DRAFT Recommended Practice for Measurements and ...

1/29/98 71 C95.3-1991 Revision — 2 nd Draft
10/98 Draft
with the systems being surveyed. The nature of the precautions will also differ for leakage
surveys compared with measurements of deliberate radiating systems (antennas).
5.2.1 Hazards Not Directly Associated with the Survey.
Before discussing precautions directly related to the surveying process, it is worthwhile
to consider potential hazards, other than RF exposure, which might be associated with
the electronic equipment or system being surveyed.
(1) High Voltage. Electrical and electronic equipment can present potential and lethal
shock hazards. Ordinary precautions such as not defeating interlock protection
systems, exercising care around necessarily exposed high voltage leads and
terminals and avoiding working alone near high-voltage systems, should be
remembered. It is to be noted that, in many high-power systems, a prime RFleakage
source may be the high-voltage electrodes of the transmitting tubes.
Additional caution is advised when performing measurements in the vicinity of
conductive structures, such as tall cranes or long vertically suspended cables,
that are located near high-power, low-frequency RF sources. In such
circumstances, large open-circuited voltages can exist on the structures that are
exposed to ambient RF fields; these voltages may reach levels of several kilovolts
and have the potential for arcing to a grounded body, leading to strong startle
responses, and in some cases, severe RF burns. Appropriate precautions
should be exercised before contacting improperly grounded objects in strong RF
fields.
(2) X-ray Hazards. In high-power systems utilizing high-voltage transmitting or other
high- power tubes (greater than about 20 kV), there is generally the potential for X-
ray emission. It, therefore, may be desirable to first conduct a survey of X-ray
emissions before an RF survey is conducted in close proximity to such
transmitters. One should take care that the X-ray survey instrument is not
susceptible to RFI.
(3) DC Magnetic Fields. Very high-power systems may include sources of strongstatic
and low-frequency magnetic fields. Survey personnel should avoid
sustained close proximity to such sources even though definitive exposure
standards do not exist for static fields Also, tools have been known to fly out of
the surveyor’s pockets, etc., causing personnel injury.
(4) Indirect RF Hazards. It is important to remember that the presence of RF fields
can produce hazards, or at least undesirable effects, besides those arising from
exposure of body tissue. Since surveys may be conducted not only in controlled
laboratory conditions, but also near mobile transmitters, in industrial situations,
and even in homes, one should at least be aware of the following possibilities:
(a) Serious hazards are associated with the potential exposure of
electroexplosive devices (EEDs), combustible gas or flammable materials to
EM fields. ANSI/IME 20-1978 [3], (or current revision thereof), on safe
exposure distances for EED’s relative to various transmitters should be
followed.
Copyright © 1998 IEEE. All rights reserved. This is an unapproved IEEE Standards Draft,
subject to change.