WORKING WITH STATIC
MAGNETIC FIELDS
STFC SHE Code 39
Rev. 1.2, Issued August 2014
Note - This document may have been superseded by a more recent version.
Please check the SHE website for the most up-to-date version of this document.
Note - This document may have been superseded by a more recent version.
Please check the SHE website for the most up-to-date version of this document.
Revisions
1
1.1
1.2
Initial launch
Updates to audit checklist
Document Retention Policy Added
Issue Number: 1.2
Issue Date: 14/08/2014
March 2011
May 2013
August 2014
Author: Various
Page 2 of 12
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Working with Static Magnetic Fields
Contents
1.
Purpose
2.
Scope
3.
Responsibilities
4.
3.1
Managers responsible for sources of static magnetic fields >0.5mT that extend
into the working environment
3.2
Managers responsible for sources of strong static magnetic fields, >0.2T, that
extend into the working environment
3.3
STFC Staff, visitors, facility users, tenants and contractors
References
Appendices
Appendix 1: Summary of hazards associated with static magnetic fields
Appendix 2: Training
Appendix 3: Audit checklist
Appendix 4: Document Retention Policy
Issue Number: 1.2
Issue Date: 14/08/2014
Author: Various
Page 3 of 12
Note - This document may have been superseded by a more recent version.
Please check the SHE website for the most up-to-date version of this document.
Working with Static Magnetic Fields
1.
Purpose
Static magnetic fields are used in a range of applications across the STFC sites, for
example superconducting magnets in NMR machines or permanent magnets in particle
accelerator wigglers or undulators. The code aims to minimise so far as is reasonably
practicable, the health and safety risks to staff and other persons who may be affected
by static magnetic fields.
While the biological affects of strong static magnetic fields are subject to current debate
and investigation there are clear hazards associated with such fields arising from their
impact on implanted medical devices, specifically magnetic or electronic devices for
example pace makers, and their ability to attract magnetisable objects at distance and
speed (projectile and crush incidents), see appendix 1.
This code has been written to comply with The European Physical Agents
(Electromagnetic Fields) Directive (2004/40/EC amended 2008/46/EC), although the
Directive has not yet been incorporated in UK law. The Directive is currently being
reviewed, a process which may last until at least April 2012. This code will be reviewed
following incorporation of the directive in UK Law.
2.
Scope
This code applies to all static magnetic fields which extend into areas readily accessible
to people, and applies to all such fields on all STFC sites irrespective of ownership of the
apparatus generating the fields.
This code is not intended to cover every piece of equipment in which magnetic fields are
present. For example, the code is not intended to apply to electric motors, loudspeakers
and magnetrons in normal use. However, if magnets from such pieces of equipment
were removed and made into an assembly for some new purpose generating a magnetic
field extending into areas readily accessible to people then this code would apply.
This code does not address the hazards associated time varying electro magnetic fields,
see STFC SHE Code 23: Managing risks from strong time-varying EMFs.
3.
Responsibilities
3.1
Managers responsible for sources of static magnetic fields >0.5mT that extend
into the working environment shall:
3.1.1
Locate warning signs at all entrances to areas containing such magnetic fields.
Issue Number: 1.2
Issue Date: 14/08/2014
Author: Various
Page 4 of 12
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3.2
Managers responsible for sources of strong static magnetic fields, >0.2T, that
extend into the working environment shall:
3.2.1 Ensure that documented Risk Assessments address the hazards from strong static
magnetic fields, see appendix 1, SHE code 6 Risk Management. Such risk assessments
must be undertaken by individuals with sufficient expertise in such hazards (see
appendix 1), and based upon an assessment of the magnetic field based as appropriate
on: field calculations; manufacturer’s guidance; or a site survey using a calibrated gauss
meter of the magnetic field strength to determine the field contour for the strong static
magnetic field.
3.2.2 Develop and implement local procedures for the safe operation of equipment generating
the static magnetic fields, see Appendix 1.
3.2.3 Ensure that only sufficiently competent people are authorised to operate equipment and
work in the areas where strong static magnetic fields are present, and that they are
aware of the hazards, risk assessments and local procedures for the safe operation of
equipment generating static magnetic fields.
3.2.4 Ensure that warning signs and other measures, e.g. barriers or floor marks, are set up
around areas where hazards arising from static magnetic fields >0.2 T may be present.
3.3
STFC Staff, visitors, facility users, tenants and contractors shall:
3.3.1 Comply with the local procedures for the safe operation of equipment generating the
strong static magnetic fields.
3.3.2 Ensure, if any one of them has an implanted medical device such as a heart pacemaker,
that he or she informs his or her manager or other person responsible for his or her
safety before entering an area where static magnetic fields greater than 0.5 mT
(5 gauss) are present in the working environment. Anyone with an implanted medical
device may wish to contact Occupational Health or the SHE Group for advice on the
likely sensitivity of the implanted medical device to magnetic fields.
3.3.3 Report all incidents relating to strong static magnetic fields through SHE enterprise
following SHE Code 5, Incident Reporting and Investigation.
4
References
4.1
European Physical Agents (Electromagnetic Fields [EMF]) Directive (2004/40/EC
amended 2008/46/EC).
4.2
International Commission for Non-Ionising Radiation Protection (ICNIRP) Guidelines on
Limits of Exposure to Static Magnetic Fields. Health Physics 96(4):504-514; 2009 and
associated Fact Sheet, 2009.
4.3
Amendment to the ICNIRP “Statement of medical magnetic resonance (MR) procedures:
protection of patients”
4.4
NRPB Publication ‘Review of the scientific evidence for limiting the exposure to
electromagnetic fields (0-300GHz)’: Documents of the NRPB Volume 15 Number 3:
2004.
Issue Number: 1.2
Issue Date: 14/08/2014
Author: Various
Page 5 of 12
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4.5
World Health Organization (WHO), Static Fields Environmental Health Criteria
Monograph No.232.
Issue Number: 1.2
Issue Date: 14/08/2014
Author: Various
Page 6 of 12
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Appendices
Appendix 1: Summary of hazards associated with strong static
magnetic fields
a)
Physical Hazards
Collision Hazards
A danger frequently encountered in a strong static magnetic field comes from loose
magnetic objects. The field may be strong enough to attract such objects and to cause
them to fly along the field lines towards the magnet – the ‘missile effect’ or simply a
crushing effect. Therefore metallic objects, particularly magnetic objects with sharp
edges, keys, scissors, tools, gas cylinders, trolleys etc may become dangerous projectiles
and their use should be controlled in any areas where the magnetic field exceeds 0.2T.
Consideration should be given to establishing systematic search protocols before such
magnetic fields are started up to ensure that relevant areas are free from loose magnetic
objects.
Permanent Magnets
Permanent magnets, particularly rare earth magnets, can pose extra hazards since, by
their nature, they are always generating a strong static magnetic field. Extra precautions
need to be taken when handling them as the risk of pinching skin and crushing fingers is
high. The magnets should only be handled one at a time, unless special fixtures are being
used to restrain them, and non-magnetic tools should always be used in the vicinity of
permanent magnet blocks or magnet assemblies that are powered by permanent
magnets.
Movement of conducting materials in static magnetic fields
The movement of conducting materials in strong static magnetic fields can result in the
generation of eddy currents in the conductor which should be considered if assessing
hazards.
Effect on medical implants
See reference 4.2.
Persons wearing artificial metallic implants may feel painful sensations. Wearers of heart
pacemakers, for instance, should be aware of the possibility of interference from magnetic
fields.
“ICNIRP recognises that practical policies need to be implemented to prevent inadvertent
harmful exposure of people with implanted electronic medical devices and implants
containing ferromagnetic materials, and injuries due to flying ferromagnetic objects, and
these considerations can lead to much lower restriction levels, such as 0.5mT (IEC,
2002).”, ICNIRP Fact Sheet, 2009.
Issue Number: 1.2
Issue Date: 14/08/2014
Author: Various
Page 7 of 12
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b)
Biological Hazards
See reference 4.2.
Although present knowledge of the possible biological effects of strong static magnetic
fields is still somewhat uncertain, some evidence has been obtained which indicates that
simple biological systems may be affected by exposure to strong static magnetic fields.
There is no specific information regarding possible long term health effects from exposure
and none have been observed so far.
Investigations have been carried out to ascertain the effect of magnetic fields on humans,
very few have shown any effect; in one or two cases associated with high magnetic fields
it has been claimed that slight headaches, disorientation and slight feelings of nausea
have ensued especially when there is movement in a static magnetic field. The only effect
on which there appears to be some agreement is that of a taste sensation, possibly due to
loose metal fillings in teeth, when exposed to high magnetic fields.
“For static magnetic fields in excess of 2-4 T, physical movement in static field gradient
will induce sensations of vertigo and nausea that, although transient, may adversely affect
people. Together with possible effects on eye-hand co-ordination, the optimal
performance of workers executing delicate procedures could be reduced, with a
concomitant impact on safety. Other acute effects are less clearly established;
cardiovascular responses, such as changes in blood pressure and heart rate, have
occasionally been observed in volunteer and animal studies, but lie within the normal
range below 8 T.”
Health Protection Agency (HPA) website 2010
Issue Number: 1.2
Issue Date: 14/08/2014
Author: Various
Page 8 of 12
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It is therefore recommended, wherever possible, that reasonable and simple measures to
limit such exposure should be adopted, particularly exposure of the head or whole body.
Where exposure to high magnetic fields in working situations cannot be avoided then the
following ICNIRP limits (spatial peak exposure limits) should be considered:
Exposure
characteristics
Magnetic
flux
density (B)
Commentary
Occupational

Exposure of head
and trunk
2T

Exposure of limbs
8T
For specific work applications, exposure up to 8T can be justified, if the
environment is controlled and appropriate work practices are implemented to
control movement induced effects.
Public

Exposure of any
part of the body
Issue Number: 1.2
0.4T
Because of potential indirect adverse effects, ICNIRP recognises that practical
policies need to be implemented to prevent inadvertent harmful exposure of
persons with implanted medical devices and implants containing magnetic
material, and dangers from flying objects, which can lead to much lower
restriction levels such as 0.5mT.
Issue Date: 14/08/2014
Author: Various
Page 9 of 12
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Appendix 2: Training
Role
Initial Training
Managers, staff
and others
working in strong
static magnetic
fields
No specific training
is defined.
Familiarisation with
this code, through
the code launch
presentation and
the risk
assessments and
local procedures for
the safe operation
of equipment
established for
working in areas
where strong static
magnetic fields
exist.
Issue Number: 1.2
Refresher
Issue Date: 14/08/2014
Frequency
Author: Various
Comments
Page 10 of 12
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Appendix 3: Audit Checklist
Ref
Item
1
(Section 3.2.1)
Are risk assessments documented for
areas where work is undertaken in
strong static magnetic fields?
2
(Section 3.2.4)
Is the perimeter of strong static
magnetic fields marked/bounded?
3
(Section 3.2.4)
Are warning signs for the presence of
strong static magnetic fields posted at
the entrances to areas where strong
static magnetic fields are present?
4
(Section 3.1.1)
Are warning signs for the presence of
static magnetic fields greater than
0.5mT / 5 gauss posted at the
entrances to areas where they are
present?
5
Have local procedures for the safe
operation of equipment been
developed for work undertaken in
areas where strong static magnetic
fields exist?
Issue Number: 1.2
Rating
Issue Date: 14/08/2014
Author: Various
Comments
Page 11 of 12
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Appendix 4: Document Retention Policy
Records
established
Minimum retention
period
Responsible
record
keeper
location of
records
Comments/Justifi
cation
Magnetic field
Risk
Assessments
Current + 5 years
Line
Management
SHE
enterprise
SHE Group
maintain SHE
enterprise facility
Issue Number: 1.2
Issue Date: 14/08/2014
Author: Various
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