Appendix r CHANGES IN p DURING NONEQUILIBRIUM CONDITIONS The rapid changes in the RaC/RaB atom ratio (p) encountered in the chamber studies immediately after the addition of radon necessitated the developmentof new tables relating the growth and decay of radon daughteractivity collected during 20-min filtration periods to the radon concentration in the air. Such an approach was not required for determinations of atmospheric radon, since in that case it was assumed that the atmosphere could be considered to be in or near a state of dynamic equilibrium during periods of 20-min duration. Calculations of the collection and growth of RaA, RaB, and RaC ona filter during a 20-min collection were made taking into account the changes in RaA, RaB, and RaC occurring in the air prior to and during filtration. These changes are a function of the time during which the radon daughter products have been growing into equilibrium. The decay of these activities on the filter following ter- mination of collection and taking into account the successive decay of members ofthe series is shown in Table Al for collections made during periods of growth of the radon mixture corresponding to ages of 0-20 min, 40-60 min, 80-100 min, and infinite age (secular equilibrium established). The data used to construct working curves for determination of p and the radon concentration are contained in Table A2. 14 Application of the information contained in Tables Al and A2 to the results of the chamber studies does increase the accuracy of radon determinations during early states of growth of the radon daughters; however, its affect on the determination of g is not of great significance. A comparison of the results of the small chamber run based both on the standard procedure and on this more realistic procedure is shown in Table A3. Only during periods of low p values are any substanual differences noted in the derived radon concentrations. In addition to the comparison of the experimen- tal values of p and radon concentration for the two procedures, the expected values are also indicated; the experimental values of p {by either procedure) and the expected values are in good agreement, while the measured radon concentrations are about 50% low. This latter result is attributed to a “wall effect” due to the large surface-to-volume ratio and to the mechanical mixing within the chamber making the walls more accessible to impingement of diffusing ions and unattached atoms. The sampling process itself removes 11.8% of the aerosol and radon daughters with each collection, which results in effectively 6% of the radon being in a daughter-free, unmeasurable conditon during any coliection.