Detector locations to avoid, to prevent a biased reading?


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ShortlegCats
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Message 1533 - Posted: 21 Dec 2012 | 6:26:27 UTC

For the detector placement, is there a list here already of items and locations within one's dwelling / building to avoid?

Clearly the idea here is to provide a measurement which is not already being influenced from something radioactive within one's dwelling, such as Krypton-85 in building windows, granite counter tops, etc.



Jason Taylor
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Message 1848 - Posted: 6 Jul 2013 | 1:45:33 UTC - in response to Message 1533.

Florescent lights and smoke detectors (from the roof on the floor below if you place it on your floor) may contain radioactive matter and can increase count rates. Basement will get a lower count than top floor.

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Message 1852 - Posted: 6 Jul 2013 | 10:57:26 UTC

Florescent lights: Are they react with the detector too, when they are off?

Whats the minimum distances to these things like the light and the smokedetectors?
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Message 1869 - Posted: 9 Jul 2013 | 12:31:48 UTC

the smoke detectors contain very small amount of Americium-241 so its activity is around 37 000 Bq, according to this source:
http://www.world-nuclear.org/info/Non-Power-Nuclear-Applications/Radioisotopes/Smoke-Detectors-and-Americium/#.Udv7cpzYeqs

only 0.3 micrograms. They also say:

Am-241 emits low energy gamma rays of 60 keV. The Am-241 gamma dose constant of 3.14 mSv/hr at a distance of one metre from a certain amount - 37 GBq - of Am-241. This gives an annual dose at one metre of 27 µSv/yr for an average household smoke detector – around 100 times lower than the dose from natural background radiation.


However,
we have here a few those elements from smoke detectors in total activity about 75 000 Bq so I did a practical test with our portable detector:
https://www.saic.com/products/security/pdf/gr-135_30Jun10.pdf

In direct contact I got values about 0.5 microSv/h but in 1 meter distance there was nothing - I measured normal background.

So I would say if the smoke detector is on the ceiling then you do not have to worry about it. :-)

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Message 1972 - Posted: 18 Aug 2013 | 12:02:09 UTC
Last modified: 18 Aug 2013 | 12:06:54 UTC

For smoke detectors: Not all have a radioactive source, mine don't have it. It's just in cheap, old stuff, good new stuff is optical. They are problematic, as they have to be disposed as radioactive waste, and must not enter the ordinary waste bin, at least here in Europe.

Edith says:
Old TV-sets and monitors, those with CRT, not LED/LCD, also emit radiation. I tested it with my sensor once, and it quadrupled the amount shown in the display if I got the Geiger-tube within a few centimetres from the screen.
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ShortlegCats
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Message 2002 - Posted: 5 Sep 2013 | 6:14:18 UTC

Thanks for the replies!

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