letters multiplied by the decay rate constant kz, yields the amount of radioactivity produced by inside radon.
Radon in a Leaky Home
To the Editor: There is a problem with R. Bruce Martin's otherwise informative article, "Radon in the Home" [J. Chem. Educ. 1991, 68, 2751 in the discussion of air exchange rates in houses. The author's calculations, based on air replacement times of 14 day, show possible radon buildup of as much as 94% of the theoretical maximum. Actually air exchange rates in most houses appear to be of the order of 0.25-1.5h (air renlacement times of 0.03-0.17 dav) ..(.I .) . Thus, calculations;sing arti in's model and more realistic air exchange rates yield maximum buildup of 3% or less. Literature Cited 1. Meyer, 8.Indmr Air Quality;Addison-Wesley: Reading, MA, 1983: p 6
Ralph W. Sheets Southwest Missouri State University Springfield,MO 65804
To the Editor: While my original article specifically refers to "closed homes", Sheets has introduced the problem in terms of "leaky homes", where inside radon leaks out through doors, windows, and cracks. We may easily and instructively extend our analysis to leaky homes in the following way. To the previous scheme we add a rate term for a leaky home, Rni + Out where inside radon, Rni, exits without return with the specific frst-order rate constant k,. The rate of appearance of inside radon still depends on the diffusion rate constant, kd, of outside radon, R h , into the house, and the radon radioactive decay rate constant, k z , according to
Again integrating between the limits 0 and [RnJ at times 0 and t we obtain the quantity of inside radon that, when
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Radioactivity amount =
As before the rate constant k l refers to the rate of radon production outside the home and defines the potential maximum amount of radioactivity for rapid diffusioninto a particular sealed home. There are now four limiting cases depending on the relative magnitudes of the three firsborder rate constants in the denominator. When k z >> k,, the latter rate constant drops out, and we have the same equation and the same two limiting cases discussed previously. Two new limiting cases arise when kz > kd most of the radon decays to solid products while still outside the home, and this favorable case poses no difficulties. When kz
