[ RadSafe ] FW: Reporter's question about lowerlimitsofdetection; collection efficiency of car filters

Tue Aug 9 12:10:34 CDT 2011

Dear Al,

The collection efficiency of car air filters has been studied and the results available for the manufacturers. They are 96% efficient for particles down to 5-6microns but let the smaller ones through. These represent about 11% by mass of continental air, 89% being below this with a peak AMAD of 0.01 to 0.1microns, this is measured and published (see Christial Junge Academic Press 1963 Atmospheric Radioactivity). The different car filters were provided with histories as to where they drove and for how long. We know the engine sizes, as I have written and so we do know the level in air within quite determinable limits we know all these things. So Im sorry but you are wrong.
Cheers
Chris

-----Original Message-----
From: radsafe-bounces at agni.phys.iit.edu on behalf of Conklin, Al  (DOH)
Sent: Mon 08/08/2011 19:39
To: The International Radiation Protection (Health Physics) MailingList
Subject: Re: [ RadSafe ] FW: Reporter's question about lowerlimitsofdetection

There are so many issues with this method, I have been too dumbfounded
to think this is serious. Questions would include:
-collection efficiency of different designs of filters for a range of
particle sizes;
-particle size distribution of the plume;
-where the vehicle was at any given time- in or out of the plume (was
the car next to the plant, 30 kilometers away or all over the place?);
-Engine speed variations that can change collection efficiencies;
-Different engine sizes that would affect collection efficiencies;
-Age and dirtiness of the filters, and on and on.
I'm sorry. There's just no way. This has to be a joke.

Al Conklin
Lead Trainer and Health Physicist
Radiological Emergency Preparedness Section
Office of Radiation Protection
Department of Health
office: 360-236-3261
cell: 360-239-1237

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Brennan, Mike
(DOH)
Sent: Monday, August 08, 2011 11:25 AM
To: The International Radiation Protection (Health Physics) MailingList
Subject: Re: [ RadSafe ] FW: Reporter's question about
lowerlimitsofdetection

I can think of at least three ways of calibrating the airflow through a
filter placed on the hose of a vacuum cleaner that are more accurate in
measuring the amount of air through the filter (and hence, if you know
the efficiency of the filter in intercepting the contaminate in
question, the concentration of the contaminate per volume of air) than
these averages and assumptions about the air filter of a car.  I see no
reason to change my assumption that this particular media was chosen
because it allows manipulation of the "results" to fit the agenda of
those doing the "analysis".    

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Jeff Terry
Sent: Monday, August 08, 2011 10:46 AM
To: The International Radiation Protection (Health Physics) Mailing List
Cc: The International Radiation Protection (Health Physics) MailingList
Subject: Re: [ RadSafe ] FW: Reporter's question about
lowerlimitsofdetection

Venturi tube. 

http://www.youtube.com/watch?v=4Sz7eizKFrA&feature=youtube_gdata_player

Sent from my iPad

On Aug 8, 2011, at 12:32 PM, "Busby, Chris" <C.Busby at ulster.ac.uk>
wrote:

> When a car engine is running it works at varying rpm from 800
(tickover) to 3500 (revving).  If it is in a traffic jam and going
slowly the engine is running slowly and taking in less air. When it is
travelling fast, the engine is revving and taking more air.  The history
of these cars is known and was reported by the owners. The mileage is on
the odometer. I assumed 60km/h and 2500rpm as a mean. Actually this is
quite a good method for estimating fuel consumption on a test rig and
comparing it with average driving in town. So it is also a reliable
estimate of the air flow, since the air mix is proportional to the fuel
consumtion. In any case, the revs can only vary between 800 and 3500 rpm
so that gives an outside limit. You can assume what you like. Do the
sums and see what you get. You will always get a great deal more than
the 2.7mBq/m3 from the global fallout or the 10mBq/m3 from Chernobyl in
the N hemisphere.
> You cannot calibrate an air filter with a vacuum cleaner. What do you
mean? How would you measure the air that passed through it?
> Chris  
> 
> 
> -----Original Message-----
> From: radsafe-bounces at agni.phys.iit.edu on behalf of Brennan, Mike
(DOH)
> Sent: Mon 08/08/2011 17:03
> To: The International Radiation Protection (Health Physics)
MailingList
> Subject: Re: [ RadSafe ] FW: Reporter's question about
lowerlimitsofdetection
> 
> The number of km driven does not give you good information about how
> much air was pulled through the filter, for the simple reason that
> distance traveled in an uncontrolled environment does not correlate to
> the amount of air that was pulled through the engine.  I have, over
the
> years, made a number of trips from my home to the nearest major
airport,
> about 45 miles away.  I have made the trip in as little as 45 minutes,
> when traveling in the early morning when traffic was light.  I have
also
> made the trip in almost 2 hour during the middle of the day.  Same
> distance, very different times, gas mileage, and amount of air through
> the filter.  Additionally, the daytime trip probably had more
> particulate in the air to act as sites for contamination (including
> radioactive material) to attach to.  
> 
> Given that you could have used a vacuum cleaner with a filter over the
> hose, and calibrated the flow with little trouble, I have to admit to
> the suspicion that you chose the automobile filter specifically
BECAUSE
> of the unknowns, which you could manipulate to support your agenda.  
> 
> 
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