Bests & Worsts Reviews from Amazon

I bought this gizmo a few weeks ago to monitor the basement in our new house and see if it is usable as an entertainment/gym area. In the summer when we did the radon test the result came in at 2.4 . When I first turned on this device the result came in at 8.4 !! That made me freak out a bit, but after re-reading the instruction I realized that placing the detector 2 feet away from the sump hole may not be the right thing to do. So, I moved it closer to the middle of the basement and reset it. After a couple of days the reading came in at 4.6 . During heavy rains the device showed readings of as high as 5.9 and it went down to 4.2 during dry weather. Before taking any drastic measures I decided to first do some common sense maintenance tasks on the basement to at least prevent radon from entering the living area upstairs. I taped up all the cracks in the HVAC ductwork that I could find. The radon reading slowly creeped up to 4.6 due to reduced ventilation of the basement, but at least none of it was going upstairs. I called our house inspector who did the test and he pointed out that when we inspected the house there were storage cabinets over the sump hole and along the walls, covering up the "mother earth." So I placed a piece of rubber tile over the sump hole and the reading when down to 3.2 in a couple of days. So, what's the moral of this story ? While I can't vouch for precision of this device I learned the following: - You need to leave it on for at least a month before you get an accurate reading. - There is no need to freak out over "mildly" high readings. First, the device is not that accurate. Professional continuous testing devices cost thousands. So, don't take what it says as an absolute measure. Trust, but verify. Second, the US EPA requires mitigation at 4.0 -- but based on my research European agencies require mitigation at 7.0 and in some parts of Canada as high as 20.0 . - If the reading is mildly high, say between 4 and 6 like it was in my case, then common sense maintenance tasks may take care of the problem. For example, covering up the sump hole with a piece of rubber tile helped bring the reading down to under 4.0 for us. What radon mitigation people don't tell you is that you can cut your radiation exposure in half just by circulating the air in your basement. Moving the air around encourages the plate-out (settlement) of charged daughter particles of radon decay. It doesn't reduce the radon itself, but it encourages the actual dangerous stuff to stick to the walls and furniture instead of your lungs. The decay of the daughter particles is measured in minutes, and not even days. There is a guy who patented a ceiling fan as a means of mitigating radon. So, the point is -- mild increases in radon levels can be mitigated cheaply, if not for free. To conclude, I find this device useful in general as a tool for measuring earth gases entering the basement. Besides radon there is a lot more harmful stuff that may be seeping in that you need to worry about. Ground water carries all sorts of disgusting stuff and in some areas of the country mildly high radon levels are the least of your worries (think arsenic, mercury, MTBE, etc.) So, if the Safety Siren is telling you you have mildly high radon readings it probably means you have mildly high levels of all sorts of other disgusting crap in your basement. Common sense methods of circulating the air, covering up the exposure to dirt, etc. is enough to control the problem. UPDATE 3/4/09: I realized that I had the device's power supply right next to it. Moving it away from the unit lowered the radon reading by at least 1.0-2.0 pCi/L . It is now consistently below 4.0 . This is a finicky little gadget. I wouldn't rely on it as the source of all truth about radon. TRUST BUT VERIFY.