Jim, You might find the discussion in Wikipedia useful: http://en.wikipedia.org/wiki/Radon
Look about 1/3 down the page in concentration units. It discusses the issue of measuring just the radon or radon and progeny. The WL units are disguised measurements of total radioactivity energy (rather than number) per liter. While this helps, I'm still a little confused, so no tough questions, OK. :) ________________________________ From: James R. Frysinger <[email protected]> To: U.S. Metric Association <[email protected]> Sent: Fri, February 12, 2010 3:15:50 PM Subject: [USMA:46611] Can it get any harder? I've been investigating the problem of radon buildup in homes in our area. We live in a karstic limestone region in the Eastern Highland Rim of the Nashville basin, just at the western edge of the Cumberland Plateau. Our county seat, Spencer, is on the plateau and located 7 km SE of our home. We have a basement, so this is more than idle curiosity. The State of Tennessee provides free testing (as does the National Safety Council. The stated level of radon activity at or above which action is recommended is 4 pCi/L or 0.02 WL. Now, I understand curies and the radioactivity of radon. It's too bad that the EPA and other federal and state agencies haven't shifted to using becquerels yet, but that's another matter. But what about "0.02 WL"? I found it at http://www.nsc.org/safety_home/BringSafetyHome/Documents/Radon%20FAQ.doc and it says: [quote] What is a "working level" (WL)? Some devices measure radiation from radon decay products, rather than radiation coming directly from radon. Measurements from these devices are often expressed as WL. As noted above, conversions from WL to pCi/L are usually approximate. A level of 0.02 WL is usually equal to about 4 pCi/L in a typical home. If a working level (WL) value is converted to a radon level (pCi/L), the conversion is usually approximate and is based on a 50 percent equilibrium ratio. If the actual equilibrium ratio is determined (which is rare), it should be stated. The 50 percent ratio is typical of the home environment, but any indoor environment may have a different and varying relationship between radon and its decay products. Technically speaking, 1 WL represents any combination of short-lived radon decay products in one liter of air that will result in the ultimate emission of 1.3 x 105 MeV of potential alpha energy. [end quote] That latter figure is obviously 1.3 × 10^5 MeV. Working level? Couldn't the National Safety Center and Environmental Protection Agency come up with a more "hoo-doo" unit of measurement? So, what is 1 WL? 200 pCi/L? Who would want to work in THAT environment? I've sent off for a free test kit from the State of Tennessee's Department of Environment & Conservation. In the meantime, I intend to keep on working in my basement level (BL), which is the location of my workshop. I do encourage everyone to check the maps to see if they shouldn't get a free test done. Face it, your tax dollars have already paid for everyone else's. Jim -- James R. Frysinger 632 Stony Point Mountain Road Doyle, TN 38559-3030 (C) 931.212.0267 (H) 931.657.3107 (F) 931.657.3108
