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 Geiger Detection Rates - Air Purifier vs. No Air Purifier 
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Joined: Mon Jan 28, 2013 7:40 pm
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Location: Illinois
:idea: If you have a geiger counter and are currently taking air sample readings, are you using an air purifier to increase detection rates?

If not look at the graph below. The geiger counter used was the GMC-200 and the air purifier used was a Holmes model with a HEPA filter like this one:

http://www.amazon.com/Holmes-HAP242-UC-HEPA-Desktop-Purifier/dp/B0000DK35B/ref=sr_1_2?ie=UTF8&qid=1384623564&sr=8-2&keywords=holmes+air+purifier

The geiger was put upside down near the bottom of the intake filter. This is because the GM tube in the GMC-200 in located at the bottom of the geiger counter and I wanted the tube to be closest to the largest area of the air filter which collects/traps the radioactive hot particles. The three plastic braces on the air purifiers filter were cut off to allow the geiger counter to sit flush against the filter. I recommend this purifier because Holmes like other companies change models but the same size filter has been used for over 10 years worth of models and can be bought at any WalMart.

Image

_________________
MY OUTSIDE RADIATION MONITORING STATION:
South Beloit, Illinois - GMC200 Outside on HEPA air purifier, ground level, facing West.
http://netc.com/chart/view.php?n=1%3AEB5A139C


Sat Nov 16, 2013 12:29 pm
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Why is outside air beta radiation detection so important?

ABC Channel 10 News wrote:
"We should take this very seriously," said Joseph Mangano, the executive director of the New York-based Radiation and Public Health Project, which researches the impact of nuclear power.

The group obtained results of eight air samples conducted by the EPA in San Diego in the month and a half after the nuclear disaster began.

It found that beta radiation levels in San Diego were more than six times the normal amount. While those are still low levels, the group says its numbers show the radiation may have harmed children.


http://www.10news.com/news/study-says-fallout-from-nuclear-disaster-in-fukushima-japan-may-be-harming-local-infants-04042013

_________________
MY OUTSIDE RADIATION MONITORING STATION:
South Beloit, Illinois - GMC200 Outside on HEPA air purifier, ground level, facing West.
http://netc.com/chart/view.php?n=1%3AEB5A139C


Tue Nov 19, 2013 10:47 am
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Joined: Fri Nov 22, 2013 5:31 pm
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Hi,

I'm new to this. I appreciate the diligent efforts you are putting into your monitoring efforts, and your willingness to share info.

I have some questions regarding the use of an air filter to increase the sensitivity of your GC measurements. Does not the air filter trap some radionuclide contaminants that do not rapidly decay away? If so, the measured levels (CPM) will rise as contaminants increase, no? Consequently, your baseline levels will continue to 'artificially' rise as the filter becomes more contaminated. Short of frequently (e.g., daily) changing out the air filter, how then do you distinguish between contamination that is newly hitting the filter, versus contamination that remains on the filter from previous contamination episodes? Further, how would you distinguish previous contamination that decays away before filter change-outs?

Thanks,
JohnD


Fri Nov 22, 2013 5:44 pm
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JohnD wrote:
Does not the air filter trap some radionuclide contaminants that do not rapidly decay away?

Most do start to decay away rapidly, this pattern can be seen on my charts. The stuff that does not decay away rapidly would likely be some really bad stuff and I would need a good amount of it to see a large rise. If I seen that, I would change the filter and check it daily for decay rates.

JohnD wrote:
If so, the measured levels (CPM) will rise as contaminants increase, no? Consequently, your baseline levels will continue to 'artificially' rise as the filter becomes more contaminated.


Remember, radon starts to decay away fast. Yes but it is only this increase in the hot particles by using the air purifier (contaminants as you called them) that allows a geiger counter like this model to clearly detect it. Pancake models are clearly better at detection but the GM tube of a pancake model geiger counter has only a 90 day warranty and $200+ to replace it. A pancake unit is hardly the kind of unit I want to leave outside.

JohnD wrote:
Short of frequently (e.g., daily) changing out the air filter, how then do you distinguish between contamination that is newly hitting the filter, versus contamination that remains on the filter from previous contamination episodes? Further, how would you distinguish previous contamination that decays away before filter change-outs?


I can distinguish between the new contamination because the old always seems to decay away leaving the filter ready to collect the next samples. I use this unit mainly to tell me if there is a rise of radiation outside above my previously recorded normal levels for my area. When it decays on the filter than it should have decayed in the yard too and therefore that would be the best time to let the kids play outside.

For me it is simply radiation mitigation. I do not have the time or the best gear to identify the isotopes on the filter or in a rain sample. I believe less radiation is best so I just try to avoid it. My air purifier system helps me do just that.

You can easily test for it yourself, the geiger counter GMC-200 is $85 and the purifier I use is $35:

http://www.amazon.com/Holmes-HAP242-UC-HEPA-Desktop-Purifier/dp/B0000DK35B/ref=sr_1_2?ie=UTF8&qid=1385210207&sr=8-2&keywords=holmes+air+purifier

_________________
MY OUTSIDE RADIATION MONITORING STATION:
South Beloit, Illinois - GMC200 Outside on HEPA air purifier, ground level, facing West.
http://netc.com/chart/view.php?n=1%3AEB5A139C


Sat Nov 23, 2013 7:30 am
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Hi JohnD

Quote:
I have some questions regarding the use of an air filter to increase the sensitivity of your GC measurements. Does not the air filter trap some radionuclide contaminants that do not rapidly decay away? If so, the measured levels (CPM) will rise as contaminants increase, no? Consequently, your baseline levels will continue to 'artificially' rise as the filter becomes more contaminated. Short of frequently (e.g., daily) changing out the air filter, how then do you distinguish between contamination that is newly hitting the filter, versus contamination that remains on the filter from previous contamination episodes? Further, how would you distinguish previous contamination that decays away before filter change-outs?


When you go outside and get exposed to radiation on your clothes, then you continue to receive radiation as long as you wear the clothes. Give the filter a break, it not human and can not change itself.
Harlan


Sat Nov 23, 2013 9:26 am
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High KingCobra,

Is it ever the case that when you change out the filter, you immediately see perceptibly lower count rates on the GC, which would probably be indicative of the previously used filter having some residual, 'longer half-life' radioactive contaminants? Have you ever then subjected the used filters to a closer inspection with a pancake alpha detector and consequently indeed found residual 'nasty' stuff'.

Quote:
The stuff that does not decay away rapidly would likely be some really bad stuff and I would need a good amount of it to see a large rise.


The concern then is having just a relatively small amount of the bad stuff accumulating over time (before filter change-outs), slowly distorting the baseline background measurement.

Maybe one possible way of 'normalizing' the measurements--in oder to take into account residual filter contaminants that could distort the daily background baseline measurement-- would be to have two of these relatively inexpensive geiger counters running in parallel, with one on a filter and one not (but have both experience the same air volume exchange), and then have the computer compute the difference between the two measurements. This concept could be extended, for example, to have three (or more) running in parallel (but possibly physically placed in-series), with and without filtration (and/or different types of filtration), etc.

Peace.


Sat Nov 23, 2013 9:48 am
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JohnD wrote:
Is it ever the case that when you change out the filter, you immediately see perceptibly lower count rates on the GC, which would probably be indicative of the previously used filter having some residual, 'longer half-life' radioactive contaminants? Have you ever then subjected the used filters to a closer inspection with a pancake alpha detector and consequently indeed found residual 'nasty' stuff'.


It is funny you ask this. It was not until recently that a filter I removed from my outside unit tested over background level 24+ hours after being removed. The test was done with an InspectorEXP and I plan on doing more testing on it next week.

JohnD wrote:
Maybe one possible way of 'normalizing' the measurements--in oder to take into account residual filter contaminants that could distort the daily background baseline measurement-- would be to have two of these relatively inexpensive geiger counters running in parallel, with one on a filter and one not (but have both experience the same air volume exchange), and then have the computer compute the difference between the two measurements. This concept could be extended, for example, to have three (or more) running in parallel (but possibly physically placed in-series), with and without filtration (and/or different types of filtration), etc.


What you suggest makes good sense, but I am not worried so much about small changes in the baseline... even over time. There are so many things that can change the baseline, I am looking for clear events like during rainstorm rainouts, NPP accidents and such.

_________________
MY OUTSIDE RADIATION MONITORING STATION:
South Beloit, Illinois - GMC200 Outside on HEPA air purifier, ground level, facing West.
http://netc.com/chart/view.php?n=1%3AEB5A139C


Sat Nov 23, 2013 12:17 pm
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An EneNEWS member (he lives on the West Coast) brought to my attention that he built an air purifier radiation monitoring station like mine but has had serious problems with moisture being trapped in the filter. This has been a problem for him because water acts as a shield for radiation and therefore skews his detection readings.

A friend just sent me the information below which I find really interesting and I question if the EPA "Air Cartridge Sampling" method would work better for the West Coast. I know that the test kits for radon gas in your basement are nothing more than little cans of charcoal that get sealed and mailed off to a lab for testing.

Here is more useful information about the EPA and their testing:

www.epa.gov wrote:
There are two ways of collecting samples to test for airborne radionuclides:

•Filter Sampling: RadNet stationary and deployable monitors pass air through a filter which traps particulates. The filter is sent to National Analytical Radiation Environmental Laboratory (NAREL) for a sensitive laboratory analysis that identifies the radionuclides on the particles.

•Air Cartridge Sampling: RadNet deployable monitors also pass air through a cartridge that contains charcoal. The cartridges collect radioactive particles and gases in much the same way that a home charcoal air filter traps cooking odors. The cartridges are sent to NAREL for a sensitive laboratory analysis that can detect gaseous radioactive material in the sample.

Twice weekly, monitor operators collect filters and send them to NAREL for analysis. A gross (total) beta analysis is performed on each air filter, followed by a gamma scan if the beta activity is greater than 1 pCi/m3. Each year, a composite sample of the air filters for each monitors is analyzed for plutonium (Pu-238, Pu-239, Pu-240) and uranium (U-234, U-235, and U-238).


Link to quote source:
http://www.epa.gov/radnet/about-radnet/radnet-analyses.html

_________________
MY OUTSIDE RADIATION MONITORING STATION:
South Beloit, Illinois - GMC200 Outside on HEPA air purifier, ground level, facing West.
http://netc.com/chart/view.php?n=1%3AEB5A139C


Fri Dec 27, 2013 11:25 am
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