01-999021-00 A0100
Installation Planning Guide
35
Chapter 5.
Stray Magnetic Fields
Sections in this chapter:
•
5.1 “Safety Hazards of Strong Magnetic Fields” next
•
5.2 “Stray Field Plots” page 36
•
5.3 “Posting Requirements for Magnetic Field Warning Signs” page 39
5.1 Safety Hazards of Strong Magnetic Fields
The potential safety hazards of strong magnetic fields to devices such as certain pacemakers
must be understood and planned for. A set of plots indicating the magnitude of the stray
fields for each type of magnet is included in
“Stray Field Plots” on page 36
. These plots
show typical levels of stray field. Actual levels may vary and should be checked with a
gaussmeter after a particular magnet has been installed.
Cardiac pacemaker wearers should refrain from entering a zone that would subject a
cardiac pacemaker to a magnetic intensity that could cause adverse effects. In some
instances, this zone might include space on the floors directly above and below the magnet.
For assistance in determining the effect of a system on a pacemaker, consult the pacemaker
user’s manual, contact the manufacturer, or confer with a physician to determine the effect
on a specific pacemaker. Actual levels vary and should be checked after a particular magnet
has been installed.
Varian provides signs warning of magnetic field hazards. Refer to
for Magnetic Field Warning Signs” on page 39
for an explanation of the types of signs and
the sign posting requirements. Additional signs are available from Varian at no charge.
Because the magnetic field exists both horizontally and vertically, the effect of the field on
persons, electronic equipment, computers, and other objects located above and below the
magnet must also be considered. Pacemaker hazard and other signs warning that a magnetic
field is present may be needed in the space on the next floor above the magnet and on the
floor below the magnet.
NMR workers are often exposed to high levels of static magnetic fields. At this time, no
conclusive evidence exists indicating adverse health effects at current exposure levels.
Current exposure levels are generally indicated as levels equal to or less than those listed in
.
Although some studies suggest a link between magnetic field exposure and adverse
reproductive effects, the body of medical data available is not clear enough to draw any firm
conclusions regarding risks to pregnancy. In other words, static magnetic field associated
with the NMR spectrometer magnets are not considered by the scientific community at this
time to comprise a risk to pregnancy or a reproductive hazard.
The American Conference of Governmental Industrial Hygienists (ACGIH) article entitled
Threshold Limit Values and Biological Exposure Indices, 5th ed., states the following:
