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Health Physics
March 2014, Volume 106, Number 3
REPLY TO THOMAS
Fig. 1. The variability of F with k or a0o.
(k = the ventilation rate and aio = the atmospheric radon progeny concentrations). However, both quantities are variable only in a short range, so this approach promises success. The value a210Po = 500 mBq mj (UNSCEAR 2000) was used. RESULTS Summarized results of the direct evaluation of the experimental data for the room H5 are given in Table 1 and compared with results from eqn (1). The variability of F with k or a0o is not strong and not of weight, as can be seen from Fig. 1. Decreasing the value of a4o, e.g., down to 400 mBq mj3, decreases the value of F only 2%. The dependence of k on k is conversely very fast, and positive values are obtained only for k e -0.2 hj1 without dramatic changes of F. CONCLUSION The average value F = 0.84 T 0.01 is the result of the alternative evaluation. This value is 9% higher, but not significantly higher, than the relevant value F = 0.77 in eqn (1) for the room H5 and not lower as was expected. So it can be concluded that the less appropriate model and the approximate method of evaluation probably are not the reasons for the high value of the equilibrium factor obtained from long time sampling; another explanation has to be found. Lower values of F can be obtained from lower activities of 210Pb or 210Po; e.g., the contribution of shortand long-lived thoron progeny has to be analyzed as well as other experimental conditions by Harley et al. (2012).
Dear Editors: THERE ARE several ways to calculate the radon equilibrium factor, Feq, from our long-term airborne measurements of 210Po in six homes and two laboratories. The measurements were mainly in basements, and Feq is expected to be greater than for other living areas and is commonly chosen as 0.4. We measured the 210Po on the filters sequentially over several months to observe 210Po buildup from 210 Pb and calculated the 210Pb activity on the filters at end of sampling from the average of the measurements. The alternate calculation of Thomas resulted in a value of Feq in House 5 of 0.84 versus our value of 0.77. Thomas believes there is a contribution of outdoor radon decay products to the basement air and estimates the total exchange rate for wall deposition, ventilation, from eqn (7). Harley et al. comments on the Thomas estimation of Feq for house 5: 1. The assumption of a significant contribution from radon progeny from outdoor air is not supported. The Thomas Table and Figure show that kappa (which includes radon progeny from outdoor air) is essentially zero for a ventilation rate of 0.2 hj1. The ventilation rate in this basement is likely somewhat greater than 0.2 hj1. Most important is the fact that in a cold climate such as Canada, basement windows are normally sealed; at least this was the case for all homes tested in this study. Indoor air continually exchanges with fresh outdoor air through a forced-air heating system. The air filters in this forced-air heating system prevent radon progeny from entering the house; 2. The outdoor radon concentrations used in Table 1, 1 and 10 Bq mj3, are low. An outdoor radon concentration larger than 10 Bq mj3 is better for the U.S and Canada; and 3. Thomas states, ‘‘A contribution of thoron progeny to our measurements has to be analyzed.’’ A thoron progeny contribution to our measurements is not possible as no long-lived species exists. The author declares no conflicts of interest. NAOMI HARLEY
The author declares no conflicts of interest. J. THOMAS National Radiation Protection Institute Praha, Czech Republic
New York University School of Medicine Dept. Environmental Medicine 550 First Avenue New York, NY 10016
REFERENCES
REFERENCE
Harley NH, Chen J, Chittaporn P, Sorimachi A, Tokonami S. Long term measurements of indoor radon equilibrium factor. Health Phys 102(4):459Y462; 2012. UNSCEAR 2000, Sources, Annex B.
Harley NH, Chen J, Chittaporn P, Sorimachi A, Tokonami S. Long term measurements of indoor radon equilibrium factor. Health Phys 102:459Y462; 2012.
www.health-physics.com
Copyright © 2014 Health Physics Society. Unauthorized reproduction of this article is prohibited.
¡¡
Health Physics
March 2014, Volume 106, Number 3
REPLY TO THOMAS
Fig. 1. The variability of F with k or a0o.
(k = the ventilation rate and aio = the atmospheric radon progeny concentrations). However, both quantities are variable only in a short range, so this approach promises success. The value a210Po = 500 mBq mj (UNSCEAR 2000) was used. RESULTS Summarized results of the direct evaluation of the experimental data for the room H5 are given in Table 1 and compared with results from eqn (1). The variability of F with k or a0o is not strong and not of weight, as can be seen from Fig. 1. Decreasing the value of a4o, e.g., down to 400 mBq mj3, decreases the value of F only 2%. The dependence of k on k is conversely very fast, and positive values are obtained only for k e -0.2 hj1 without dramatic changes of F. CONCLUSION The average value F = 0.84 T 0.01 is the result of the alternative evaluation. This value is 9% higher, but not significantly higher, than the relevant value F = 0.77 in eqn (1) for the room H5 and not lower as was expected. So it can be concluded that the less appropriate model and the approximate method of evaluation probably are not the reasons for the high value of the equilibrium factor obtained from long time sampling; another explanation has to be found. Lower values of F can be obtained from lower activities of 210Pb or 210Po; e.g., the contribution of shortand long-lived thoron progeny has to be analyzed as well as other experimental conditions by Harley et al. (2012).
Dear Editors: THERE ARE several ways to calculate the radon equilibrium factor, Feq, from our long-term airborne measurements of 210Po in six homes and two laboratories. The measurements were mainly in basements, and Feq is expected to be greater than for other living areas and is commonly chosen as 0.4. We measured the 210Po on the filters sequentially over several months to observe 210Po buildup from 210 Pb and calculated the 210Pb activity on the filters at end of sampling from the average of the measurements. The alternate calculation of Thomas resulted in a value of Feq in House 5 of 0.84 versus our value of 0.77. Thomas believes there is a contribution of outdoor radon decay products to the basement air and estimates the total exchange rate for wall deposition, ventilation, from eqn (7). Harley et al. comments on the Thomas estimation of Feq for house 5: 1. The assumption of a significant contribution from radon progeny from outdoor air is not supported. The Thomas Table and Figure show that kappa (which includes radon progeny from outdoor air) is essentially zero for a ventilation rate of 0.2 hj1. The ventilation rate in this basement is likely somewhat greater than 0.2 hj1. Most important is the fact that in a cold climate such as Canada, basement windows are normally sealed; at least this was the case for all homes tested in this study. Indoor air continually exchanges with fresh outdoor air through a forced-air heating system. The air filters in this forced-air heating system prevent radon progeny from entering the house; 2. The outdoor radon concentrations used in Table 1, 1 and 10 Bq mj3, are low. An outdoor radon concentration larger than 10 Bq mj3 is better for the U.S and Canada; and 3. Thomas states, ‘‘A contribution of thoron progeny to our measurements has to be analyzed.’’ A thoron progeny contribution to our measurements is not possible as no long-lived species exists. The author declares no conflicts of interest. NAOMI HARLEY
The author declares no conflicts of interest. J. THOMAS National Radiation Protection Institute Praha, Czech Republic
New York University School of Medicine Dept. Environmental Medicine 550 First Avenue New York, NY 10016
REFERENCES
REFERENCE
Harley NH, Chen J, Chittaporn P, Sorimachi A, Tokonami S. Long term measurements of indoor radon equilibrium factor. Health Phys 102(4):459Y462; 2012. UNSCEAR 2000, Sources, Annex B.
Harley NH, Chen J, Chittaporn P, Sorimachi A, Tokonami S. Long term measurements of indoor radon equilibrium factor. Health Phys 102:459Y462; 2012.
www.health-physics.com
Copyright © 2014 Health Physics Society. Unauthorized reproduction of this article is prohibited.
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