[ RadSafe ] Swabbing the Bonnet (hood)

Tom Simpson bullet308 at att.net
Tue Aug 9 18:06:37 CDT 2011

A specific brand of coffee filter would be a bit better, I think.


On 08/09/2011 06:42 PM, Brennan, Mike (DOH) wrote:
> One of the most entertaining ways of calibrating a vacuum cleaner:
> (1) set up intake with filter (such as paper napkin held over hose with
> hose clamp, rubber bands, bungee cord, whatever)
> (2) attach exhaust hose (usually you have to get if from some compatible
> vacuum cleaner)
> (3) make up a good bubble mixture of soap and water.
> (4) rig a stand for the exhaust hose that hold the end a known distance
> from something sharp (actually, anything will do, but sharp looks more
> dramatic)
> (5) dip end of exhaust hose in bubble mixture, quickly clamp into rig
> (6) turn on vacuum cleaner.  Time how long it takes for the bubble to
> expand to the point and pop
> (7) calculate volume of bubble, assuming it is a sphere (it's always
> better if you can assume something is a sphere).  Using the volume and
> time, calculate flow rate in whatever units trip your trigger.
> (8) don't run the vacuum too long, or the napkin is likely to fail.
> If you can't have fun with this set up, you are just doing SCIENCE!
> wrong.
> -----Original Message-----
> From: radsafe-bounces at health.phys.iit.edu
> [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Rees, Brian G
> Sent: Tuesday, August 09, 2011 3:22 PM
> To: 'radsafe at health.phys.iit.edu'
> Subject: Re: [ RadSafe ] Swabbing the Bonnet (hood)
> Along that line, I've run a vacuum cleaner with a napkin on the nozzle
> for demos with school kids to collect Rn progeny and to do a half-life
> graphing exercise.  Just do a "calibration" just before the demo to
> determine how long to run the vacuum that day.
> Brian Rees
> ----- Original Message -----
> From: radsafe-bounces at health.phys.iit.edu
> <radsafe-bounces at health.phys.iit.edu>
> To: The International Radiation Protection (Health Physics) MailingList
> <radsafe at health.phys.iit.edu>
> Sent: Tue Aug 09 14:26:21 2011
> Subject: [ RadSafe ] Swabbing the Bonnet (hood)
> Michael Cowie wrote:
>> Why bother with the filters at all, you would have been better just
> taking a swab of the bonnet (hood for the US contingent).......think
> about that!
> Hi, Michael.
> Interesting you should write that, as I have sent some time thinking
> with the idea of how to use cars for sampling in an event.
> I like cars as a place to get deposition; certainly better than dirt or
> vegetation.  If you pick the vehicle, you can have one that was blown
> free of loose contamination prior to a known point in time (when it
> parked).  The surface usually does not absorb contamination, so anything
> that deposits is loose.  One of the things we've been playing with is
> using a slightly sticky material as a collection medium.  I was
> originally thinking post-it notes, but packing slip envelopes now seem a
> better choice.  I personally like the windshield as a sampling site, as
> it is less likely to ruin the paint job (and let's face it; if you are
> seriously sampling for radioactive deposition, the owner of the vehicle
> may already be stressed, and may not need much prompting to react
> poorly).
> A while ago a member of the public who sends me things that fan his
> fears about Fukushima (notice the alliteration?  Who says scientists
> can't be poets) sent me a link to someone talking about wiping mist off
> his windshield and counting with a radiation meter, and it was "hot"
> (this was in California in late July).  I tried the same thing here in
> Washington, and also found the mist on my windshield to be well above
> background.  However, unlike the people claiming that there was material
> from Fukushima still falling in the US, I did a decay study, and in 5
> hours it had decayed to almost background.  I concluded that all to
> almost all (note the inclusion of an uncertainty term, even in a
> qualitative description) of the activity was due to radon decay
> products.
> Anyway, I think that in the right circumstances us

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