100 Centigray (cGy) (rad) per hour, then 14 hours
Changes to the physical behavior of chemical
after the burst (7 times 2 hours), you can expect a
agents can be caused by changes in weather
reading of about 10 cGy (100 cGy divided by 10).
c o n d i t i o n s . F o r example, in cold weather,
Radiation contamination is not affected by climatic
nonpersistent agents tend to become semipersistent,
conditions or other variables that affect chemical
lasting from 2 to 10 days. Refer to FM 3-6, Field
contamination. The Army manual, FM 3-3-1,
Behavior of NBC Agents, for detailed information.
describes radiation decay rates in detail.
BIOLOGICAL
NEGLIGIBLE RISK
You must consider decon if the levels of
The many variables, involved in estimating
contamination exceed negligible risk levels.
persistency of biological hazards, require separate
consideration for each instance of contamination.
Specially trained medical personnel will consider
BIOLOGICAL AND CHEMICAL
s p e c i f i c treatment direction only after the
contamination has been specifically identified. For
example, biological agents will persist longer in cold
Negligible risk levels for biological and chemical
weather. Temperate inversions (stable conditions)
contamination are contamination that will cause mild
that exist over snowfields also tend to prolong the stay
incapacitation among no more than 5 percent of
of an aeorsolized biological cloud.
unprotected troops operating for 12 continuous hours
within 1 meter of contaminated surfaces.
RADIOLOGICAL
Measurements that determine safe levels are made
with detection equipment held 1 inch away from the
surface. For example, a one bar reading displayed on
A general idea of the persistency of radiological
the chemical agent monitor (CAM) indicates a
hazards can be gained by taking radiation dose
reduced hazard level that should be considered as a
readings. At this time, the NCF uses two types of
negligible risk level.
radioactive detection and computation (RADIAC)
instruments:
RADIOLOGICAL
1 . The AN/PDR-27 instrument provides
radioactivity detection in the lower ranges. It is
designed to detect beta radiation and measure and detect
Negligible risk levels for radiological
gamma nuclear radiation. The AN/PDR-27 is also used
contamination are measurements of 0.33 centigray
to monitor low level radiation contamination on
(cGy) or less. This level of radiation will cause no
personnel, supplies, and equipment.
more than 2.5 percent mild incapacitation to
unprotected troops.
2. AN/PDR-43 instrument provides detection of
radioactivity in the high range. It is designed to detect
beta radiation and measure and detect gamma nuclear
CONTAMINATION COMBINATIONS
radiation.
Simultaneous enemy CBR attacks will probably
NOTE: Only qualified personnel are authorized
be part of the strategy of the enemy. Risk assessments
to operate RADIAC instruments.
include consideration that the enemy may use
combinations of nuclear, biological, and chemical
For operational purposes, you can use the "7-10
weapons or may use any of these combined with
rule of thumb" to estimate future radiation levels.
conventional fire. Once CBR weapons have been
This rule provides a general estimate and should be
introduced on the battlefield, the enemy may try to
used for planning only. The rate of radioactive decay
deceive you regarding the type of hazard.
is proportional over time. The 7-10 rule means that
for seven multiples of time after the burst, the radiation
intensity will decrease by a factor of 10. For example,
The thermal effects of a nuclear blast might
if 2 hours after the burst your radiation reading is
destroy the effects of any chemical or biological
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