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Re: Non Ionizing Rad Question
There's another company called Shielding Dynamics that can do such
shielding. If you want contact info let me know and I will dig a bit for it.
Its always very expensive to shield for RF or MRI fields, so you might
want to verify the measurement, as someone else suggested.
-Gary Isenhower
On 2 Nov 2004 at 17:02, joseph.greco@kodak.com
<joseph.greco@kodak.com> wrote:
>
> Russ - the 5 Gauss limit comes from the American Conference of
> Governmental Industrial Hygienists guideline for persons with
> pacemakers and similar implanted medical devices. The 2004 TLV
> (Threshold Limit Value) from the ACGIH for an 8-hr time weighted
> average is actually 600 G for the working population.
>
> Some recommendations:
>
> -- Post the lavatory and any other area that may exceed 5 G with a
> pacemaker warning sign. There is no standard sign that I'm aware of,
> but the NMR vendor may have one (or make one yourself).
>
> -- In addition to the adjacent rooms, don't forget to survey above and
> below the NMR room. Use a proper gaussmeter for static fields (not
> time-varying fields). I have a FW Bell meter that works well. If you
> don't have one, maybe you can borrow or rent one (GE Rents may have
> them, 1-800-GE RENTS)
>
> -- Depending on the strength of the magnet, you can reach 600 G at
> several feet from the magnet. The largest hazard is from
> ferromagnetic tools and other items which can be sent flying toward
> the magnet. Also, credit card magnetic strips and watches can be
> adversely affected by the high fields. Also metallic eyeglasses
> frames. We use inexpensive plastic chain-link fencing to demarcate
> the exclusion area where people can remove watches and wallets
> (hopefully you have trusty people!) if they need close access (repair,
> maintenance, sample placement, etc).
>
> - Computer monitors can be affected by as low as 5-10 G. One
> solution is to use a flat-screen display instead of CRT (if you have
> the bucks!)
>
> -- If you really would like to pursue shielding, you can use mu
> metal. It's quite expensive and also somewhat fragile. Try Amuneal in
> Philadelphia, 800-755-9843, ask for Larry Maltin.
>
> Hope that helps. Let me know how you make out.
>
> Joe Greco
>
> _____________________________
>
> Joseph M. Greco, CHP
> Radiation/Laser Safety Officer
> Eastman Kodak Company
> Rochester NY 14652-6261
> voice: 585-588-3324
> fax: 585-588-0825
> email: joseph.greco@kodak.com
> motto: "illegitimi non carborundum"
>
>
>
> Russ Johnson
> <rujohnso@nmsu.edu> To:
> "radsafe@list.Vanderbilt.Edu"
> Sent by:
> <radsafe@list.vanderbilt.edu>
> owner-radsafe@list.van cc:
> derbilt.edu
> Subject: Non Ionizing Rad Question
>
>
>
> 11/01/2004 05:18 PM
> Please respond to Russ
> Johnson
>
>
>
>
>
>
>
> New question for the community, but a little outside the lines of
> ionizing rad. We recently had some researchers install an NMR in our
> chemistry dept. Protocols I've seen all say to establish a line of
> demarcation at 5 gauss, whereby only those operating or maintaining
> the equipment are allowed entry. However, someone supposedly took a
> meter into an adjacent lavoratory and read 30 gauss there when it was
> operating (staff apparently not from our dept). I don't know what it
> is in the lab when running, but it would certainly have to be much
> higher.
>
> So, the questions are related to how to safely control that area when
> equipment is running. Putting notice signs on the lab doors to
> restrict access just doesn't cut it. Is there any kind of "affordable"
> cost-effective shielding that could be installed to break-up or
> significantly lower the magnetic field outside the lab? Any source for
> it? Related question, what is the standard being referred to for the 5
> gauss control point? Reply on or offline Thanks. -Russ Johnson
> Rad Safety Specialist
>
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