Air filter to catch radioactive particles - suggestions please

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8 years 10 months ago #1292 by bethsalem
I've used an activated carbon filter to test rainwater indirectly for radon washout and so this is just an extension of that.

Thanks for all your ideas. At the moment I think the cheapest, least hassle option is to buy a home air purifier, leave it outside in a sheltered spot where the rain can't get at it, and then test its HEPA filter regularly for increases in radioactivity.

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8 years 10 months ago #1297 by bethsalem
Just had another thought.

As my idea was not continuous detection, but rather testing the filter on a daily basis. Could I then use the much cheaper option of buying a handheld vacuum cleaner with a hepa filter?

The vacuum could be used to vacuum external surfaces of settled dust, which would stick to the hepa filter. Also the hepa filter would be the perfect size for testing purposes.

Any thoughts? Good plan or a rubbish idea?

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8 years 10 months ago #1298 by Bert490
That would probably work, but I think a continuous filter would more reliably detect a passing cloud of radioactive particles. I would worry about a settling area being blown clean before the vacuum gets there, or that the settling rate varies with wind speed. A continuous fan would probably catch more particles, and the filter could be sampled either periodically or continuously. Amazon advertises Sunbeam, Holmes or Honeywell tabletop fans that are pretty reasonable.

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8 years 9 months ago #1330 by bethsalem
I've finally got my hands on an air purifier with a HEPA type filter (99% of particles 2 microns and larger), but which can also use a true HEPA filter (99.97% of particles 0.3 microns and larger). The air purifier is the Bionaire BAP9240 (just google it).

It's incredibly easy to check the filter. It's just a matter of unclipping a latch and then full access to both filters to check for radioactivity :) It came with a washable foam pre-filter, but I've ditched that and replaced it with a much more efficient activated carbon pre-filter cannabalised from a cooker extractor hood :lol:

It's only designed for interior use, so at the moment the best I can do is position it in front of an open window in order to sample the outside air just as it enters the building.

So far (thankfully), nothing above the background cpm

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8 years 9 months ago - 8 years 9 months ago #1331 by mw0uzo
Modify the filter so the tube is inside it and connect to a kit geiger counter. Initially, it could provide a warning for when anything is drawn in or detected.
I wonder if a feature could be added to RadLog to output a signal to start the fan every 15 minutes for 5 minutes... perhaps by the serial port/usb. Then count over 10 minutes for accurate reading. RPi might be good for that with a modified Pyradmon.
Last edit: 8 years 9 months ago by mw0uzo.

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8 years 9 months ago - 8 years 9 months ago #1332 by mw0uzo
[ On the topic of RadLog, I think I will trim some features to aid the next release, its been too long and I haven't had much time to work on all the new stuff and fix the bugs/write the boring gui stuff. ]
Last edit: 8 years 9 months ago by mw0uzo.

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