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Safety

H157655_1_008

2.2.4

Standards on Health and Safety in the Workplace

Guidelines on Limits of Exposure to Static Magnetic Fields are introduced by the ICNIRP
(International Commission on Non-Ionizing Radiation Protection). They give separate
guidance for occupational exposures and exposure of general public.

Occupational Exposures

It is recommended that occupational exposure of the head and the trunk should not exceed a
spatial peak magnetic flux density of 2 mT (20 Gauss) except for the following circumstance:

For  work  applications  for  which  exposures  above  2  mT  (20  Gauss)  are  deemed  necessary,
exposure  up  to  8  mT  (80  Gauss)  can  be  permitted  if  the  environment  is  controlled  and
appropriate  work  practices  are  implemented  to  control  movement-included  effects.  Sensory
effects due to the movement in the field can be avoided by complying with basic restrictions
set  in  the  ELF  guidelines.  When  restricted  to  the  limbs,  maximum  exposures  of  up  to  8  mT
(80 Gauss) are acceptable.

General Public Exposures

Based on scientific knowledge on the direct effects of static fields on humans, acute exposure
of the general public should not exceed 400 mT (any part of the body). However, because of
potential  indirect  adverse  effects,  ICNIRP  recognizes  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 0.5 mT (IEC 2002). The exposure limits to be set with regard to these non biological
effects are not, however, the duty of ICNIRP.

* From ICNIRP Guidelines published 2009 (http://www.icnirp.de/documents/statgdl.pdf)

European Community Directive

The European Community did release a

Directive 2004/40/EC

on the minimum health and

safety requirements regarding the exposure of workers to the risks arising from physical
agents (electromagnetic fields).

This directive, depending on the frequency, specifies the following limits of exposure to
electromagnetic fields:

Frequency Range

Magnetic Field Strength H

Magnetic Flux Density B

0…1 Hz

1.63 x 10

A/m

0.2 T or 200 mT

This specification and the following more detailed national regulations are an example that
fulfills the requirements defined and valid within the EU. Depending on the country where the
system is being installed, it is necessary to clarify the country specific or local regulations with
respect to exposure and safety in magnetic fields.

Magnetic field strength

is a vector quantity (H), which, together with the magnetic flux density,

specifies a magnetic field at any point in space. It is expressed in Ampere per metre. (A/m).

Magnetic flux density

is a vector quantity (B), resulting in a force that acts on moving charges,

expressed in (T). In free space and in biological materials, magnetic flux density and
magnetic field strength can be interchanged using the equivalence 1 A/m = 4π 10

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