Page 700 - Radiation Safety
P. 700
SOURCES OF RADIATION EXPOSURE
WORKING LEVEL (WL) – unit for radon daughters
concentrations in air
• 1WL = combined short-lived radon daughters in 1L of air that produce potential α
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energies of 1.3 x 10 MeV. A smaller unit, mWL is also used.
• Working Level Month (WLM) = unit of exposure to radon or thoron daughters for 170h.
• Annual limits for workers: 4 WLM for radon & 12 WLM for thoron daughters