radioactive furnace filter

After your repeatedly getting insanely High readings during the day every day I decided to check my old furnace filter as I was getting ready to throw it out. I first measured background radiation using an sbm 10 at 110 counts per minute (large sensitive tube). Even took a one minute count with me Geiger tube on the intake side of the furnace filter it gave me a reading of 910 counts per minute 800cpm higher than my current background. I realize that dust will have some radioactive component to it but to me this seems incredibly High. Does anyone have any thoughts or information on this.

Steve

If the furnace filter was catching Radon 222 decay products just before removal, the readings should have dropped steadily over the following 8-16 hours. Radon itself would likely pass right through, but the 3 next decay products (Lead, Bismuth and Polonium) are solid and would tend to stick to dust particles, which would get caught in the filter (especially if it were a HEPA filter). These have a half life totaling about 50 minutes and would be giving off both Alpha and Beta particles. I see your post is 20 hours old. Is the filter still hot? If so, it would be something else. You can send it for free analysis to http://www.radtest4u.com/ .

Be very careful with the filter dust. Breathing it in before it decays would expose you to unnecessary radiation.

I should have mentioned in my post my filter is a HEPA filter I'm running one of the highest efficiency filters I could find (due to allergies.) I put the same filter back in I'll pull it take readings and take readings every 6 hours or so and see what happens. Thank you for the info on free testing I was considering trying to contact the EPA. if these are radon Decay products would there still be anything in the filter for them to test by the time someone gets it for a testing? As I mentioned in another post after looking at a map of the country for radon I am in an area that has one of the highest radon levels On the map. As far as being careful with the filter unfortunately this is the same air I breathe 24/7. while I don't think it has anything to do with my readings I am within 15 miles of the nearest nuclear power plant it Byron Illinois. After I've tested it for about twenty-four hours I'll post the test results of 6 hour readings on the filter.

Thanks,
Steve

I pulled the furnace filter out this morning and tested it at a thousand counts per minute with a current background of around 200 CPM. Within 4 to 5 hours it dropped back off to background. I guess this must be radon Decay products.

It's good that you're using a high quality HEPA filter. They were initially developed to stop radioactive dust from being breathed in, and they are even better now. By taking the small particles out of the air we don't breathe them in, but I notice that when I dispose of my own filters, if I'm not careful I can make a puff of concentrated dust. That is a big risk in a Radon-prone area. Old dust would still contain Lead-210 which, though far less radioactive, is dangerous enough to breathe as dust. The test lab would likely be able to identify Lead-210 and thereby confirm Radon decay products.

If you are considering Radon mitigation, which consists of vacuum pipes to remove gas from below the basement floor before it enters, this video features one such installation: https://www.thisoldhouse.com/how-to/how-to-install-radon-mitigation . There are several companies selling mitigation systems.