Greetings and happy Friday.

I purchased an air filter to use with my Inspector Alert, and while it's been frustrating to get any of the data from the Inspector Alert online, I've been running it in my bedroom just to get a baseline. Average CPM with the unit in various places on its own is typical of what I see from a lot of other people - somewhere in the mid 30s.

If I rest the window of the GC near the intake of the air purifier where the filter is however, it typically reads between 160-200 CPM when the purifier is running. Without moving the GC, if I simply turn off the air purifier, the CPM again drops down to the mid 30s. This indicates to me that nothing substantially hot really got stuck to the filter.

What could be going on here? Radon seems unlikely, as this is on the second story of the building.

I suggest using a radon only digital detector like the safety siren to test.

I own two and they have helped me lots.

Is your heater in the basement?

Mine is and has I have proven that it does in fact bring the basement radon gas upstairs.

Thank you for the response! We do indeed have an ancient heater system, but it is rare to find anyone in California with a basement. It is possible that radon is being redistributed throughout our house. I will look into radon detectors and post results. The only thing detracting from this hypothesis, is that the variation of these readings are observed at every time of day/night when the heater is both on and off.

Another point of data, is that there is a lag between when the air filter is turned off and the GC returns to normal background of at least 30 minutes to an hour or two. It continues to read 160-200 CPM after the airflow stops, then settles back to around 35.

I looked up Safety Siren, and there are many models. Which one did you use, and which one would be best?

Thinking of getting this one, let me know if there is a better model.

http://www.amazon.com/Safety-Siren-Seri ... fety+siren

Without more info, we know not whether you have already checked/eliminated obvious things that might be unrelated to actual higher contamination readings due to greater volume of air per unit time being passed by the GC window. With the air filter running, Is the air velocity by the GC window increased enough that it distorts the mica window and thus somehow accounts for an artificially distorted measurement (not sure if such distortion is actually possible)? For example, have you tried things like comparing readings while the air filter is running with and without the filter installed?

Regarding time for the GC to go back to zero, is the unit's time averaging function influencing the delay? To check, did you, for example, immediately turn off the unit to zero it out, then turn it back on, to see if the reading goes right back up to where it previously was?

If it were indeed due to air filter contamination from (primarily) increased radon exposure then I would not necessarily conclude this is "nothing substantially hot", (even if the radon were to decay out and disperse within a couple of hours after turning the filter off).

That is the same model I have!

Try calling your local rental stores. Maybe you can get them to buy the unit and you can just rent it for 4 days or so for testing. Although if the money is no problem, I suggest buying it for real-time monitoring 24/7.

One possibility that comes to mind is that you are collecting alpha or beta particles on your filter that have a half-life of a few minutes to a few hours. If I remember correctly, I think that the common radioactive iodine isotopes fall into that category. I am not an expert here, just an idea that came up based on some of the things that I have read.

Another possibility is that the motor in the air cleaner somehow interferes with the detection circuitry in your GC. I think this is less likely though. What happens if when you get a high reading you turn off the air cleaner then turn off your GC for a minute or so and then turn it back on. Do you still get a high reading?

So I've left the setup running continuously over the weekend, and saw levels drop to 90 CPM and stay around there most of the time. There is little to no possibility of the mica window on my GC distorting the way it is positioned, which makes that first reading a bit of an anomoly. That is, until I saw it raising to 160+ again, when the heater was turned on. Will know more when I get the radon detector.

Just like I said. I noticed the same thing here in my home. In fact, this winter we have been using the kerosene heater more than ever. This keeps the radon downstairs and also reduces our electric bill down. Less electricity used is a protest against nuclear power.

Using a radon mitigation pump installed I have lowered our basements radon level from 18 pCi/L down to under 2 pC/L