denotes the concentration of 218Po in pCi/L;
denotes the concentration of 214Pb in pCi/L; and
denotes the concentration of 214Bi in pCi/L.
PAEC can be computed from concentration measurements of the short-lived thoron progeny in air
denotes the concentration of 212Po in pCi/L; and
denotes the concentration of 212Bi in pCi/L.
Another acceptable method for workplace monitoring of exposure to radon progeny is to measure
the Rn itself, and convert it to PAEC using known equilibrium factors. DOE's 10 CFR 835 permits
calculating equilibrium equivalent concentration, EEC, from radon concentration measurements, C,
based on knowledge or assumption of an equilibrium factor, F:
If F has not been measured, it is acceptable under some circumstances to assume a default indoor value of
FRn = 0.4 (UNSCEAR 1988, 1993; ICRP 1993a). If C is in units of :Ci/mL, then EEC will also be in
units of :Ci/mL (note: 1 pCi/L = 10!9 :Ci/mL).
For 222Rn, FRn is defined as
= the concentration of 218Po;
= the concentration of 214Pb;
= the concentration of 214Bi; and
= the concentration of 222Rn.
For 220Rn, FTn is defined as