Non-ionizing Radiation and Electromagnetic
Fields Safety Program
Program Purpose
The purpose of this program is to provide procedures for employee and
workplace safety by identifying sources of non-ionizing radiation and
hazardous electromagnetic fields and that employees are properly
trained to work with and around these sources.
Hazards
Biological effects depend on the frequency and intensity of the
electromagnetic radiation. Known biological hazards are:
- Static magnetic fields (0 Hz) with strengths of about 4 T can produce
a variety of symptoms including nausea, metallic taste in the mouth, and
vertigo.
- Electromagnetic fields can induce the current flow in the body. The
threshold for perception and discomfort from such current flow is
frequency dependent. At frequencies from 0 Hz to 100 MHz, a serious
electrical shock can occur if the induced current flow in the body is
great enough and there is a current path from the body to ground. This
potential hazard can be assessed using a clamp-on meter available from the
Hazards Control Department.
- Radiofrequency and microwave energy can cause heating equivalent to
that in a microwave oven. Heating becomes significant at frequencies in
the MHz and GHz range, especially between about 30 and 300 MHz. Microwave
energy is known to cause cataracts and skin burns in humans.
Administrative Controls
Engineered controls (e.g., shielding and isolation) shall be used to
restrict exposure whenever practical. Signs complying with good industrial
practice, shall be posted conspicuously inside and at all entrances to areas
where hazards may exist.
Subradiofrequency Fields
The controls below apply to work areas where subradiofrequency fields
exist. These controls are based on the Physical Agent Threshold Limit Values
adopted in the Work Smart Standards set and guidelines developed by ICNIRP
- People with pacemakers shall be kept out of areas where 60-Hz electric
fields exceed 1 kV/m, as demonstrated by measurement or calculation.
Caution signs shall be posted at the entrances to these areas advising
individuals with pacemakers to keep out. However, signs are not necessary
at every inventoried source, provided measurements or calculations ensure
that the fields will not exceed 1 kV/m. Only authorized personnel may be
allowed into these areas.
- Insulating garments and equipment should be used in areas where 60-Hz
electric fields exceed 5 kV/m, as demonstrated by measurement or
calculation. Insulating gloves or, preferably, engineered controls (e.g.,
enclosure or shielding of a field source) shall be used to avoid contact
with objects that could expose personnel to sparks associated with field
strengths greater than or equal to 5 kV/m. Caution signs shall be posted
warning individuals that irritating sparks are possible. However, signs
are not necessary at every inventoried source, provided measurements or
calculations ensure that the fields will not exceed 5 kV/m.
- Insulating garments and equipment shall be used in areas where 60-Hz
electric fields exceed 15 kV/m. Controls such as access limits or
enclosures shall be considered. Warning signs shall be posted in these
areas warning individuals that irritating sparks are possible.
- People with pacemakers shall be kept out of areas where 60-Hz magnetic
fields exceed 0.1 mT (1 G), as demonstrated by measurement or calculation.
Caution signs shall be posted at the entrances to these areas warning
individuals with pacemakers to keep out. However, signs are not necessary
at every inventoried source, provided measurements or calculations ensure
that the fields will not exceed 0.1 mT.
- Areas where whole-body exposures to 60-Hz fields exceed 25 kV/m or 1
mT (10 G) shall be limited by positive means such as locked enclosures,
interlocks, or safety chains (see Document 12.1). In addition, warning
signs shall be posted in these areas. Exposures to 60-Hz magnetic fields
are permissible up to 5 mT (50 G) in the arms and legs and up to 10 mT
(100 G) in the hands and feet. Contact your ES&H Team for guidance about
frequencies other than 60 Hz.
Radio-Frequency/Microwave Radiation and Fields
The controls below apply to work areas where radio-frequency/microwave
radiation (rf/mw) and fields exist. These controls are based on IEEE
C95.1-1991 adopted in the Work Smart Standards set.
- Working time limits based on the averaging intervals specified in IEEE
C95.1-1991 shall be used when engineered controls are not practical. Note
that proven personal protective equipment is not available.
- Signs warning of rf/mw hazards shall be posted on the access panels of
irradiated enclosures of equipment and on both inside and at the entrances
to areas where individuals could be exposed to radiation or field
strengths above the safe limits. Caution signs shall be posted in
these areas, unless exposure to continuous wave rf/mw exceeds 35 times the
applicable power density or the square of the electric field-strength
limits. If magnetic fields exceed the field-strength limits, warning signs
shall be used.
- "High-hazard exclusion areas" are areas where exposure to continuous
wave rf/mw exceeds 35 times the applicable power density (or the square of
the electric field-strength limits) or where magnetic fields exceed the
applicable field-strength limits. Access to these areas shall be limited
by positive means such as locked enclosures, interlocks, or safety chains.
In addition, warning signs shall be used in the area.
- Caution signs shall be posted if radio-frequency current flows exceed
the general public levels. Warning signs shall be posted where the
radio-frequency current flows could exceed the occupational exposure
limits. Controls such as access limits or enclosures shall be considered.
Pulsed and Intense Fields
The following controls are necessary for work areas where pulsed and
intense fields exist:
- Only authorized personnel shall be allowed into areas where
pulsed-peak rf/mw or field levels exceed the limit defined by the formula
specified in IEEE C95.1-1991, where electric fields are greater than 100
kV/m, and where the rate at which whole-body magnetic fields change is
greater than 5 T/s (50 kG/s) over the whole body. In addition, warning
signs shall be posted in these areas.
- Work areas shall be regarded as high-hazard exclusion areas where
- Pulsed fields exceed 35 times the exposure limit using the following
IEEE formula from IEEE C95.1-1991:
- Electric fields exceed 200 kV/m.
- The rate at which whole-body magnetic fields change strength exceeds
35 T/s (350 kG/s).
Exposure to pulsed rf/mw shall be limited so that the ambient electric
field strength does not exceed 100 kV/m. The peak exposure shall not exceed
the following:
- In accordance with the IEEE/ANSI C95.1-1991 standard, the cw limits
and averaging times apply to situations where there are more than five
pulses during the averaging time.
Note that the following waveforms are used to determine the rate of
change of the pulsed magnetic field:
- For square waveforms, duration = tp
- For single sinusoidal waveform pulses, duration = duration of half
cycle.
- For pulse containing multiple sine waves, frequency = duration of a
half cycle of the sine waves.
Figure 1. Permissible rates of change of a pulsed
magnetic field.
These relationships are depicted as follows:
Postings and Surveys
Access to areas where nonionizing radiation sources are present shall be
limited by positive means such as locked enclosures, interlocks, or safety
chains. In addition, danger signs shall be posted in these areas.
Postings
The following equipment shall be identified on the area Hazard Notice
Door Sign:
- Steady (dc) magnets that could generate fields above 0.5 mT (5 G) to
the chest under normal-use conditions. Common horseshoe and bar magnets do
not need to be inventoried but, for example, Faraday rotators with
permanent magnets or other larger permanent magnets shall be inventoried.
A small percentage of pacemakers could malfunction in fields weaker than
0.5 mT; the most sensitive known pacemaker could malfunction in a 0.31-mT
(3.1 G) field.
- Equipment that could create 60-Hz electric fields above 2.5 kV/m or
magnetic fields above 0.1 mT (1 G). For electric fields, this is equipment
that operates above 2.5 kV without electric-field shielding between the
source and individuals; for magnetic fields, equipment that operates above
100 A. Some cardiac pacemakers can malfunction if subjected to 60-Hz field
strengths above 0.1 mT or 1 kV/m.
- All permanently installed rf gear capable of radiating over 1 W into
an open area at frequencies between 3 kHz and 300 GHz or of emitting over
100 W if the output is normally completely enclosed by coaxial cables,
waveguides, or dummy or real loads.
- All satellites and permanently installed communications transmitters.
(Receivers do not have to be listed.)
- Portable walkie-talkie communication sets capable of radiating over 7
W at frequencies between 100 kHz and 450 MHz, and over 7(450/fm)
W at frequencies between 450 MHz and 1.5 GHz (fm = frequency in
MHz units).
- All induction heaters.
- Main power-supply rooms of buildings.
Exemption from the Posting Requirement. Microwave ovens, household
appliances (e.g., refrigerators and conventional ovens), cellular phones,
and video display terminals (VDTs) do not have to be listed on the Hazard
Notice Door Sign. Likewise, storage locations do not have to be listed if
the equipment is stored such that it cannot emit energy. For example, rf
emitters would not be inventoried at storage locations. However, when in
doubt, the equipment should be listed.
Surveys
Equipment in inventory that has the potential to generate excessive
exposure to fields shall be evaluated, except for the following:
- Walkie-talkies.
- Electronic test apparatus. (Exposure to representative gear shall be
evaluated, but the equipment user and the Hazards Control Department shall
both agree about the equipment to be the evaluated.)
- Other classes of equipment. The Hazards Control Department shall
determine which classes of equipment will be exempt from evaluation based
on experience.
Whenever possible, evaluations should be made by exposure measurements
when the equipment is first set up and after significant modifications.
Equipment that is already set up, but not yet evaluated, shall be evaluated
as new equipment. The selection of appropriate measurement instruments
depends on the frequency of the electromagnetic radiation.
Training
Anyone who may reasonably expect to be exposed to fields or radiation
emitted by the equipment must be trained to have working knowledge of the
health effects of rf/mw radiation and fields and dc magnetic fields. Some
basic concepts of the physical properties are given as background for a
discussion on exposure standards and control measures.
Information about the specific hazards of equipment must be provided as
part of the safety orientation for new employees and periodic refresher
training for experienced employees. Workers shall be made aware of the
safety characteristics of the equipment they use such as frequency, pulsed
or continuous wave mode of operation, pulse duration and repetition rate
(when applicable), and output power as well as the safety guidance provided
by equipment manufacturers.
Exposure Limits
Employees and technical working contractors are covered by the controlled
access/occupational exposure criteria specified Tables A-1, A-3, and A-4 in
Appendix A. Fetuses, minors, and nonworking visitors are covered by the
uncontrolled access/general-public exposure criteria specified in Table A-3
of Appendix A.
Responsibilities
This section describes the responsibilities of personnel who work in
areas where exposure to radiation and fields covered in this document is
possible.
Employees
- Direct questions or concerns about non-ionizing radiation/fields to
your work supervisor.
- Comply with the safety controls associated with your work assignment
such as those found in Safety Plans, instructions issued by your
supervisor, or safety guidance provided in manufacturers' instructions.
- Complete training as required for your job assignment.
Responsible Individuals
- Maintain awareness of the output and safety characteristics of the
equipment such as frequency, pulsed or continuous wave mode of operation,
pulse duration and repetition rate (when applicable), and output power as
well as the safety guidance provided by equipment manufacturers.
- Ensure that workers are properly trained in the hazards and controls
for the work assigned.
- Ensure that workers comply with safety requirements.
- Before purchasing or fabricating any equipment that generates
nonionizing radiation or fields, obtain permission through the appropriate
department.
- Ensure that workers are not exposed to fields or radiation above the
levels specified in this document.
- Identify sources that are potentially hazardous.
- Evaluate exposures to nonionizing radiation and fields from equipment
use
Safety Department
- Regularly check the Hazard Notice Door Signs that indicate the
presence of nonionizing radiation sources in an area.
- Assist area supervisors and individuals planning to procure or use
nonionizing radiation and fields with evaluations, and provide guidance on
controlling exposures to these sources.
- Advise competent medical authority worker exposures to static magnetic
fields exceed limits, or where workers are exposed to subradiofrequency
and radio-frequency fields or radiation above the occupational exposure
criteria.
Radiation Safety Officer
- Provide guidance to work supervisors and workers or survey radiation
and field sources.
- Provide technical support and develop policy guidance for the safe use
of nonionizing radiation.
- Prepare and revise training materials.
Safe Work Practices
Prior to entering a room or posted area that has equipment
that transmits harmful radiation
1. Know the levels and ensure you will not exceed
allowable limits
2. De-energize and lockout equipment prior to making
adjustments
3. De-energize and lockout installed transmission
equipment prior to entering for new equipment installation.
4. Do not remain in areas of radiation transmission
for periods exceeding the work authorization time
5. De-energize transmission equipment before entering
antenna areas
6. When using a field strength tester, use on a live known
source before using it to verify a source is de-energized, to
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