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Section 4: Safety Guidelines and Warranty Information
4A: Safety 112
The FCC guidelines for human exposure to RF electromagnetic
fields are derived from the recommendations of two expert
organizations, the National Council on Radiation Protection and
Measurements (NCRP) and the Institute of Electrical and
Electronics Engineers (IEEE). In both cases, the
recommendations were developed by scientific and
engineering experts drawn from industry, government, and
academia after extensive reviews of the scientific literature
related to the biological effects of RF energy.
Many countries in Europe and elsewhere use exposure
guidelines developed by the International Commission on Non-
Ionizing Radiation Protection (ICNIRP). The ICNIRP safety
limits are generally similar to those of the NCRP and IEEE, with
a few exceptions. For example, ICNIRP recommends different
exposure levels in the lower and upper frequency ranges and
for localized exposure from certain products such as hand-held
wireless telephones. Currently, the World Health Organization
is working to provide a framework for international
harmonization of RF safety standards.
The NCRP, IEEE, and ICNIRP all have identified a whole-body
Specific Absorption Rate (SAR) value of 4 watts per kilogram
(4 W/kg) as a threshold level of exposure at which harmful
biological effects may occur. Exposure guidelines in terms of
field strength, power density and localized SAR were then
derived from this threshold value. In addition, the NCRP, IEEE,
and ICNIRP guidelines vary depending on the frequency of the
RF exposure. This is due to the finding that whole-body human
absorption of RF energy varies with the frequency of the RF
signal. The most restrictive limits on whole-body exposure are
in the frequency range of 30-300 MHz where the human body
absorbs RF energy most efficiently. For products that only
expose part of the body, such as wireless phones, exposure
limits in terms of SAR only are specified.
The exposure limits used by the FCC are expressed in terms of
SAR, electric and magnetic field strength, and power density for
transmitters operating at frequencies from 300 kHz to 100 GHz.
The specific values can be found in two FCC bulletins, OET
Bulletins 56 and 65:
http://www.fcc.gov/oet/info/documents/bulletins/#56;
http://www.fcc.gov/oet/info/documents/bulletins/#65