(Outdoor): WL(Bedroom):WL(Living Room):WL(Basement) was approximately 1:3:4:8. House B has a structure much like House A. It is a brick, one-story building with a full basement. Only half the basement is finished and occupied, however. The other half is enclosed in unfinished concrete. Measurements of WL and temperature made during May-June 1988 yielded diurnal plots very similar to Figure 2. Working levels in both parts of the basement and in a bedroom directly above the unfinished basement were directly proportional to each other and inversely related to outdoor temperature (R2 values of 0.7-0.8). The ratio of WL (Outdoor):WL(Bedroom):WL(Finished Basement) :WL(Unfinished Basement) was about 1:5:5:10. House C is also a one-story brick building, but its basement is different from Houses A and B. In House C, one-half of the house lies over an enclosed unfinished concrete basement, and the other half over an enJ. Air Waste Manage. Assoc.
Downloaded by [Case Western Reserve University] at 07:53 11 December 2014
closed, dirt-filled crawl space. There is a large opening (4 x 12 feet) which allows free interchange of air between the basement and crawl space. In House C, WL and temperature were monitored for a total of 44 days in November 1986 and March-May 1987. All diurnal plots are similar to Figure 3. The WL in a first floor bedroom above the basement shows the diurnal pattern found in Houses A and B. Minimum WL's are reached around 6-8 pm and maximum levels in the morning hours. Figure 3 shows that, unlike the other houses, diurnal WL fluctuation in the basement of House C varies directly with outdoor temperature and inversely with first floor WL. WL in the crawl space followed the basement pattern, being directly proportional to both outdoor temperature and basement WL. The average ratio of WL(Outdoor):WL(First Floor): WL(Basement):WL(Crawl Space) was about 1:6:12:18. The diurnal pattern observed in House C can be explained as follows: the outdoor/indoor pressure differential caused by afternoon solar heating results in convective flow of air out of the house. In the upper part of the house, which is shielded from the crawl space, radon and its progeny are drawn out of the house, reducing the WL. The same convective effect, however, draws air and radon gas from the soil in the crawl space and into the basement. The net effect is that radon and decay products enter the basement faster than they are removed. Table II. Dependence of indoor working level (WL) on outdoor temperature. Crawl Space
House A B C D
No Crawl Space No Crawl Space Direct Direct
Basement
First Floor
Inverse
Inverse
Inverse Direct Direct
Inverse Inverse Direct
20 LOCAL STANDARD TIME (HR)
Figure 3. Diurnal fluctuation of working level in basement (WLB), on first floor (WLF), and outdoor temperature at house C (six-day mean).
living room (above the basement) show weaker diurnal variations that appear to be positively correlated with outdoor temperature, and with the basement and crawl space WL's. Measurement of WL in two bedrooms of the second floor show no diurnal effect. In these rooms there is a rather constant, low level of radon progeny only slightly higher than the average outdoor level. The average ratio of WL(Outdoor): WL(Second Floor): WL(Living Room): WL(Dining Room):WL(Basement):WL(Crawl Space) is about 1:1:2:3:6:12. Table II summarizes diurnal WL patterns of the four houses included in this study. The results indicate that outdoor temperature (or indoor/outdoor temperature difference) has a large effect on indoor radon progeny concentrations. The effects do depend on specific structural variations, however, and these factors need to be kept in mind in designing laboratory models in applying results of model studies to real-life situations. Acknowledgment
A similar pattern is seen in House D. This house is a two-story frame house quite unlike the other three in construction. It is similar to House C in that it has a one-half unfinished basement which is open to an enclosed crawl space through two 3 x 3 ft holes. Monitoring of this house in April-June 1986 indicated that its WL pattern resembles House C more than Houses A and B. The crawl space and basement show a strong diurnal effect with maximum WL occurring in midafternoon and minimum values around midnight. In this house, maxima and minima in the basement lag 1-2 hours behind corresponding maxima and minima in the crawl space. The dining room (above the crawl space) and the April 1992
Volume 42, No. 4
This work was sponsored in part by the Air Force Office of Scientific Research, Boiling AFB, DC(S-760-OMG032). References 1. 222 Gesell, T. F. "Background atmospheric Rn concentration outdoors and indoors: a review," Health Phys. 45: 289 (1983). 2. U.S. Dept. of Energy, Indoor Air Quality Environmental Information Handbook: Radon, National Technical Information Service, Springfield, Virginia, 1986, pp. 2-24. 3. Garzon, L.; Juanco, J. M.; Perez, J. M.; Fernandez, J. M.; Arganza, B. "The universal Rn wave: an approach," Health Phys. 51:185 (1986). 4. Spitz, H. B.; Wrenn, M. E.; Cohen, N. "Diurnal Variation of Radon Measured
Indoors and Outdoors in Grand Junction, Colorado, and Teaneck, New Jersey, and the Influence that Ventilation has on Buildup of Radon Indoors," in Natural Radiation Environment III, U.S. Dept. of Energy, Special Symposium Series 51, CONF 780422,1980, p. 1308. 5. Harley, N. H.; Terilli, T. B.; Khademi, B. "Indoor radon related to indoor outdoor temperature difference," abstract in Thirty-Third Annual Meeting of the Health Physics Society, Health Phys. 54: (Supplement 1), Abstract WAM-F4 (1988). 6. Nagda, N. L.; Rector, H. E. "Guidelines for monitoring indoor air quality,'' Environmental Protection Agency Report No. EPA-600/4-83-046,1983. 7. Bruno, R. C. "Verifying a model of radon decay product behavior indoors,'' Health Phys. 45: 471 (1983). 8. Mowris, R. J.; Fisk, W. J. "Modeling the effects of exhaust ventilation on 222 Rn entry rates and indoor 222Rn concentrations," Health Phys. 54: 491 (1988). 9. McCullough, R. P.; Letorneau, E. G.; Waight, P. J. "A four factor model for estimating human radiation exposure to radon daughters in the home," Health Phys. 40: 299 (1981). 10. Harley, N. H.; Pasternack, B. S. "A model for predicting lung cancer risks induced by environmental levels of radon daughters," Health Phys. 40: 307 (1981). 11. Hofmann, W.; Katz, R.; Chunxiang, Z. "Lung cancer risk at low doses of alpha particles," Health Phys. 51:477 (1986). 12. Nero, A. V.222"Indoor radiation exposures from Rn and its daughters: a view of the issue," Health Phys. 45: 277 (1983).
R. W. Sheets is a professor of Chemistry at Southwest Missouri State University, Springfield, MO 65804. This manuscript was submitted for peer review on September 14, 1990. The revised manuscript was received on January 3,1991.
459
