Re: Non Ionizing Rad Question

[joseph.greco@kodak.com]

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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