Calculating Worker Exposure to Radon & Radon Decay Products

The exposure of radon workers to radon and RDP’s can be calculated with the units of measurement for radon (pCi/L), RDP’s (WL), and equilibrium ratio (ER). Occupational exposure to RDP’s is measured in Working Level Months (WLM). 

The following is considered when calculating WLM:

  • One WLM is the equivalent of exposure to 1 WL for 170 hours.
  • RDP measurement levels (in WL’s) are multiplied by the duration of exposure (in hours) divided by 170 to obtain exposure levels in WLM’s.

Example of WLM exposure record:

Exposure calculation in WLM: