Answer to Question #9462 Submitted to "Ask the Experts"

Category: Environmental and Background Radiation — Radon

The following question was answered by an expert in the appropriate field:


Is there any mathematical way to find the working level (WL) when we know only the concentration of radon in becquerels per cubic meter (Bq m-3) in a workplace?


I know of no mathematical formula that will convert radon concentration to WL in a workplace. If radioactive decay was the only removal method for the short-lived radon progeny, secular equilibrium would exist between the radon and its progeny after a few hours. Then:

         WL = Rn concentration (Bq m-3) x 0.00027

In a workplace, however, there are other removal mechanisms for radon progeny. Radon decay products usually have an electrostatic charge and can attach to walls, furniture, windows, rugs, etc. The attachment of radon decay products to surfaces in a room increases with increasing air movement. Forced circulation by fans will reduce radon progeny concentrations. Radon decay products can also be reduced by filtration and ionization devices (Moeller et al. 1988). Atmospheric dust concentration can influence removal. Removal of the progeny by means other than radioactive decay results in the WL being less than that given in the equations above. This fractional reduction is known as the equilibrium factor (EF) and cannot be calculated by a formula because of the variety and complexity of radon progeny removal mechanisms; therefore, the WL cannot be calculated. Typically, the EF is either assumed (typically 0.4 to 0.5 for residential situations) or determined experimentally by simultaneous measurement of radon concentration and WL.

The following link leads to a discussion of the relationship between radon concentration and WL: A Living Radon Reference Manual

Tom Gesell, PhD

Moeller DW, Rudnick SN, Maher EF. Laboratory and field tests of a hassock fan-ion generator radon decay product removal unit. Radiat Prot Dosimetry 24 (1-4):503-506; 1988.

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